Johne's Disease - Why Johne's disease is so difficult to control - West DM (Proceedings of the New Zealand Society of Animal Production, 2002)
Johne`s disease caused by infection with Mycobacterium avium subspecies paratuberculosis affects New Zealand cattle, sheep, goats and deer. The disease is difficult to control because of the long incubation period, the long survival of the organism in the environment, shedding by apparently healthy but infected animals and the unreliability of diagnostic tests to detect subclinical or even clinical disease. A brief contrast with the approach to control in New Zealand and Australia is made

Karyotyping as an important screen for suitable donor cells to generate cloned and cloned transgenic animals by nuclear transfer - Olifent M; Miller AL; Beaton A; L'Huillier P; Wells DN; Laible G (Proceedings of the New Zealand Society of Animal Production, 2002)
Modern reproductive technologies are using cultured cells for the reconstruction of embryos. Cultured cells, however, can acquire abnormal karyotypes and, if not diagnosed, will compromise correct embryonic development. This manuscript briefly describes the evaluation of the karyotypes of cells used either for nuclear transfer or blastocyst aggregation to reconstruct embryos. Tetraploidy was found to be the major deviation from the normal diploid set of chromosomes. Most of the primary bovine and ovine cell lines derived from adult skin tissue contained cells with an abnormal chromosome number (75%). The percentage of abnormal cells was in the range of 0-55%. A higher proportion of clonally derived foetal cell lines had a normal karyotype (74%). Although two abnormal cell lines of this class contained only tetraploid cells, which is most likely due to the clonal nature of their derivation. In contrast, all clonal mouse embryonic stem-cell lines (four) were karyotypically normal.

Lactoferrin concentration is increased in milk from cows milked once daily - Farr VC; Prosser CG; Clark DA; Tong M; Cooper CV; Willix-Payne D; Davis SR (Proceedings of the New Zealand Society of Animal Production, 2002)
Lactoferrin is a component of milk whey, valuable for its properties as an iron-binding, bacteriostatic and anti-bacterial protein. Commonly, lactoferrin concentrations are high in colostrum and in late-lactation milk (Nonnecke & Smith, 1984). In particular, the lactoferrin content of mammary secretion is markedly increased during mammary involution when expression of the lactoferrin gene is initiated in milk-engorged, secretory alveoli (Molenaar et al., 1996). A feature of once-daily milking (OAD) is the accelerated regression of the udder that leads to an increased rate of decline in milk yield as lactation progresses (Carruthers et al., 1993). This accelerated regression and attenuation of lactation is particularly notable in some cows, although others appear relatively unaffected. In addition, there are changes in milk composition commensurate with changes that normally occur at drying-off. This suggests that milk lactoferrin concentration could be enhanced during OAD. Milk lactoferrin content has not been measured previously in cows in which milking frequency has been changed. Eight cows (mixed breeds) in mid-lactation, grazing rye-grass/white clover pasture at No. 1 Dairy, Dexcel (Ruakura) were used in this study. They were milked twice daily (TAD) from parturition and underwent a period of three days of OAD beginning at day 123±4 of lactation, on average. Mean milk SCC before treatment was 178±53 x 103 cells/ml. Milk samples were taken before, during and after OAD and assayed for lactoferrin using an ELISA method (Bethyl Laboratories, Montgomery, Texas, USA.) Milk yield and composition were also recorded.

Livestock Improvement Corporation Lecture: Animal Welfare: ethics, economics and productivity - McInerney JP (Proceedings of the New Zealand Society of Animal Production, 2002)
Ethics is about what people think, productivity relates to what useful output animals can provide, while economics is the framework within which these human and technical values get sorted out in food production and consumption. This paper offers a deliberately non-specialist overview of these issues as they relate to farm animal welfare, in an attempt to show a social science approach to what is otherwise regarded as a matter predominantly of animal science. It discusses how ethical positions concerning animal welfare link to consumer preferences, which are the driving force of economic activity, and suggests that in this context science may be informative, but not necessarily influential in determining how livestock production methods are determined. The essential conflict in livestock farming between human benefit and the animals’ wellbeing is analysed using a simple model reflecting the choices associated with different preference patterns in society. The simplistic argument that high welfare standards will raise food prices is shown to be technically correct, but the likely magnitudes are very minor. In relation to trade in livestock products, whether in domestic or international markets, the issue of animal welfare standards has ultimately to be considered in the context of satisfying consumer preferences; it should not be overly confused by emphasis on comparative costs or agricultural protection.

Liveweight gain of lambs grazing 'Ceres Tonic' plantain (Plantago lanceolata) or perennial ryegrass (Lolium perenne) - Moorehead AJE; Judson HG; Stewart AV (Proceedings of the New Zealand Society of Animal Production, 2002)
The pasture herb plantain has been successfully adapted to pastoral agriculture and, while it is readily accepted by livestock, there is little information on corresponding animal performance of regularly grazed leafy plantain forage. Liveweight gain and trace element status of lambs grazing pure plantain (Plantago lanceolata) swards and high endophyte perennial ryegrass (Lolium perenne) pastures was evaluated for 85 days during summer (December - March) under irrigated conditions. Liveweight gain was significantly (P<0.01) higher for lambs grazing plantain (222 g/head /day) than ryegrass swards (135 g/head/day) when both were offered at an allowance of 2.5kg DM/head/day. Despite a lower stocking rate on plantain swards, lamb liveweight gain expressed on a per-hectare basis tended to be greater for the plantain treatment (6.0 kg/ha/day) than for the ryegrass treatment (5.1 kg /ha/day) although this did not reach statistical significance. Lambs grazing pure plantain swards had significantly (P<0.01) higher liver copper (2250 vs 715 (µmol/ kg fresh wt) and higher liver selenium (671 vs 380 (nmol/kg fresh wt) concentrations but similar vitamin B12 (620 vs 571 nmol/kg fresh wt) concentration compared with ryegrass-fed lambs. These results indicate that well managed plantain is able to support relatively high rates of liveweight gain in lambs through summer and elevate liver copper and selenium concentrations and, therefore, could make a significant contribution to pastures in lamb finishing systems.

Managing dairy calves using continuous stocking and sward surface height - a review - Bluett SJ; MacDonald KA (Proceedings of the New Zealand Society of Animal Production, 2002)
The objectives of this review are (i) to examine the role of continuous stocking management in grazing experiments and on farm; (ii) to discuss the measurement of sward surface height; (iii) and to present experimental liveweight gain data obtained from calves continuously stocked from weaning to nine months of age. Sward height can be used as a guide in cultivar evaluations to maintain equal sward conditions between plots and treatments using put-and-take and continuous stocking management. Continuous stocking management can also be used on farm to achieve the recommended liveweight targets for dairy calves. However, further research is needed to determine the optimum sward height for calves. Weaned Friesian dairy heifers continuously stocked from November 2000 to April 2001 at Dexcel, Hamilton, and grazed to a mean sward height of 5 cm, steadily gained 0.8 kg/day, reaching a final mean of live weight of 226 kg at 9 months of age. The average stocking rate over this period was 7.1 calves/ha and the total liveweight gain was 822 kg/ha. These calves achieved the recommended liveweight targets set for replacement dairy heifers.

Milk and consumer health: review of the evidence for a relationship between the consumption of beta-casein A1 with heart disease and insulin-dependent diabetes mellitus - Hill JP; Crawford RA; Boland MJ (Proceedings of the New Zealand Society of Animal Production, 2002)
New developments in dairy foods, identifying health benefits from "functional foods" have a counterpart in claims of adverse health effects from milk components. A prime example is the present highly publicised claim of adverse effects of "A1 milk". Although there is some evidence that the consumption of beta-casein A1 may have an effect on the development of insulin dependent diabetes, other studies in this area have produced results that are inconsistent with such a claim. Some studies indicate that the removal of beta-casein A1 from the diet would have no influence on the incidence of insulin dependent diabetes. Epidemiological evidence for a relationship between the consumption of milk (and of beta-casein A1) with heart disease appears to have been a serendipitous correlation that occurred in the past perhaps due to a common underlying factor) but now no longer holds. Elimination of beta-casein A1 from the diet will have no effect on the mortality rate due to heart disease. Evidence to support claims that the consumption of the A1 variant of the milk protein beta-casein is a causative factor in heart disease and insulin dependent diabetes is therefore not sufficient to promote a change in consumer milk consumption away from dairy products containing beta-casein A1.

Modelling dairy production in different regions of New Zealand - Lile JA; Bright KP; Palliser CC; Prewer WE; Wastney ME (Proceedings of the New Zealand Society of Animal Production, 2002)
A whole-farm model is being developed at Dexcel for researchers to simulate whole-farm system trials. Climate and management information is entered and the model utilises published sub-models for pasture growth and cow metabolism. The model predicts pasture and animal production. A test of the model’s validity in different New Zealand regions using climate, land and management information particular to each region was undertaken. Regions selected were; Northland, Taranaki, Canterbury and Southland. The model predicted 92-129% of per cow milk production and, while it followed observed pasture growth patterns, there was a tendency to over-predict annual growth (5-57%) especially during spring-early summer and more notably in the Northland region. Annual pasture growth in Southland was consistently under-predicted by approximately 20%. This variation is likely due in part to differences in pasture species, soil types and the method of collecting pasture data, influencing how well the model predicted growth. Using specific climate data and management information, the model successfully predicted dairy production in most regions of New Zealand.

Monitoring onset of puberty in three genetic strains of Holstein-Friesian dairy cattle - McNaughton LR; Morgan SR; Gore P; Verkerk GA; Holmes CW; Parkinson TJ (Proceedings of the New Zealand Society of Animal Production, 2002)
Live weight and age at puberty were determined in three strains of Holstein-Friesian dairy cattle in each of two consecutive years. The strains were overseas-origin high-breeding-worth genetics (OS), New Zealand-origin high-breeding-worth genetics (NZH), and New Zealand-origin low-breeding-worth genetics (NZL), similar to the New Zealand dairy cow of the 1970s. Onset of puberty was monitored by weekly measurement of progesterone in a total of 271 heifers. Animals were considered to have attained puberty when plasma progesterone concentrations were greater than 2ng/ml in two out of three consecutive samples. Live weight at puberty differed between the strains (OS > NZH > NZL; P<0.05) but not between years. Age at puberty was affected by strain in Year 1 (OS > NZH > NZL; P<0.01), but not in Year 2. The greater live weight required to attain puberty in OS genotype animals must be recognized in target live weights for rearing of heifers.

Monitoring pain in animals using behaviour - Stafford KJ; Mellor DJ (Proceedings of the New Zealand Society of Animal Production, 2002)
The behaviour of an animal is used to identify and evaluate pain. However, simple active behaviours may not be sufficient for these purposes. Several different scales and experimental protocols have been developed for use in clinical and experimental circumstances. The use of control groups and different analgesic treatments has allowed the identification of behaviours related to particular painful stimuli. Pain threshold monitoring, self-administered analgesic trials and choice tests are furthering our understanding of an animal`s response to painful stimuli and procedures. These protocols combined with physiological, immunological and production indices are allowing for a better understanding of the effects of painful stimuli on animals. However, the interpretation of behaviour remains difficult and evaluating pain in a non-human species remains controversial.

Moving towards low-chemical farming with sheep and cattle: potential of a breeding approach - Morris CA; Mackay AD (Proceedings of the New Zealand Society of Animal Production, 2002)
On livestock farms in New Zealand, some farmers are changing their sheep, beef cattle or dairy cattle enterprises towards specialisation in low-chemical or organic systems. A vital part of the animal’s ability to perform under these systems is having the disease resistance genes available (or some other means to cope), as well as having the production and quality traits. In practice, animals are likely to be under a number of disease challenges at any one time, so breeders must concentrate their genetic selection practices on the most important health problems. Other (non genetic) means may also be critical in helping to protect the animal. This paper reviews the New Zealand evidence for genetic differences in resistance to various important diseases or metabolic stresses in sheep and cattle, and shows that genetic selection could be applied successfully if required. The paper also discusses some of the challenges in realising the goal of low chemical farming, such as finding a source of rams, bulls or semen. The diseases/stresses that are covered are: in sheep, nematode parasites, dags, fly strike, facial eczema (FE) and ryegrass staggers (RGS); in dairy cattle, mastitis, bloat, FE, RGS, nematode parasites and hypomagnesaemia; in beef cattle, RGS, nematode parasites and hypomagnesaemia. Some breed differences are mentioned, but at present the main New Zealand evidence of genetic variation is derived from heritability estimates. In sheep, average heritability estimates are: nematode parasites in lambs, 0.23 (repeatability 0.30); dags, 0.20 (repeatability 0.4); fly strike, 0.26 (Australian data); FE, 0.45; and RGS, up to 0.17, depending on the challenge level (repeatability 0.28). Corresponding heritability estimates in cattle are: clinical mastitis 0.06 (or somatic cell count 0.09); bloat 0.19 (repeatability 0.45); FE 0.56; RGS no published estimate; nematode parasites in calves 0.32; hypomagnesaemia 0.15. The simple mean of heritability estimates for 10 traits in sheep and/or cattle was 0.26 (0.28 excluding the outlier, mastitis, at 0.06), suggesting that responses should be achieved if directional selection is applied after performance or progeny testing. Knowing the genetic correlations among these disease traits is also important, because of the multiple disease challenges likely, but few of these correlations have yet been documented. Opportunities for ranking sires using the principles of Group Breeding Schemes or Sire Reference Schemes are discussed.

New opportunities to improve forage- based production systems - Marotti DM; Chapman DF; Cosgrove GP; Parsons AJ; Egan AR (Proceedings of the New Zealand Society of Animal Production, 2002)
Pasture based grazing systems in New Zealand provide many benefits such as low costs of production but there are also limitations to current high stocking rate systems. These include inconsistent quality and composition of pasture and therefore animal diet. The requirements for high production and tolerance to frequent grazing limit the number of species which can be successfully grown. The rate of productivity improvement has declined in recent years and new methods of management are needed to increase production and meet changing market requirements. Altering methods of forage presentation has been shown to improve production of milk and meat from pasture by allowing animals to achieve a high daily intake of desirable species such as clover. Further new evidence of the capacity of animals to regulate their intake toward goals other than maximizing daily dry matter intake is presented. It is argued that new opportunities for increasing grassland productivity will need to consider the behavioural responses of animals grazing pasture.

Nitrous oxide, it's formation and place in farm green house gas balances - Carran RA (Proceedings of the New Zealand Society of Animal Production, 2002)
Nitrous oxide is a troublesome greenhouse gas for New Zealand’s agricultural sector to deal with. It is formed by a naturally occurring soil process that is fundamental to the global nitrogen cycle. Quantities emitted are very small in a productive sense but very significant in New Zealand’s greenhouse gas inventory. Increasing protein production from land carries an associated risk of increasing N O emission because increased inputs of N are usually required. Attention 2 to the detail of whole system N cycling and greenhouse gas balances is therefore necessary if the challenge of increasing population and food demand is to be met without incurring hidden costs from atmospheric change.

On-farm management to modify milkfat composition - a review of experiments undertaken at Dexcel to produce a spreadable butter directly from the cow - Thomson NA; Auldist MJ; Kay JK; MacGibbon AKH; Murphy JJ (Proceedings of the New Zealand Society of Animal Production, 2002)
For many years it has been known from overseas studies that the composition and physical characteristics of milkfat are influenced by diet. The feeding of oilseeds had been shown to reduce the concentration in milkfat of short- and medium-chain-length fatty acids and to increase the concentration of long-chain unsaturated fatty acids. It was also reported that these changes resulted in softer milkfat and butter with improved spreadability at low temperatures. With this knowledge, a six-year collaborative research programme between the New Zealand Dairy Research Institute and Dexcel was undertaken to investigate the economic feasibility of producing a spreadable butter directly from the cow. The programme investigated the influence of each component in pastoral dairying that may possibly influence milkfat composition. These were: pasture, (location, defoliation interval, and species effects) on pasture lipid composition, grazed pasture effects (species and grazing rotation), supplementary feed effects (ruminally and non-ruminally protected oilseeds), frequency of feeding, and milking management. Following the study of each component the various components will be combined to develop a total farm management system to achieve the programme’s goals. The goal of producing a spreadable butter directly from the cow has been achieved, but the programme has yet to develop a profitable farm system to produce the product under existing returns for milksolids.

Organic beef in Japan - is there any room for New Zealand? - Ozawa T; Lopez-Villalobos N; Blair HT (Proceedings of the New Zealand Society of Animal Production, 2002)
In September 2001, an incident of mad cow disease (bovine spongiform encephalopathy) occurred in Japan. Japanese people now seek improved safety of beef meat and organic beef might fulfil part of this requirement. In this study, interviews were held with owners of a pasture-based beef production farm on the island of Hokkaido in Japan, which is widely recognized among the Japanese consumers as a `healthy and ecological`. The farming system is pasture-based, raising Hereford, Angus and crossbreeds, rather than the traditional Japanese Black breed. It is necessary to use grain-based concentrate feed when the animals are being finished. These feeds are fully imported, non-genetically modified, and `post harvest free feed (PHF)`. Feeding imported organic grains to cattle for fattening is contrary to the Codex organic regulations settled in 2001. Therefore, it would appear difficult to achieve domestic organic beef meat production in Japan. There are opportunities for New Zealand beef exporters to expand their market in Japan. To achieve this expansion, there are two major issues to address. Firstly, intensive market promotion to the Japanese consumer will be necessary using New Zealand`s "clean and green" image and pasture-based finishing systems. Secondly, research work is necessary to develop special beef commodities which fit the Japanese consumer`s taste.

Pain - Definition and Physiology - Johnson CB (Proceedings of the New Zealand Society of Animal Production, 2002)
Pain is defined as an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage. For a stimulus to be painful, it must be perceived consciously and found to be unpleasant. To describe how pain is transmitted from the site of stimulation to the parts of the brain responsible for conscious awareness, the term nociception is used. A nociceptive stimulus is one which will be felt as painful if and when it reaches the conscious parts of the brain. Nociceptors (pain receptors) are located throughout the body. Some are specific for pain whilst others are sensitive to things (like hot or cold) which may or may not be painful depending on the intensity. Two kinds of pain are transmitted to the central nervous system. The first is pin-prick pain. This is mild, specific to an area and is transmitted rapidly. The second is true pain. This can be severe, is only poorly localised and is transmitted to the central nervous system slowly. Pin-prick pain is the sensory arm of a valuable protective mechanism which alerts the animal to the presence of things which may cause injury. True pain can affect the function and psychological state of the whole animal and is a significant welfare issue if it is severe or prolonged. The first step in dealing with pain in animals is to recognise it. Animals are not able to communicate verbally and so cannot describe their feelings. In order to assess pain, we are forced to make assumptions about how the animal is feeling from its behaviour or physical responses. For example, if a cow is lame, it may be reluctant to walk, lame on the painful leg when it must walk, and show physiological changes in its nervous and endocrine systems. If the pain is prolonged or severe, the animal may become depressed, lose weight and show reduced productivity. Because the animal cannot say "my leg hurts", people working with animals have a responsibility to look out for signs of pain and to investigate their underlying cause.

Pain - its effects on immune function and growth in animal - Fisher AD (Proceedings of the New Zealand Society of Animal Production, 2002)
Pain, in both animals and humans, can induce wide-ranging biological consequences. In farmed livestock, two of the most important of these consequences are the potential impacts of pain on immune function and growth. In humans, the subjective experience of pain is correlated with decreases in immunocompetence and increases in the subsequent incidence of illness. In animals, procedures that can be readily assumed to be painful, and which produce behavioural and physiological stress responses, can cause immunosuppression and reductions in feed intake. Although transient pain may temporarily enhance immune function, chronic pain is immunosuppressive. The deleterious effects of pain on animal growth appear linked to the inflammatory response that accompanies tissue injury and to the direct impact of pain on feeding behaviour. The pro-inflammatory cytokines, (interleukin-1, interleukin-6 and tumour necrosis factor alpha) contribute to tissue catabolism, and act directly at the central nervous system to induce anorexia and lethargy. Although these behavioural and metabolic responses to painful conditions are adaptive in the short term, allowing the animal to rest its injury and mobilise body reserves to aid healing, ongoing pain responses have obvious negative consequences for animal productivity. Therefore, both animal welfare and productivity considerations suggest that the relief of any ongoing pain, as well as of acute pain, is important.

Pasture versus total mixed ration during the periparturient period - Roche JR; Kolver ES; Napper AR (Proceedings of the New Zealand Society of Animal Production, 2002)
The effect of diet and genotype on metabolic indicators of energy status in the periparturient cow were investigated. Fifty-six dairy cows of two different genotypes (Overseas Holstein-Friesian (OSHF) and New Zealand Holstein-Friesian (NZHF)) were randomly allocated to two dietary regimens. Half of each genotype group received a pasture/pasture silage diet pre-calving and a pasture diet post-calving, while the other half received a total mixed ration (TMR) pre- and post-calving. Compared with NZHF, OSHF had higher concentrations of plasma non-esterified fatty acids (NEFA; P<0.05) and glutamic acid dehydrogenase (GDH; P=0.09), an indicator of liver fat infiltration, 30 d post-calving. Genotype did not affect the concentration of either b-hydroxybutyrate (BHBA) or glucose in plasma. Cows grazing pasture pre-calving had greater (P<0.05) BHBA concentrations, but plasma NEFA concentration and liveweight loss during the first 30 days of lactation were not different. In summary, a pre-calving TMR did not appear to improve the metabolic energy status of the cow pre-calving. These results suggest that provided sufficient nutrients are supplied in the diet, the homeorhetic mechanisms within the cow allow adaption to very different diets. This implies that an all-forage diet pre-calving is sufficient for dairy cows fed forage post-calving.

Physiological indices of pain-induced distress - Mellor DJ; Stafford KJ (Proceedings of the New Zealand Society of Animal Production, 2002)
To date, most assessments of the pain and distress caused by dehorning of calves and castration plus tail docking of lambs have employed changes in plasma cortisol concentrations. Although this approach can aid selection of the most appropriate methods in animal welfare terms, the use of cortisol as the sole physiological index allows conclusions to be drawn only about those features of acute responses to treatment which are reflected in plasma cortisol concentrations. Accordingly, in addition to the well-established cortisol responses to these treatments, that last hours, we now report on adrenaline responses that last minutes, and noradrenaline responses with an intermediate duration are described. Blood pressure, heart rate, adrenocorticotropic hormone and cortisol responses to ring castration plus tail docking of lambs are described, and their relative sensitivity as indices of low-grade pain as the acute responses to treatment wane are considered.

Practical considerations for diagnosis and management of Cu status of deer - Wilson PR; Grace ND (Proceedings of the New Zealand Society of Animal Production, 2002)
Accurate diagnosis and appropriate management are essential for effective maintenance of an adequate copper (Cu) status of farmed deer. Deer with liver and serum concentrations below 60 µmol/kg fresh tissue and 5 µmol/L, respectively, are at risk of clinical disease or reduced growth rate. Deer with adequate serum Cu may have low liver Cu concentrations, but those with low serum Cu usually have low liver Cu concentrations. No sex differences in tissue Cu concentrations have been reported. Tissue Cu concentrations fluctuate seasonally, being lowest in late winter-early spring, and commonly with greater reduction from autumn to spring in adults than in younger deer. There is insufficient known about the Cu metabolism of deer to enable a prediction of future Cu status to be made. Analysis of forage is warranted as an aid to establish the underlying cause of deficiency and to assist management decisions. Oral Cu oxide wire particles and injectable Cu/EDTA are licensed animal remedies for Cu supplementation in deer. Treatment frequency depends on tissue concentrations, dietary factors, production goals and nutritional management. Recent research shows high rates of Cu sulphate application to pastures and grazing chicory can also elevate deer tissue Cu concentrations. Monitoring the efficacy of supplementation using changes in liver Cu concentrations is essential.

Predicting copper status of cattle remains an engima - Lee J; Knowles SO; West DM (Proceedings of the New Zealand Society of Animal Production, 2002)
Data are presented from several studies carried out by AgResearch and Massey University describing scenarios that affect the Cu status of grazing cattle. In all these studies, complex interactions between Cu, Fe, Mo and S make it difficult to predict Cu status. Increasing pasture Mo reduced percent absorption of dietary Cu in sheep by half (from 4.6% down to 2.6%). In contrast, the Cu kinetics in cattle could not be similarly simplified, so more sophisticated modelling calculations need to be applied. Even with moderate Mo intake (i.e. from pasture 0.8 mg Mo/kg DM), liver Cu content was quickly depleted in the cattle, reaching a low but stable level of 8 mg Cu/kg DM that appears to be a Mo-insensitive liver Cu store. In other trials, various Cu supplementation strategies have produced considerable but unexpected responses in liver Cu content. The risks and benefits of using liver Cu concentrations as an index of Cu status, and whether a multi-variable approach using tissue biomarkers, animal physiology, diet composition, and time of exposure is what is required to accurately predict the future Cu status for cattle are discussed.

Predicting the onset of parturition during the late gestation in dairy cows using udder scoring and hormonal profiling - Davis KL; Macmillan KL (Proceedings of the New Zealand Society of Animal Production, 2002)
Sixty-four cows were blood sampled and physical signs of impending parturition were scored daily from Day 272. Sampling and scoring ceased on Day 282 of gestation or when parturition occurred, whichever came about first. Mean udder development scores increased from 2.0 ± 0.76 (± SD) on Day -10 (ten days prior to parturition) to 3.2 ± 0.72 (± SD) on Day 0 (day of parturition) with 84% of cows having an udder score of 3 or 4 on the day prior to parturition (Day -1). Teat distension, vulva swelling and oedema were not useful as indicators of imminent parturition. Udder score was the most useful predictor, but the low frequency of scores less than 2 and greater than 3 on any one day resulted in unstable models. Plasma samples were assayed for progesterone, PGF2a metabolites (PGFM), cortisol and oestradiol. Oestradiol concentration on Day 274 was a useful predictor of whether an individual cow would calve within eight days (P=0.02). Plasma oestradiol concentrations used to build models to predict whether a cow would calve within the next five days were accurate from Day 272 to 275 of gestation (P<0.05). Progesterone, PGFM and cortisol were unreliable indicators.

Presidential Address 2001 - What is wrong with the affluent, well-fed education society in which we live and work? - Barrell GK (Proceedings of the New Zealand Society of Animal Production, 2002)
The business of food production from animals, its attendant research and technology transfer industries, and science in general are all under attack from various factions within society. Generally, we see various causes come and - like fashions - go, but recently there has been an emergence of a number of attitudinal trends that seem to be ‘ganging up’ on the animal production sector. These appear to be increasing in number and intensity. It is as if the observation that “Something is rotten in the state of Denmark.” – so bluntly voiced by Marcellus in Shakespeare’s Hamlet - could apply to some countries in the modern world, New Zealand included. As members of a society of animal production, we owe it to the livestock industry to counter these negative trends …

Producing a spreadable butter using modified milkfat - MacGibbon AKH; van der Does YE; Mabey BG; Deller GJ; Thomson NA (Proceedings of the New Zealand Society of Animal Production, 2002)
While traditional butter has been the spread of choice for many years because of the full flavour and excellent storage properties, since the advent of household refrigerators the lack of spreadability of butter when taken directly from the refrigerator has been seen as a negative characteristic. The approach taken in this study was to modify the composition of the milk from the cow through feeding trials carried out at Dexcel. However the final product must be able to be processed through a dairy plant and to have the performance that the customer requires. This means that it is not enough to know that the composition has changed but that the physical properties produced by these changes are advantageous. The goal therefore was to make the link between the properties required and to work to produce modifications that would produce those properties. This was achieved by defining the links between the product and the milkfat composition and making the physical properties such as solid fat content a target. The goal of producing a spreadable butter using modified milkfat was achieved however there is still a need to develop a profitable farm system.

Profitability of the use of new reproductive technologies in beef production systems - Smeaton DC; Vivanco WH (Proceedings of the New Zealand Society of Animal Production, 2002)
Improvements in the productivity and profitability of beef breeding cows are highly desirable despite their valuable pasture management role. New reproductive technologies could help. The present work added a gross margin analysis to a previously reported biological model. Technologies, such as embryo transfer, sex ratio control, use of small cow- large calf breeds, were tested. At commodity beef prices, use of the new technologies in beef cows appeared to be mostly uneconomic, even if biological efficiency benefits could be captured, unless embryo prices were unrealistically low. The most profitable outcome was only 11% more profitable than the status quo natural-mating system. However, profitability could be greatly enhanced if the returns on weaners born to the new technologies were greater than commodity returns. For example, at a mixed-sex embryo price ‘in the straw’ of $60 and assuming feed conversion and reproductive efficiency values similar to natural mating, use of embryo transfer broke even at $2.61/kg calf wean weight compared to a commodity return of $1.80. If ‘male only’ embryos were used, the breakeven return was $2.50. For $40 and $100 embryos, the respective breakeven premiums were 37 and 31% and 62 and 54%. The challenge, therefore, is to locate niche market returns not available to commodity production systems.

Ranking Romney sires on carcass value from a progeny test - PL Johnson; Purchas RW; Blair HT (Proceedings of the New Zealand Society of Animal Production, 2002)
Interest in the meat-producing potential of rams of dual-purpose breeds such as the Romney has increased in recent years. To cater for this a group of Manawatu ram breeders have established a progeny test to determine sire differences in carcass value (CV) estimated as the sum of the value of individual carcass parts. In 2000-2001, detailed information was collected on 139 carcasses representing 12 sires. The average carcass weight and CV (± sd) were 14.9 ± 1.9kg and $81.76 ± $10.76 respectively. A stepwise regression model with residual CV as the dependent variable was used to determine whether sire rankings on CV could be satisfactorily achieved by weighing only selected carcass parts. Weight of boneless leg (BL) explained the most variation with an r2 of 0.84. The addition of the weights of the frenched rack (FR) striploin (ST) each significantly (P<0.001) increased the amount of variation explained (r2 = 0.90), and increased the rank correlation between estimated and actual sire-group rankings from 0.71 to 0.95. A minimal model to rank the sires in this Romney progeny test is CV= -72.06+30.42*FR + 24.39*ST + 12.36*BL. Use of this model would avoid incurring the costs of weighing all carcass parts.

Recent developments in the detection and treatment of vitamin B12 deficiency in sheep and cattle at pasture - Judson GJ; Babidge PJ; Chen ZH; Sansom LN (Proceedings of the New Zealand Society of Animal Production, 2002)
Marginal Vitamin B12 deficiency is economically more important than a severe deficiency of the vitamin since the former can go unrecognised by the stockowner and hence uncorrected. This paper discusses recent work in this area by the authors, and reviews diagnostic procedures for the detection of Vitamin B12 deficiency in ruminants and developments in the treatment of this deficiency.

Reduction of tail length in New Zealand sheep - Scobie DR; O'Connell D (Proceedings of the New Zealand Society of Animal Production, 2002)
Literature evidence revealed several sources of genes that could be used to shorten the tails of sheep. Genes from the Northern short-tail group are preferable as there are no known detrimental effects on viability. Tail length from anus to tip, divided by the distance from anus to hock and calculated as a percentage was used to correct tail length for body size differences. Adjusted tail length of the progeny was best explained by additive effects for adjusted tail length of the sire (P<0.001) and dam breed (P<0.001). A small but significant interaction was also evident (P<0.01). Mean tail length was shortest for Finnish Landrace lambs (88mm) and longest for Wiltshire x Cheviot lambs (251mm). Cheviot lambs had long tails (226mm), while various crosses between Finnish Landrace and Cheviots suggest that mean tail length will be the average of the parents. The experiment suggests inheritance of a number of genes and that it will therefore be straightforward to produce genetically-docked tails using cross breeding followed by selection and interbreeding.

Reproductive state differences in analgesic related systems and their influence on learning behaviours - Cook CJ (Proceedings of the New Zealand Society of Animal Production, 2002)
Kappa-opioids exert a more powerful analgesic effect in females than in male animals. In females, this is further enhanced close to and immediately post parturition. Learning behaviour is also altered in the female around this period. Recently it was demonstrated that changes in a brain receptor subunit (part of the glutamate NMDA receptor present in all mammalian brains), termed NR2B, accompanied these periods of apparent learning enhancement. In this paper, evidence is presented for a dependence of this increase in NR2B and learning ability on Kappa-opioid systems. Pharmacological antagonism of the Kappa-opioid system during the peri-parturient period prevents both an increase in NR2B and in learning behaviour. Application of Kappa-opioids at other periods increased NR2B numbers and learning behaviour in female animals and in male castrates co-treated with oestrogen. Intact males were unaffected. The data suggests a new concept linking pain perception and processing systems to reproductive state behaviours and learning abilities.

Responses to poplar supplementation in ewes grazing drought pasture during mating - McWilliam EL; Barry TN; Kemp PD; Lopez-Villalobos N; Cameron PN (Proceedings of the New Zealand Society of Animal Production, 2002)
Over the past 160 years, poplar and willow trees have been extensively planted on New Zealand pastoral land for shade and shelter, aesthetics and conservation purposes (Wilkinson, 1999). In North Island East Coast regions, some hill-country farmers are pruning the branches of poplar and willow trees to feed them to livestock during the late summer and autumn dry period, to supplement low-quality pastures. Drought poses a serious management issue for farmers in the East Coast regions of both the North and South Islands and predictions suggest droughts will become more frequent and severe in the future (Salinger, 2000). Supplementation with conserved forages, such as hay and silages, or grains such as barley, is a common management practice for farms suffering drought conditions (Leng, 1992). However, many East Coast hill-country farms have little or no flat land on which to produce hay or silage.

Role and importance of trace elements in New Zealand livestock. Fact and fiction - Grace ND (Proceedings of the New Zealand Society of Animal Production, 2002)
In New Zealand as a result of extensive trace element supplementation animal response trials, an excellent database has been established on protocols to detect deficiencies, dietary trace element requirements, and the efficacy of many products to prevent deficiencies. However, situations still arise where the above information is not well evaluated or correctly implemented by some consultants and farmers.

Ruminant methane emission measurements and estimates - from gut to globe - Clarke H (Proceedings of the New Zealand Society of Animal Production, 2002)
Methane emissions from ruminants are New Zealand’s largest source of greenhouse gas emissions. As a signatory to the United Nations Framework Convention on Climate Change and the Kyoto Protocol, New Zealand is committed to producing an accurate inventory of its methane emissions. Official estimates of methane emissions from ruminants have declined since 1990 but because of a failure to take account of changes in agricultural productivity these figures may be misleading. In comparison to Australia, the United Kingdom and the United States of America the methods used in New Zealand to calculate methane emissions comply less well with guidelines published by the Intergovernmental Panel on Climate Change although new methodologies are under development. Estimated errors in methane inventories are large (20-80%) and although some of these errors can be reduced, large biological variation in the processes being quantified places a limit on this.

Ryegrass staggers: genetics accounts for a six-fold difference in susceptibility between selection lines of lambs at Ruakura - Aymes NC; Morris CA; Towers NR (Proceedings of the New Zealand Society of Animal Production, 2002)
Ryegrass staggers (RGS) is a neuromuscular syndrome affecting susceptible ruminants when they graze perennial ryegrass (Lolium perenne L.) containing the mycotoxin-producing endophytic fungus Neotyphodium lolii. Genetic selection for divergence in RGS susceptibility began in 1993 at Ruakura in Romney-cross sheep, with single-trait RGS selection lines for resistance (R) and susceptibility (S) being established. Stock from both lines are repeatedly challenged when grazing together on high-toxin endophyte pastures, and scored for RGS. Lambs and `yearling` females (16 to 18 months of age) have been recorded each year, as well as breeding ewes and yearling rams in some years. Results up to the 2000 lamb crop are reported here, as well as preliminary records from the 2000 born yearling females. In the 2000 born lambs (n=61), 14% and 88% of the R and S lines showed clinical RGS, respectively (P<0.01). In the 1999 yearling ewes (n=48), corresponding percentages by line were 0 and 66% respectively (P<0.01), whilst for the 2000 yearling ewes (n=18) percentages were 0 and 63%, respectively (P<0.01). Line-crosses, born and reared together with the R- and S-line animals, had levels of clinical RGS between those of the corresponding R and S lines. From restricted-maximum-likelihood analyses, the single-record heritability for RGS in all stock classes was 0.17 ± 0.02, and the repeatability (between animals across years) was 0.28 ± 0.02. Breeding value estimates suggest that most of the divergence between lines has resulted from genetic change in the S line, but the genetic mechanism is not yet clear. Reasons for this asymmetry include: (1) greater genetic and phenotypic variation in the S line than in the R line, following a given challenge; (2) greater selection intensity applied in the S line; and (3) a major gene might be present, with an allele for resistance which is recessive or partially recessive.

Salt supplementation of lactating cows - MacDonald KA; Lile JA; Lancaster JAS; Coulter M; O'Connor MB (Proceedings of the New Zealand Society of Animal Production, 2002)
Increased intensification of dairy production has contributed to a decrease in the sodium (Na) status of soils throughout New Zealand. This decline has the potential to detrimentally affect animal health and production. A trial was established to determine whether milk production responses would be obtained to sodium supplementation of cows receiving about 0.1% (0.06-0.14%) Na in pasture. The cows were in mid-lactation and were randomly allocated to either the control group or a group receiving 14 g Na/cow/day. Supplementation with 14 g Na did not increase milk yield or affect milk composition and there was no interaction with stocking rate. Serum Ca, Mg, Na, and Cl concentration were not affected by treatment, but serum K concentration decreased with Na supplementation. In summary: 0.1% Na in the diet is sufficient for mid-lactation dairy cows producing 10-12 litres milk/cow/day (0.9 kg milksolids/cow/day) and a milk production benefit will not be achieved through Na supplementation.

Seasonal variations in pasture quality on New Zealand sheep and beef farms - Litherland AJ; Woodward SJR; Stevens DR; McDougal DB; Boom CJ; Knight TL; Lambert MG (Proceedings of the New Zealand Society of Animal Production, 2002)
Nineteen sheep and beef farmers in the Waikato, Tararua, Canterbury and Southland regions collected two pre-grazing pasture samples offered to either lambs or bulls once every month from autumn 2000 to autumn 2001. One sample of pasture on offer was collected to ground level and the other was hand plucked to represent pasture selected by animals. The samples were analysed by NIRS for chemical composition and dissected into morphological components. Energy concentration of herbage was lowest in autumn and highest in spring. Energy concentrations of offered pasture were 8.1, 9.2, 7.6 and 10.0 MJME/kg DM in autumn and 10.3, 11.6, 10.8 and 11.4 MJME/kg DM in spring in Waikato, Tararua, Canterbury and Southland, respectively. Crude-protein, fibre and soluble-carbohydrate concentrations reflected the changes in ME. Variations in dead material and reproductive stem were the main causes of changes in ME. Predicted liveweight gain of 350-kg bulls grazing pasture with a pre- and post-grazing herbage mass of 2500 and 1500 kgDM/ha respectively, were 0.4, 0.8, 0.0, and 1.1 kg/d in autumn, and 1.2, 1.5, 1.4 and 1.6 kg/d in spring, for Waikato, Tararua, Canterbury and Southland regions, respectively. It is concluded that high animal performance in summer and autumn may not be achieved in summer-warm regions without the addition of high-quality forages or supplements.

Sperm oviduct-epithelial-cell- binding assay: Development of an accurate sperm-counting method using flow cytometery and an evaluation of the sources of assay variance - Krzyzosiak J; McDonald RM; Vishwanath R; Smith JF (Proceedings of the New Zealand Society of Animal Production, 2002)
Survival of sperm within the cow reproductive tract is dependant on the binding of the sperm to the oviductal epithelial cells (OEC) and is a prime determinant of fertility. An assay of sperm survival was set up using the relative binding of sperm to cultured OEC on multi-well plates. A rapid accurate method of counting sperm in the presence of OEC was developed. A precise volume of cell suspension was mixed with a known number of fluorescent micro-beads and the mixture demembranated with detergent, stained with a DNA-binding fluorescence probe and analysed by flow cytometry. Correlations were obtained between flow cytometry and spectrophotometer measurements (R2 = 0.9815, P<0.001) or manual haemocytometer counts (R2 = 0.9995, P<0.001). Sperm was loaded into a cell culture well with confluent monolayers of OEC. After incubation sperm cells remaining in suspension in the well were removed. The difference in the number of sperm in the initial sample and that removed from the well indicated the number of sperm bound to OEC. While, there were large between-well variations for the same sperm sample, the assay was still able to distinguish differences between bulls in the binding ability of their sperm. Because a minimum of 10 wells per treatment are needed to statistically detect the difference, coupled with the high effort and time requirement in preparing the culture plates, the assay is impractical for large-scale experimental assays or for routine semen assessment.

Subclinical Johne's Disease in Sheep - Thompson KG; West DM; Anderson PVA; Burnham DL (Proceedings of the New Zealand Society of Animal Production, 2002)
This paper presents preliminary results from a 5-year study aimed at generating objective data on the effect of subclinical Johne`s disease on productivity in sheep. On two properties where Johne`s disease was considered to be a problem, replacement ewe lambs from a single generation were allocated to one of three groups. One group was vaccinated with the killed Mycobacterium avium subsp. paratuberculosis vaccine Neoparasec, another with the live vaccine Gudair, and the other group remained as unvaccinated controls. The vaccinated and control ewes were monitored over the ensuing four years for the following parameters: lesion size, live weight, fleece weight, scanning percentage, lamb production and weight of lambs weaned per ewe. Serology was also performed on a sample of animals from each group. On one property, the size vaccination-site lesions associated with Gudair declined at a more rapid rate than those associated with Neoparasec. However, results to date have failed to detect a significant difference in productivity between vaccinated and unvaccinated ewes in either flock, suggesting that subclinical Johne`s disease may not be an important cause of production loss in sheep. The trial is now in its final year.

Total mixed rations versus pasture diets: Evidence for a genotype x diet on the concentration of amino acid-derived volatiles in milk - Kolver ES; Roche JR; de Veth MJ; Thorne PL; Napper AR (Proceedings of the New Zealand Society of Animal Production, 2002)
The performance of overseas (OS) and New Zealand (NZ) Holstein Friesian (HF) dairy cows were compared on an all-pasture diet (Grass) or a total mixed ration (TMR). Dietary treatments had been imposed for two years prior to the 2000/2001 season for which these results are reported. The four treatments were NZ Grass (n=14); OS Grass (n=13); NZ TMR (n=14); and OS TMR (n=14). Genotype x diet interactions were observed for annual milk yield, milksolids yield, efficiency of milksolids production, liveweight gain during lactation, and the proportion of cows not in calf. Measurement of individual cow intake using alkane markers during early, mid, and late lactation identified when these genotype x diet interactions occurred. When fed TMR, OS HF performed better than NZ HF, but on grass NZ HF performed better than OS HF. This has implications for the selection of sires for the national herd, and for the use of different dairy cow genotypes in different dairying systems.

Use of Lotus corniculatus to increase sheep production under commercial dryland farming conditions without the use of anthelmintics - Ramirez-Restrepo CA; Barry TN; Lopez-Villalobos N; Kemp PD; Pomroy WB; McNabb WC; Harvey TG; Shadbolt NM (Proceedings of the New Zealand Society of Animal Production, 2002)
Legumes are an important component of feeding systems in temperate zones to fix nitrogen and to produce high quality forage as a feed for livestock. However, marginal protein deficiency exists when ruminants are fed on fresh temperate forages due to high degradation rates of forage proteins in the rumen. Consequently, there is a large absorption of NH3 from the rumen, leaving absorption of essential amino acids (EAA) from the small intestine that is below animal requirements for these AA (Barry, 1982). Condensed tannins (CT) in Lotus corniculatus (Birdsfoot trefoil) reduce rumen protein degradability and increase EAA absorption from the small intestine (Waghorn et al., 1987). Separate feeding experiments with sheep have shown that CT in lotus increased wool production and milk secretion (Wang et al., 1996a&b) and both ovulation rate during mating, and lambing percentage (Min et al., 1999: Min et al., 2001), all with no increase in voluntary feed intake (VFI). In addition, lambs fed lotus accumulated fewer dags than lambs grazed on perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) pasture (Leathwick & Atkinson, 1995). Each of these effects was measured in separate specific experiments. The objective of this study was to assess the effect of feeding Lotus corniculatus upon wool production and lamb weaning weight under commercial dryland farming conditions without anthelmintic drench input, using a systems approach, where effects upon animal productivity and parasites were measured in the same experiment.

Vaccination against Johne's Disease - Murray A; Dupont C (Proceedings of the New Zealand Society of Animal Production, 2002)
Vaccines are important tools to aid in the control of Johne`s disease. However, currently available live and killed whole organism vaccines have a number of drawbacks including hypersensitivity reactions at the injection site and sensitization to Mycobacterium bovis antigens. These problems lead to carcase downgrading and interference with TB control programmes. Alkaline phosphatase fusion methodology is being used to search for immunogenic cell surface associated and secreted proteins of a New Zealand field isolate of Mycobacterium avium subspecies paratuberculosis. The identification of immunogenic proteins of the bacterium will facilitate the development of a subunit vaccine. This type of vaccine contains only selected components of the organism and therefore it is likely to have fewer adverse side effects. In addition, it may be possible to design a vaccine that does not interfere with TB testing programmes.

A whole-farm model applied to a dairy system - Wastney ME; Palliser CC; Lile JA; MacDonald KA; Penno JW; Bright KP (Proceedings of the New Zealand Society of Animal Production, 2002)
The complex interactions between the biological, physical and management aspects of a farm can be represented mathematically using a computer model. A whole-farm model has been developed that links published sub-models for cow metabolism together with climate-driven pasture models, in a framework that allows for different management options. The model framework is written in VisualWorks Smalltalk, with submodels written in several programming languages linked to the framework using Microsoft COM protocol. Predictions of the whole-farm model have been compared with pasture and animal production data obtained from a dairy system trial at Dexcel in the Waikato. The system consisted of a herd of 19 cows, at a stocking rate of 3.2 cows/ha. The Whole Farm Model was used with Baldwin`s MOLLY cow model of metabolism, the McCall (1984) model of pasture growth, daily climate data and a management policy whereby daily activities on the farm were enacted by the framework. These activities included, for example, assignment of paddock for grazing, closure and cutting of paddocks for conservation, calving and drying off dates of each cow, and supplement feeding. At the end of each season the whole-farm model predicted 75% of pasture growth compared with observed values assessed by visual assessment, 98% of milk yield and 98% of cow live weight. In addition to annual production by the whole farmlet, the whole-farm model can simulate individual animal and paddock production on a monthly and daily basis, so that patterns of change can be compared over the whole season. The whole-farm model is being used as a tool to design and analyse new dairy farm systems.

Winter dairy grazing systems: management practices and cow comfort - Stewart M; Fisher AD; Verkerk GA; Matthews LR (Proceedings of the New Zealand Society of Animal Production, 2002)
During winter, it is common practice to move dairy cows to a stand-off area. This project aimed to identify off-pasture management systems on farms and compare cow comfort on a variety of stand-off surfaces. A questionnaire was distributed in several dairying regions. The most common types of stand-off surfaces were concrete, or concrete in combination with another type of system. More farmers using woodchip surfaces reported that their cows laid down than those using concrete. The major health problem identified was lameness, and the majority of farmers believed that a woodchip pad worked best. Lying behaviours of 216 pregnant, non-lactating Friesian cows, on 18 farms in Waikato and Southland were recorded. Waikato cows were stood-off on woodchip pads, concrete and farm races. In Southland, covered and uncovered sawdust pads and crops were used. Cows spent longer (P<0.05) lying per day on woodchips (11.3 hrs) than on concrete (2.4 hrs) and races (4.1 hrs). Lying times for cows on covered sawdust pads (10.2 hrs) were not different from those on uncovered pads (11.5 hrs) or crops (11.2 hrs). A properly managed woodchip surface may cause less lameness and provide better opportunities for cows to rest than concrete surfaces or races.

Adapting the MOLLY cow model to fit production data from New Zealand animals - Palliser CC; Bright KP; MacDonald KA; Penno JW; Wastney ME (Proceedings of the New Zealand Society of Animal Production, 2001)
To assist in the planning of farm systems trials, Dexcel is developing a computer model of a pasture-based, rotationally grazed dairy system. The model includes published component models (or submodels) for cow metabolism and pasture growth, as well as climate and management information. It is currently being evaluated against production data obtained from the Whole Farm Efficiency Trial at Dexcel No 2 Dairy. The cow component being used is MOLLY, a dynamic model based on the underlying processes of ruminant digestion and metabolism. The parameters of MOLLY are based on animals that are efficient on high-energy diets. To make the computer model more accurate as a predictive tool for use in NZ, some of the parameters of the MOLLY submodel have been adjusted to fit the production data of NZ dairy cows on pasture, namely bodyweight changes and daily milk yields. MOLLY initially under-predicted by approximately 20% the body weight of older cows (>4 years) for the pre-calving and early lactation periods. Resetting some parameters in MOLLY significantly improved the prediction of these bodyweight changes: to 2% for the pre-calving period and 14% for early lactation. Milk yield per cow was under-predicted in early lactation by MOLLY but the fit for each cow was improved by entering the observed peak daily milk value, although further fitting is required. We conclude that MOLLY is suitable for use as a research tool to gain insights into changes in metabolism of NZ cows grazed on pasture.

Age effects and interrelationships between wool characteristics of genotypes used to develop GrowBulk sheep - Sumner RMW; Upsdell MP (Proceedings of the New Zealand Society of Animal Production, 2001)
Groups of 10 ewes of four breeds (Romney, Dorset cross Romney, Texel cross Romney, (Dorset x Romney) cross (Texel x Romney) born in two years (1994, 1995) were used to investigate the changes of wool characteristics with increasing age. Each ewe was wool sampled at hogget shearing in October and at each subsequent annual shearing in July until 1999. Romney fleeces had higher clean fleece weight, lower core bulk, longer staple length, less fibre curvature and lower crimp frequency. All genotypes exhibited similar ageing patterns for each measured wool characteristic except fibre diameter variability. Days to form a crimp increased, staple length and core bulk did not change and fibre curvature and crimp frequency decreased with increasing age. Clean fleece weight and fibre diameter increased to a plateau between 2 and 4 years of age before declining. The repeatability of all individual characteristics decreased with increasing age. There were no consistent differences in the relationship between core bulk and a combination of fibre curvature and fibre diameter across genotypes within age groups. Crossing Dorset and Texel rams over Romney ewes to generate a specialty high wool bulk composite genotype did not influence the age trends and interrelationships between individual wool characteristics inherent in the base Romney flock.

Animal production research for the shellfish aquaculture industry - Kaspar HF (Proceedings of the New Zealand Society of Animal Production, 2001)
Aquaculture is a globally significant food production industry. Aquaculture in New Zealand has grown rapidly over the past decade, and it is widely considered as an area of significant growth potential within the country’s economy. The mussel industry is the biggest sector, followed by salmon, oyster and paua. The Mussel Industry Council has a Sextant database that allows continuous interactive planning among all stakeholders and demonstrates the crucial role of R&D in the realisation of strategic goals. The industry is expected to grow at 7% pa within the next decade. This growth will require new animal production activities such as hatchery spat production, selective breeding and husbandry for animal health and condition. These activities will be based on R&D outputs such as the ability to condition broodstock, cost- effective methods for early spat rearing, and methods for the cryopreservation of gametes and embryos. To achieve these outputs, the industry supports research on the biology, ecology and genetics of the mussel, hatchery and nursery technology, shellfish selective breeding and cryopreservation, stress and disease physiology. New areas of research on shellfish production provide opportunities for the application of generic animal production expertise.

Biotechnology, farmers and the media - Taylor MJ (Proceedings of the New Zealand Society of Animal Production, 2001)
This study compared information farmers and the public are given about biotechnology, using stories from The Dominion and The New Zealand Farmer. 64% of stories were in favour of biotechnology. Biotechnology benefits made up 38% of the arguments in stories, followed by threats of not going ahead with biotechnology. Farmers were not well represented as sources. Two focus groups, one of rural producers, the other urban consumers, were asked to share their views about biotechnology. Urban consumers were more concerned about biotechnology than rural producers. Urban consumers wanted to know about dangers and safety while rural producers wanted to know about benefits. The study concluded wider debate is needed; farmers need to be actively involved; reporting needs to be more conscious; biotechnology proponents have to stop threatening people; rural producers have to understand their consumers better; and we should all ask more questions.

Black-backed gulls (Larus dominicanus) and their role in the spread of Salmonella Brandenburg - Clark RG (Proceedings of the New Zealand Society of Animal Production, 2001)
During the time sheep are aborting from Salmonella Brandenburg infection, black-backed gulls have the ability to contaminate stock water and pasture with S. Brandenburg. This enables these birds to play a significant role in the local spread of diseases caused by this organism. They also have the ability to spread other diseases, such as sheep abortions due to Campylobacter.

Can a mathematical model accurately predict intake of grazing animals? Testing the Q-Graze model - Woodward SJR; Lambert MG; Litherland AJ; Boom CJ (Proceedings of the New Zealand Society of Animal Production, 2001)
A decision support model, Q-Graze, was developed to assist farmers with grazing management decisions based on visual assessments of pasture quality. To evaluate the model’s ability to predict dry matter intake and diet composition, it was tested against pre- and post-grazing herbage mass and composition data from a trial conducted at the Whatawhata Research Centre involving bulls and steers grazing mixed-species hill pasture. Q-Graze was able to predict apparent intakes of grass leaf, grass stem, legume, weed, dead material and total dry matter with means and residual standard deviations 6.4 ± 1.5, 0.6 ± 1.3, 1.3 ± 0.7, 1.2 ± 0.8, 1.5 ± 1.4 and 10.6 ± 2.3 kg DM per animal per day, respectively. These predictions accounted for R2 = 83%, 15%, 76%, 73%, 54% and 55%, respectively of the variation in the apparent intakes calculated from the data. This indicates that Q-Graze is able to predict herbage intake and diet selection of cattle grazing mixed hill-country pastures to a high degree of correlation. The limiting factor was the measurement error of pre- and post-grazing herbage mass, rather than the model design. Model testing for additional animal and pasture types is currently being undertaken.

Changes in plasma, milk and urinary magnesium concentrations in pasture-fed dairy cows in early lactation - Thielen M; Sedcole JR; Sykes AR (Proceedings of the New Zealand Society of Animal Production, 2001)
Estimates of magnesium (Mg) balances and plasma Mg concentrations of 51 dairy cows were obtained at 2-weekly intervals from calving during the first 3 months of lactation (late August to early December). During that period estimated 24h Mg excretion increased from 1.1 to 3.2g Mg/d (P<0.001) and varied with age. Plasma magnesium concentrations in 10% of samples were below the threshold (0.6 mM) at which productivity is considered to be impaired. Within cow repeatability for plasma Mg was 0.70 ± 0.048. Individual cows showed unique patterns in the relationship between plasma Mg and estimated urinary Mg output. Mean milk Mg concentration was 104 ± 0.54 mg/l, almost 20% lower than published values used in estimates of net requirements for Mg. Individual cow repeatability for milk Mg concentration was 0.67 ± 0.082 which, together with the plasma data, suggest an important genetic component in Mg homeostasis. This will need to be accounted for in models of Mg metabolism.

A comparison of dairy farming between New Zealand and Japan - Ozawa T; Lopez-Villalobos N; Blair HT (Proceedings of the New Zealand Society of Animal Production, 2001)
The productivity and financial performance of dairy farms in New Zealand and Japan (Hokkaido) were analysed. Relative to Hokkaido, New Zealand has lower yield of milk solids per cow, but higher production per hectare because of their pasture grazing systems. The value of milk solid is much higher in Hokkaido than New Zealand (NZ$14.7 vs. NZ$3.5/KgMS), and the total expenses of producing milk solids are much higher in Hokkaido than in New Zealand (NZ$11.5 vs. NZ$3.0/KgMS). New Zealand has a lower variable cost, but higher fixed expenses and higher cash surplus ratio per farm compared with Hokkaido. There is also remarkably high interest expenditure in New Zealand caused by non-subsidised loan procurement from finance organisations. Total farm expenses per cow in New Zealand is only at about 1/10 of Hokkaido expenses. There is a marked difference in financial structures between the two countries, especially in turnover ratios of gross assets. The results suggest that it is important for dairy farmers in Hokkaido to consider not only cost savings achieved through grazing systems, but also to consider that grazing systems make only poor utilisation of capital.

Controlled Calving with induction of parturition on Day 274 of gestation in dairy cows - Davis KL; Macmillan KL (Proceedings of the New Zealand Society of Animal Production, 2001)
The response and effects of inducing parturition on Day 274 of gestation in dairy cows with synchronised conception dates was investigated in selected herds around Victoria. Cows (n=227) were injected with dexamethasone trimethylacetate (30 mg, i.m.) with 444 herdmates as controls. Randomisation was based on scored udder development. Blood samples taken on Days 272 and 274 had average plasma progesterone concentrations of 4.50 and 4.49 ng/ml respectively (P>0.05). Treated (T) cows calved an average of 2.61 ± 0.21 days before their due date, compared to 0.17 ± 0.20 days for control (C) cows (P<0.001). There were no differences in the proportion of cows displaying symptoms of milk fever, mastitis, paralysis or acute metritis. The incidence of retained foetal membranes at 12h postpartum differed between the two groups (3% vs. 16%; C vs. T; P<0.005). Control cows received more assistance at parturition (15% vs. 10%, P<0.05). There were no differences between groups for cow or calf mortality, or for any parameter of milk yield. The effect of treatment on subsequent fertility was minimal.

Correlations among beef carcass composition and meat quality traits from a genetic marker trial - Morris CA; Daly CC; Cullen NG; Hickey SM (Proceedings of the New Zealand Society of Animal Production, 2001)
A collaborative beef cattle project between AgResearch and Adelaide University is described, which had the aim of identifying genetic markers (DNA markers) for carcass composition and meat quality traits. Two extreme breeds were used, the Jersey and Limousin, and first-cross Jersey x Limousin bulls were mated to cows of both breeds to produce experimental animals in two herds, in New Zealand and Australia. The present paper provides information on relationships among some traits recorded in the New Zealand herd, with a total of 416 back-cross cattle of both sexes slaughtered as 2-year-olds at Ruakura in the springs of 1998 and 1999. The recorded data included hot carcass weight and the butcher-dissected weights of meat, fat and bone in the right side, expressed as percentages of side weight (MP, FP and BP respectively). The pH decline in the right striploin, removed from the carcass after dressing and maintained at a constant 15°C, was monitored to derive the initial (pH1), ultimate (pHu), and the rate of fall of pH. Average shear force (SAVG) and the half-life of the ageing rate (SHLF) were measured in striploin steaks cooked immediately after rigor and then at intervals until ultimate tenderness. Percentage weight loss (PWL) during cooking was recorded. Also measured in the striploin were the concentrations of three metabolic enzymes, lactate dehydrogenase (LDH), isocitrate dehydrogenase (ICDH) and 3-hydroxyacyl-Coenzyme A dehydrogenase (HAD), and the proteolytic enzymes m- and milli-calpain, and their inhibitor calpastatin (CAST). Glycogen concentration in the muscle at slaughter, expressed as the glycolytic potential (GLYP), was estimated from the sum of the concentrations at rigor of glucose, glucose-6-phosphate, lactate and residual glycogen. The range of pHu values was small, probably because all animals were regularly handled. Correlations, after adjustment for breed group, sire and slaughter group, included: MP with FP, -0.82; PWL with MP, 0.20; PWL with FP, -0.29; MP with enzymes LDH, ICDH and HAD, 0.22, -0.21, -0.03; FP with ICDH, 0.16; SAVG with SHLF, 0.48; SHLF with CAST, m-and milli-calpain, 0.28, -0.14, 0.03; CAST with m- and milli-calpain, 0.26, 0.38; GLYP with pH1 and pHu -0.01 and -0.17. Overall, HCW, MW and composition traits were not correlated with pH traits or SAVG, or m- or milli-calpain concentrations; HCW and MW were positively correlated with LDH and GLYP.

CowTrakker technology for improved heat detection - Verkerk GA; Claycomb RW; Taufa VK; Copeman P; Napper A; Kolver E (Proceedings of the New Zealand Society of Animal Production, 2001)
Devices designed to detect motion (CowTrakker™, Bou-Matic, USA) were attached to Holstein-Friesian cows of either NZ or overseas origin. Animals of each strain either grazed pasture or were fed a total mixed ration. Milk samples were collected twice weekly and progesterone content analysed to identify ovulation events. Cows had tail paint applied from 2 weeks after calving, and were observed twice daily at milking for oestrous activity. Recording continued until 6 weeks after the planned start of mating (PSM). Cows were artificially inseminated following a progesterone-based synchrony programme at PSM. CowTrakker™ data were analysed using four algorithms (T3/1, T3/3, T10/1 and T10/3), which varied according to the period of the rolling average used (3 or 10 days) and the standard deviations from that average (1 or 3). These measurements were related to behavioural observations and the occurrence of ovulation. There was a significant number of false positive events detected by the CowTrakker with all algorithms (sensitivity: 12.3, 46.9, 62.3 and 81.5%; specificity: 67.1, 88.4, 95.4 and 99.0%, for T3/1, T3/3, T10/1 and T10/3, respectively) as compared to behavioural observations alone (sensitivity: 71.6%; specificity: 99.6%). The CowTrakker™ was a useful heat detection aid, but must be used in conjunction with careful behavioural observations in order to interpret the high proportion of false positive events that are recorded.

Creep grazing, a method for investigating pre-weaned lamb diets? - Hyslop MG; Moffat CAM (Proceedings of the New Zealand Society of Animal Production, 2001)
Creep grazing as an experimental method offers potential as a research tool for investigating the diet of the pre-weaned lamb, without the confounding associated with both the ewe and lamb sharing the same pasture during lactation. Eighty- four Romney x Poll Dorset ewes with single or twin lambs were set stocked in a randomised block design (wooden gates used to create creep areas) at 15.2 ewes/ha, 4 weeks after lambing. Subterranean clover was established in four creep, and 2 shared areas in autumn. Herbage mass and composition were measured weekly in the creep and shared pasture areas.

Cryopreservation of shellfish sperm, eggs and embryos - Smith JF; Pugh PA; Tervit HR; Roberts RD; Janke AR; Kaspar HF; Adams SL (Proceedings of the New Zealand Society of Animal Production, 2001)
Cryopreservation of gametes and embryos plays a key role in the advanced areas of animal production. It will also play a central role in future aquaculture. The techniques to cryopreserve gametes are well understood in domestic animals such as sheep and cattle. In contrast, research on shellfish cryopreservation is scarce. A major limitation of previous shellfish work is that fertilisation or short-term survival has been taken as the measure of success, which has not been validated in terms of successful development and growth of larvae. This manuscript briefly describes the approach to the problem by this research team and highlights some of the similarities and differences between the procedures used with shellfish and domestic animal gametes.

Deer and pigs as hosts of bovine tuberculosis, and their potential use as sentinels of disease presence - Nugent G (Proceedings of the New Zealand Society of Animal Production, 2001)
Feral pigs and wild deer often have the highest local prevalences of bovine tuberculosis (Tb) of any of the wild animal species present in infected areas. Despite this, pigs have long been regarded as ‘spillover’ hosts that become infected mainly by scavenging infected carrion, rather than by transmission from other pigs. Deer, in contrast, appear capable of independently sustaining the disease when their densities are high, but not when they are low. Most infection in wild deer in New Zealand also appears to be spillover infection. As spillover hosts, both pigs and deer have the potential to be used as sentinels for identifying when and where Tb occurs in local possum populations. Within the constraints of local availability, pigs appear to be potentially more valuable as sentinels than deer.

Diet and genotype affect plasma calcium, magnesium and phosphorus concentrations in the periparturient cow - Roche JR; Kolver ES; de Veth MJ; Napper A (Proceedings of the New Zealand Society of Animal Production, 2001)
The literature is inconsistent with regard to the effect of diet in the periparturient period on the health and production of dairy cows, and there is little or no data on the effect of genotype. Fifty-six dairy cows of two different genotypes (Overseas Holstein-Friesian (OSHF) and New Zealand Holstein-Friesian (NZHF)) were randomly allocated to two dietary regimens. Half of each genotype group received a pasture/pasture silage diet pre-calving and a pasture diet post-calving, while the other half received a total mixed ration pre- and post-calving. Cows receiving the total mixed ration pre-calving had a lower (P<0.05) plasma calcium concentration on the day of calving and the day following calving. Conversely, cows of both genotypes offered pasture had lower (P<0.01) plasma magnesium and phosphorus concentrations pre- and post-calving compared with cows fed a total mixed ration. OSHF cows had lower plasma calcium (P<0.05) and magnesium (P<0.001) concentrations post-calving. Plasma phosphorus concentrations were unaffected by genotype. Herds with a high proportion of OSHF genetics are at an increased risk of parturient hypocalcaemia and hypomagnesaemia. Recommended daily allowances for these minerals may need to be increased to allow for this predisposition.

Digestion kinetics of mature grasses - Chaves AV; Waghorn GC; Brookes IM; Burke JL (Proceedings of the New Zealand Society of Animal Production, 2001)
Digestion kinetics were measured for mature (green and non-senescent) components of five grass species using in sacco and in vitro incubations to define rates of degradation and nutrient release. The data will be incorporated into a dairy nutrition simulation model to identify limitations in nutrient supply to cows grazing mature pasture in late spring. Perennial ryegrass, tall fescue, Yorkshire fog, phalaris and paspalum were hand separated into leaf, stem and inflorescence for incubations. Percentages of fibre (NDF) in DM fractions ranged from 50-69% (leaf), 63-75% (stem) and 50-68% (inflorescence). Crude protein concentrations in the DM of the respective fractions were 7.5-23.7%, 3.8-8.3% and 7.9-12.3%. Soluble DM (% of the total) determined after mincing accounted for 31-53% of leaf, 26-55% of stem and 20-48% of inflorescence, and fractional (h-1) degradation of the insoluble DM was very slow, ranging from 0.034-0.113 (leaf), 0.025-0.036 (stem) and 0.033-0.072 (inflorescence). After 24 hours of in vitro incubation plant nitrogen content become limiting for fermentation in most instances.

Early indications that feeding Lotus will reduce methane emissions from ruminants - Woodward SL; Waghorn GC; Ulyatt MJ; Lassey KR (Proceedings of the New Zealand Society of Animal Production, 2001)
Ruminant livestock produce at least 75% of New Zealand’s total methane emissions and are a major contributor of greenhouse gas emissions. Most ruminant methane arises from microbial activity in the rumen (methanogenesis) and is released through the mouth and nose. Methane production per unit feed intake or per unit production can be reduced by improving diet quality, for example, including legumes in a pasture diet. A preliminary investigation with wether sheep showed lower daily methane outputs per unit dry matter intake (DMI) when fed Lotus pedunculatus (a condensed tannin-containing legume) than ryegrass-based pasture or lucerne (14.5 vs. 20.4 vs. 19.0 gCH4/kg DMI). Friesian dairy cows fed either Lotus corniculatus silage or perennial ryegrass silage had similar total methane outputs (376.7 vs. 344.4 g CH4/cow/day; ns). However, methane emissions were lower from cows fed Lotus silage when expressed per unit DMI (26.90 vs. 35.13 g CH4/kg DMI; P<0.001) and per unit production (378 vs. 434 g CH4/kg milksolids; P<0.05) as a result of the higher intake and milksolids yield. The mitigation of methane emissions from animals fed Lotus species was due in part to a higher nutritive value relative to pasture but effects of condensed tannins on methanogenesis warrants further investigation.

The effect of condensed tannins in sainfoin (Onobrychis viciifolia) and sulla (Hedysarum coronarium) on the digestion of amino - Bermingham EN; Hutchinson KJ; Revell DK; Brookes IM; McNabb WC (Proceedings of the New Zealand Society of Animal Production, 2001)
Two experiments were conducted in order to compare the effect of condensed tannins (CT) in sainfoin (Onobrychis viciifolia) and sulla (Hedysarum coronarium) on the flux of amino acids (AA) through the gastrointestinal tract of sheep. In each experiment, one group of sheep (PEG group; CT inactive) received an intraruminal infusion of polyethylene glycol (PEG) to inactivate the CT present in the forages, while the other group received an intraruminal infusion of water (Tannin group; CT active). The CT in sainfoin (38.1 g/kg DM) had no significant effect on apparent AA absorption from the small intestine. However, in the sulla-fed sheep, AA absorption in the small intestine was significantly increased by CT (P<0.05; CT = 64.4 g/kg DM). In both forages a shift in AA digestion from the rumen to the small intestine was seen with increased abomasal fluxes of AA in the Tannin group of sainfoin- (92 versus 101 g/day in the PEG and Tannin group, respectively; P<0.05) and sulla-fed (65 versus 83 g/day; P<0.001) sheep. Differences in the digestion and absorption of AA in the two forages may be associated with differences in chemical structure of the CT.

Effect of grain or buffer supplementation on milk solids yield and rumen fermentation patterns of cows grazing highly digestible herbage in spring - Dalley DE; Roche JR; Grainger C (Proceedings of the New Zealand Society of Animal Production, 2001)
Sixteen rumen-fistulated Holstein Friesian cows in early lactation were offered 40 kg herbage dry matter (DM)/cow/day (to ground level). The objective of the experiment was to investigate the economics of feeding cereal grain supplements to cows grazing highly digestible ryegrass herbage in spring and determine the impact of grain feeding on rumen conditions and milk composition. Six kilograms DM of cereal grain were offered to eight cows, while the other 8 cows did not receive grain. Superimposed on these grain supplementation rates were 0 or 300 g sodium bicarbonate in a 2x2 factorial design. The inclusion of grain in the diet reduced herbage intake (from 16.7 - 12.7 kg DM/day, P<0.01) and the neutral detergent fibre concentration of the total diet (from 410 g/kg - 325 g/kg DM). Grain feeding reduced milk fat concentration (from 41.7 - 34.3 g/kg, P<0.05) and increased milk protein concentration (from 32.8 - 34.6 g/kg, P<0.05). Grain feeding depressed the rumen fluid concentration of acetic acid and increased that of propionic acid, resulting in a lipogenic:glucogenic ratio (acetic + butyric:propionic acid ratio) below 3:1 for both grain treatments. The milk responses from cows consuming concentrates with highly digestible herbage in spring were low (-0.4 - 0 kg 4% fat corrected milk/kg DM grain consumed) and did not improve the returns to farmers during the period of feeding. The most profitable use of concentrates is likely to come after spring calving cows have reached their peak and herbage quality begins to decline.

Effect of incorporating East Friesian genes on wool characteristics - Reid TC; Booker J (Proceedings of the New Zealand Society of Animal Production, 2001)
A study carried out on eight farms examined the effect of crossing the present flock (Corriedale or Romney) with East Friesians. Crossing East Friesian over Corriedales increased fibre diameter from 28.5±0.1 µm to 31.7±0.2 µm compared with straightbred Corriedales. Inclusion of up to ¾ East Friesian breeding over Romneys reduced the fibre diameter from 36.3±0.4 µm to 31.4±1.3 µm compared with straightbred Romneys. The effect on bulk of crossing East Friesians over Corriedale was variable. Based on an average wool price of 500c/kg clean for 28 µm Corriedale hogget fleece wool between 94/95 and 98/99, a change of 3.0 µm is likely to reduce the expected wool price by approximately 7%. Based on an average wool price of 400 c/kg clean for 36 µm Romney hogget fleece wool, a change of 4.0 µm is likely to increase the expected wool price by approximately 13%.

Effect of premating iodine supplementation of ewes fed pasture or a brassica crop prelambing - Grace ND; Knowles SO; Sinclair GR (Proceedings of the New Zealand Society of Animal Production, 2001)
On two sheep farms with different winter feeding systems, namely pasture only (farm A) or pasture then swedes or swedes/turnips/kale for 6 to 8 weeks prelambing (farm B), 700 ewes/farm were randomly assigned to 2 groups of 350 animals to assess animal performance. About 5 weeks premating, one group was injected with 390 mg iodine (as Flexidine iodised oil) intramuscularly. Iodine supplementation increased and maintained serum and milk I concentrations for at least 210 days (µg/L; farm A, serum 43 v 65; milk 72 v 197. Farm B, serum 29 v 45; milk 26 v 132), but did not affect potential lambing percentage at scanning, perinatal mortality, or lambing percent (farm A, 140 v 150%; farm B, 138 v 130%). On farm A no goitre was observed among the 77 lambs postmortemed, regardless of I treatment of the ewes. On farm B goitre was observed in 85% of the 34 lambs postmortemed from untreated ewes, but not among the 36 lambs from treated ewes. In the following year, the trial was repeated with 50 ewes/group to monitor changes in I status, and the treatment significantly increased serum I over time but had no consistent effect on serum T4 and T3 concentrations. Supplementing ewes premating with long-acting injectable I prevented goitre in newborn lambs from ewes fed swedes or swedes/turnips/kale as a winter supplement.

Effect of stage of lactation on the efficiency of Jersey and Friesian cows at converting pasture to milk production or liveweight gain - Thomson NA; Kay JK; Bryant MO (Proceedings of the New Zealand Society of Animal Production, 2001)
A study comparing Jersey (J) and Friesian (F) cows in early (EL), mid (ML) and late (LL) lactation and offered either ad libitumpasture (P) or restricted pasture allowance + a concentrate (PC) was conducted. Breeds were grazed at a similar live weight (LWT)/ha (1340 and 1850 kg LWT/ha for P and PC respectively). F cows produced 10% more MS/cow/day than J cows. DM intake (DMI) on P was 13.6 kg DM/cow/day for F and 11.3 kg DM/cow/day for J cows but if expressed at constant LWT, J consumed more than F cows (30.3 versus 28.0 + 0.8 g DMI/kg LWT). During EL, J cows gained less live weight than F cows but in LL the reverse occurred. An interaction between breed and stage of lactation also occurred for the conversion efficiency of pasture DM to milkfat, protein, casein and MS. For the yield of milkfat, protein and casein J cows in EL were more efficient than F cows but in LL no breed effect on the conversion efficiency of pasture to these components occurred. The difference between breeds in partitioning feed to milk solids and liveweight gain at different stages of lactation suggests different management opportunities for each breed to more efficiently convert pasture to MS.

Effects of insulin on amino acid uptake by the mammary gland of the pasture-fed lactating ruminant - Back PJ; Davis SR; MacKenzie DDS; Harris PM; Roy NC; Lee J (Proceedings of the New Zealand Society of Animal Production, 2001)
Twelve lactating ewes housed indoors were allocated to one of two treatment groups (hyperinsulinaemic euglycaemic clamp (HEC) or control) in a randomised block design experiment. Mammary amino acid uptake from plasma and utilisation for milk protein synthesis was measured during the fourth day of the HEC using the arterio-venous concentration difference (A-V) technique. There was no change in milk protein output during the HEC (P>0.05). The HEC induced a significant decrease in arterial concentrations of all essential amino acids (EAA) except for histidine and an increase in the extraction efficiency of isoleucine (HEC, 61 ± 3% vs. control, 52 ± 3%, P<0.05) and leucine (HEC, 64 ± 3% vs. control, 53 ± 3%, P<0.05). There was no significant change in extraction efficiency of other EAA or mammary blood flow. The ratio of amino acid uptake from plasma to output in milk protein suggested deficits in uptake for some EAA in both treatments, especially histidine. These results indicate that the mammary gland can adapt to a changing arterial supply of amino acids to maintain milk protein output by increasing extraction efficiency and/or a greater reliance on amino acids supplied by erythrocytes and/or plasma peptides.

Evaluation of an oestrone sulphate dipstick immunoassay for pregnancy testing mares - Stewart J; Henderson K (Proceedings of the New Zealand Society of Animal Production, 2001)
Serum samples from 213 mares were received for routine pregnancy testing and analysed by a conventional oestrone sulphate (OS) enzymeimmunoassay (EIA) and a new OS dipstick immunoassay. OS concentrations, measured by EIA, in 122 of the samples were <10 ng/ml, indicating the mares were not pregnant. The same 122 samples also returned a `not pregnant` diagnosis when analysed by the dipstick immunoassay. The remaining 91 samples returned diagnoses of `pregnant` by the OS EIA, i.e., OS concentrations were >20 ng/ml. Of these, 89 also returned a `pregnant` diagnosis by the dipstick assay, but 2 returned a `not pregnant` diagnosis. Both these mares were found to be pregnant on follow up, indicating that the dipstick test had returned a false negative diagnosis in each instance. These results show that there is 100% agreement between the conventional OS EIA and the new dipstick assay in diagnosing `non pregnancy`. However, the dipstick assay may return a small proportion (2.2%) of false negative diagnoses relative to the EIA. Overall, the new dipstick immunoassay offers a practical alternative to the OS EIA for diagnosing pregnancy status in mares.

Experimental infection of pregnant sheep with attenuated Salmonella typhimurium - Khalil AM; McFarlane RG; Shand NA; Leslie SE; Christensen NH (Proceedings of the New Zealand Society of Animal Production, 2001)
Salmonellosis occurs in many animal species including sheep, and may cause pathology of the gut and possible abortion. If attenuated strains were to be used for future control, their establishment in the host and shedding pattern needs to be determined. Fifty-one pregnant ewes were obtained from the Lincoln University Research Farm and assigned randomly to five treatment groups. At approximately 1 month before lambing, the groups were given attenuated S. typhimurium (cya-, crp-) by different routes and doses as follows: 1010 colony-forming units (cfu) intranasally (i.n.), 109 cfu i.n., 1010 cfu subcutaneously (s.c.), 109 cfu s.c., and control (saline i.n. and s.c.). Selected animals were slaughtered at days 4 and 14 post infection for bacteriological culture from the mesenteric and retropharyngeal lymph nodes, intestinal contents and lamb stomach contents. The experimental organisms were isolated using selective cultures and identified by latex agglutination test and fermentation reactions. Following infection there were no changes in rectal temperature or significant clinical signs except two cases of abortion in the 1010 cfu s.c. group. The number of animals shedding organisms in their faeces decreased with time from 12 ewes at day 1 to one ewe at day 4 and day 7. Most of them were from the 1010 i.n. group. Subcutaneous injection of 1010 cfu induced abortion in two of 11 ewes, as organisms were detected in their faeces and the aborted lambs. However, no organisms were detected in faeces, intestinal contents or the lamb stomach contents of the ewes that were killed at days 4 or 14. In the two ewes that had received 1010 cfu i.n. and were killed at day 4, organisms were detected in the mesenteric and retropharyngeal lymph nodes. In summary, the administration of the attenuated S. typhimurium (cya-, crp-) at 1010 cfu caused asymptomatic short-term faecal shedding and abortion when given i.n. and s.c., respectively.

Factors associated with the incidence of 'Phantom cows' in Australian dairy herds - Nation DP; Morton J; Cavalieri J; Macmillan KL (Proceedings of the New Zealand Society of Animal Production, 2001)
A major cause of delayed pregnancy and reproductive wastage in Australian dairy cattle is the failure of cows to be re-inseminated within 24 days of an unsuccessful insemination. Four commercial herds were observed to determine the incidence of this syndrome. Those cows inseminated in the first three weeks of the mating season (n=721 cows) were observed for a subsequent return to service, and non-return cows were diagnosed for pregnancy. Overall, 45% of cows were confirmed pregnant to first service, 37% returned to service within 24 days, and 19% were diagnosed as non-return, non-pregnant cows (Phantom cows). The majority of cases of Phantom cows (89%) were explained as having: a) a CL but not returning for service; b) having an abnormally long return to service (25 to 39 days); or, c) reverting to an anoestrous state. Other cases (<5% incidence) included ovarian cysts, pyometra and uterine adhesions. Repeated diagnoses of pregnancy identified few cases in which a pregnancy appeared to have failed (3.3%). The incidence of Phantom cows was higher for CIDR-treated anoestrous cows than cows synchronised with prostaglandin, and lowest for those cows not treated. These observations form the basis for further study of this syndrome in Australian herds.

The farming of game species .... horses for courses - Asher GW; Pearse AJ (Proceedings of the New Zealand Society of Animal Production, 2001)
Pastoral-based animal industries utilise only a handful of domesticated species. The relatively recent development of farming "game" species (i.e., species traditionally harvested by hunting) has been largely prompted by changing first-world consumer demographics. Pastoral farming of red deer in NZ is often seen as a glowing example of diversification away from traditional livestock. In tropical regions, specific species adapted to local climate, vegetation and diseases include axis deer, sambar deer and rusa deer. In the arctic regions, reindeer are the species of choice due to their cold tolerance and food selection habits. Various species (e.g., antelope, buffalo, elephants, zebra, etc) form the basis of a growing game ranching industry in the dry savannah regions of Africa, structured around sustainable, low-density, multi-species grazing of rangelands that are generally unsuited to domestic livestock due to aridity or parasites/diseases (e.g., tsetse fly). Thus, there are many examples of successfully picking "horses for courses" ... game species suited to particular environments. Conversely, there is a danger that in the enthusiasm to promulgate particular systems around the world, there are occasions when "horses are on the wrong courses". Classic examples for this include attempts to farm (1) tropical species in temperate environments, (2) temperate species in tropical environments, and (3) species behaviourally and physiologically misaligned with pastoral environments.

Feed intake capacity in Holstein-Friesian cows which differed genetically for body weight - Caicedo-Caldas A; Lemus-Ramirez V; Holmes CW; Lopez-Villalobos N (Proceedings of the New Zealand Society of Animal Production, 2001)
The feed intake capacity (FIC) of pregnant, non-lactating Holstein-Friesian cows, selected for either high (H) or low (L) breeding values for live weight (LW), was measured when fed to appetite on hay (7.5 MJ ME/kg DM in 1998) and on pasture (11.1 MJ ME/kg DM in 1999). The H cows were heavier than the L cows in both years (546 v 482 kg; 540 v 464 kg in years 1 and 2 respectively), and the H cows ate significantly (P<0.01) more feed than the L cows in both years (12.5 v 11.1 kg hay DM, and 13.1 v 11.6 kg pasture DM per day in years 1 and 2 respectively. Regression analysis showed that for each 100-kg increase in LW, daily DMI per cow increased by 1.43 and 1.81 kg respectively in 1998, and 1999. Regression analysis of the data after conversion into log10 , showed that DMI was proportional to LW0.66 and LW0.65 in 1998 and 1999 respectively. These results indicate that the genetically heavier cows ate more DM than the genetically lighter cows. Nevertheless, the difference between maintenance costs and FIC (or "net" FIC) may be similar for both strains, so that the smaller intake of the lighter cows does not disadvantage their productive capacity.

Ferrets as vectors of bovine Tb in New Zealand: a review - Byrom AE (Proceedings of the New Zealand Society of Animal Production, 2001)
Feral ferrets (Mustela furo) are a serious pest of agricultural importance because they transmit bovine tuberculosis (Mycobacterium bovis ; Tb) to domestic livestock. They therefore pose a significant risk to New Zealand’s international trade in dairy, beef and venison products The most likely route of infection to ferrets is oral, through killing and eating infected prey or scavenging infected carrion (particularly possums). Indeed, the prevalence of Tb in ferrets is positively correlated with possum abundance and infected possums. Male ferrets have a higher prevalence of Tb than females, and adult ferrets have higher prevalence than juveniles. It is still not clear whether Tb can cycle independently in feral ferrets in the absence of external (non-ferret) sources of infection (i.e., “maintenance hosts”) or whether the disease is simply “spillover” infection from other wildlife populations (predominantly possums). Available evidence suggests that ferrets are more likely to be spillover than maintenance hosts in most habitats in New Zealand. However, several aspects of the epidemiology of Tb in feral ferrets, and the ecology of feral ferrets, need to be investigated in order to resolve this debate.

The film crew's here! Are you ready? - Tompkins NB (Proceedings of the New Zealand Society of Animal Production, 2001)
The Reporter/Directorcontrols the story line and ‘angle’ (direction) the story will follow. They question the ‘talent’ (the scientist) and decide on what ‘shots’ (pictures) will be used to illustrate the words in consultation with director of photography. The Director of Photography/Camera Operatorwill make sure you are in focus, set up the framing of the picture and lighting and control the picture quality. The Sound Operatorwill capture all the sound, from interviews to lambs bleating and computers that go ‘bing’. The sound operator controls sound quality - they don’t like airport flight paths or lawnmowers! These people are mostly ‘freelancers’. That is, they usually don’t work for the actual film/production company. The standard filming day is 10 hours plus a 45-minute lunch break. Many of them like coffee and most smoke.

Genetic studies of resilience of Romney sheep to nematode challenge in New Zealand - Morris CA; Bisset SA; Vlassoff A; Mackay AD; Betteridge K; Alderton MJ; West CJ; Devantier BP (Proceedings of the New Zealand Society of Animal Production, 2001)
"Resilience" in sheep can be defined as the ability to withstand nematode challenge, and to maintain acceptable health and productivity, with minimal reliance on anthelmintic treatment. One heritable component trait is Total Drench Requirement (TDR), which is measured in lambs managed on a regime of "drench-on-demand" (where Trichostrongylus and Ostertagia are the predominant nematode genera in New Zealand sheep). A breeding experiment was established in 1994, selecting for increased resilience in Romney lambs. Currently, breeding ewes in the experiment are subdivided between Ballantrae, where four genetically equivalent sub-groups graze separate farmlets year-round, under Non-Chemical versus Conventional management (AgResearch’s Low-Chemical Farming Systems Programme), and Wallaceville, where an Elite Resilient line was re-established in 1999 alongside the Control Faecal Egg Count (FEC) line. Selection responses up to 1999/00 in the Elite Resilient-line lambs (relative to the Control line) included a 27% greater post-weaning weight gain (GAIN: Dec. to Apr.), a 0.48 unit reduction in dags, and a 45% reduction in TDR (Dec. to Apr.). A favourable genetic correlation (-0.54) was recorded between TDR and GAIN in lambs, whilst that between TDR and log FEC was -0.17 (not significant). Mean autumn weights in lambs at Ballantrae were 5.8 kg (18%) lower in the Non-Chemical than Conventional treatment groups (P<0.01). Through intense genetic selection, 51% of Elite-line ram lambs are now resilient enough for low-chemical or organic production systems.

Headlines can be Headaches - Scobie DR (Proceedings of the New Zealand Society of Animal Production, 2001)
With some alarm the author read the headline “Scientists Boring” in Rural News in November 1997 (Keating, 1997). Fortunately for the New Zealand Society of Animal Production the page header was “Grassland Conference”. The article, which started “Agricultural scientists are boring the pants off dairy farmers …”, gradually went further down hill explaining that “The [Ruakura Farmers] conference was ‘old and outdated, inflexible and not meeting their needs. Lectures were long boring and often too theoretical’”. The article’s centrepiece claimed “Farmers agreed it was better to have a good presenter talk about somebody else’s research than to have a poor presentation from a good scientist.” The contracted papers that follow this introductory paper indicate steps that members could take to remedy this situation. First and foremost, the reader will note that the papers in this contract are written in layman’s language, outside the guidelines for scientific writing.

How to get an article published in print media - Leggett TW (Proceedings of the New Zealand Society of Animal Production, 2001)
There are levels of exclusivity and there are ways to maximise the impact of your article or idea. I’m not suggesting you attempt to seek money in exchange for your involvement in the article, but you can maximise its impact and uptake by offering a number of different papers their own exclusive angle.

The importance of an accurate estimate of net endogenous loss of magnesium in ruminants - Laporte JA; Bell ST; Sykes AR (Proceedings of the New Zealand Society of Animal Production, 2001)
Attempts to scale up to dairy cattle from a model of magnesium (Mg) metabolism in sheep has shown more rapid reduction in plasma Mg concentration than has been observed in practice when rates of Mg absorption are reduced. Nutrient requirement tables of agriculture research council (1980) provide an estimate for endogenous loss of 3 mg/kg LW/d and, because of the paucity of data, apply this value to sheep and cattle. Such a value represents over 40-50% of the daily requirement for Mg of a typical New Zealand dairy cow even in early lactation. Moreover, the estimate is represented as a constant function of body weight. Net absorption of Mg in ruminants occurs largely in the rumen, but there is recent evidence suggests significant absorption occurs in the large intestine. Therefore, endogenous secretions into the gastrointestinal tract will be available for re-absorption in the large intestine. Under these circumstances it is important for modelling purposes to have an understanding of the true secretion of Mg from which net endogenous Mg losses and, therefore, maintenance needs can be predicted with accuracy. This paper argues from evidence in the literature that net endogenous losses of Mg are unlikely to be a constant. True secretion could be up to 15 times the net endogenous loss because of potentially large exchanges of Mg in different regions of the alimentary tract, which are probably a function of plasma Mg concentration. The case is made a new approach to estimation of maintenance requirement of Mg.

The influence of reproductive status on pituitary gland function in seasonally anoestrous red deer hinds - Fisher MW; McLeod BJ; Meikle LM; Martin SK (Proceedings of the New Zealand Society of Animal Production, 2001)
Changes in pituitary responsiveness to exogenous hypothalamic hormones were assessed during seasonal anoestrous in dry, pregnant and lactating hinds. Of the fifteen adult red deer hinds monitored, five were non-pregnant, five had their calves removed immediately after birth, and five suckled their calves. All hinds were given a single i.v. injection of hypothalamic releasing hormones (5mg each of GnRH, GRF and TRH) on four occasions between Nov/Dec (10 days prior to calving) and March. The pituitary response was determined from changes in plasma concentrations of LH, growth hormone, and prolactin in samples obtained by jugular venepuncture at 0, 15 and 30 min after injection. Reproductive state significantly (P<0.001) affected LH release with a mean response (over all sample dates) of 1.12 ng/ml in dry hinds compared with 0.85 ng/ml in hinds that had their calves removed and 0.60 ng/ml in lactating hinds. Neither growth hormone (average 5.65 ng/ml) nor prolactin (average 33.9 ng/ml) responses were affected by reproductive status.

Intake, live weight and feed-conversion efficiency of lactating Holstein-Friesian dairy cows which differ genetically in live weight - Tolosa MX; Caicedo-Caldas A; Holmes CW; Lopez-Villalobos N (Proceedings of the New Zealand Society of Animal Production, 2001)
The objective of this study was to measure during mid lactation the effect of live weight on the metabolisable energy intake by cows in two lines of Holstein-Friesians selected for heavy or light mature live weight. Yields of milksolids and intakes of dry matter were estimated during two 3-day faeces collection periods. Live weights were measured once in each period. Intakes of pasture dry matter by individual cows were estimated using the alkane technique. Least-square means for live weight, daily yield of milksolids, intakes of dry matter, intakes of metabolisable energy and feed-conversion efficiency for the heavy and the light line were obtained. Linear regression coefficients of metabolisable energy intake on metabolic live weight and yield of milksolids were obtained. Mean values were 15.0 vs. 15.3 kg of dry matter eaten/cow daily, 532 and 488 kg live weight, 1.58 and 1.55 kg milksolids/cow daily, and 108 and 106 g milksolids/kg of dry matter eaten, for the heavy and the light line respectively. The partial regression coefficient of metabolisable energy intake on metabolic live weight was 0.65 MJME/kg LW 0.75 for both lines, similar to commonly reported values. Both lines had similar feed-conversion efficiencies. These data, from 73 grazing cows, generally support other data, and show that live weight does affect maintenance requirements as expected for cows in the heavy and light live weight lines. But they disagree with previous data because the heavy cows did not have higher intakes.

Lactation curves for milk traits, live weight and body condition score for heavy and light Holstein-Friesian cows - Lopez-Villalobos N; Lemus-Ramirez V; Holmes CW; Garrick DJ (Proceedings of the New Zealand Society of Animal Production, 2001)
Two genetic lines of Holstein-Friesian cows divergently selected for heavy and light live weight but with similar genetic merit for farm profitability have been developed at Massey University since 1989. The objective of this experimental project was to evaluate differences in production, fertility and feed efficiency between the two lines when they are managed on grazed pasture and submitted to a seasonal system of reproduction. This paper describe the shapes of the lactation curves for yields of milk, fat and protein, live weigh and body condition score of the two lines using the gamma function. Parameters of the gamma function for each of the traits were estimated for each of 84 cows using daily yields of milk, fat and protein and weekly measurements of live weight and body condition scores recorded during the production season 1998-99. Live weights and body condition scores of mature heavy and light cows at calving were 495 and 436 kg and 4.7 and 4.8 units, respectively. Respective values for first-calving cows were 397 and 352 kg live weight and 4.9 and 4.9 units of body condition score. Peak yields of milk, fat and protein for mature heavy (27.6 litres, 1.30 kg and 0.90 kg) were higher than for mature light (25.6 litres, 1.21 kg and 0.86 kg) cows but differences were not significant. Peaks of yield occurred between 27 and 31 days after calving with no significant differences between lines of cows. There were no significant differences between lines for changes in body condition score and persistency of milk, fat and protein production during lactation of mature cows. Compared to mature cows, first-calving cows had lower peak yields of milk, fat and protein. First-calving light cows were the most persistent and maintained the highest body condition score during lactation. Total predicted yields of milk, fat and protein for mature heavy (4,048 litres, 194 kg and 133 kg) were not significantly different from those for mature light (3,774 litres, 182 kg and 127 kg) cows. These results show that there are no significant differences in the shape of the lactation curve for heavy or light mature cows, but first-calving light cows maintained higher body condition score in late lactation.

Lipolytic response of New Zealand and overseas Holstein-Friesian dairy cows challenged with epinephrine - Kolver ES; Roche JR; de Veth MJ; Mackle TR (Proceedings of the New Zealand Society of Animal Production, 2001)
Sixteen New Zealand Holstein-Friesians (NZ HF) and 15 overseas HF (OS HF) grazing pasture or fed a total mixed ration (TMR) were subjected to an epinephrine challenge during early lactation. A genotype x diet interaction trend (P=0.10) was observed; when grazing, OS HF displayed the greatest glycerol response, with the reverse occurring on TMR. No genotype or diet differences were observed for the glycerol or non-esterified fatty acid response. Dairy cows of both genotypes fed TMR produced a glucose response 31% greater than both genotypes grazing pasture. These preliminary results suggest that genotype x diet-induced differences in the rate of lipolysis may occur in Holstein-Friesians during early lactation. These differences may be a function of small differences in energy balance. Feeding TMR was associated with a greater glucogenic response to epinephrine, which probably resulted from greater hepatic reserves of glycogen or simply a greater energy demand by the mammary gland.

Magnesium endogenous loss as a function of plasma magnesium concentration rather than a constant allows better development of magnesium models in ruminants - Bell ST; Laporte JA; Robson AB; Sykes AR (Proceedings of the New Zealand Society of Animal Production, 2001)
In the course of adapting an existing sheep model of magnesium metabolism for use with lactating dairy cattle it was found that the model failed to predict plasma magnesium concentrations in agreement with experimental data after scaling the model for animal size dependent parameters. An inspection of the model indicated that faecal endogenous Mg loss and Mg absorption from the hindgut were the model components requiring further development. Pooled data from Mg balance experiments were used to investigate the relationship between plasma Mg concentration, net faecal endogenous Mg loss and the apparent availability of magnesium. A mathematical relationship between Mg intake and faecal Mg output is presented. It was derived from the generalised non-linear case to allow for variability in both apparent absorption of Mg and faecal endogenous Mg loss. A balance trial simulation was carried out in which net faecal endogenous Mg was implemented as a linear function of plasma Mg concentration. The results of this simulation were in close agreement with the analysis of pooled balance trial data and suggest that net faecal endogenous Mg loss should be applied to the model as a function of plasma Mg concentration. In fact net faecal endogenous Mg loss is not useful in modelling since it is the net result of a true Mg secretion function being subject to reabsorption in distal regions of the tract. Post rumen magnesium exchanges are examined in the model by implementing net Mg exchanges in the small intestine and hindgut as separate secretion and absorption processes. The difficulties in isolating the true secretion and absorption functions in the hindgut are discussed in conjunction with an initial estimate of these functions. In the modified model the incorporation of a variable endogenous Mg secretion dependent on plasma magnesium concentration provides an additional mechanism for magnesium homeostasis which is sufficient to allow the model to scale between sheep and cattle.

Magnesium supplementation of lactating dairy cows in the summer and autumn - MacDonald KA; Penno JW; Verkerk GA; Jago J; Dow BW (Proceedings of the New Zealand Society of Animal Production, 2001)
A series of three trials were established with 188 lactating dairy cows which were supplemented daily with either 0, 10 or 20 g Magnesium (Mg) during 18 weeks from January to May. Cows in each trial were allocated to treatments randomly in a cross-over design with each treatment lasting 2 weeks. This design was replicated three times during the 18 weeks. There was no treatment effect on serum Mg or milksolids (MS) production, (0.82, 0.82 & 0.83 mmol/l or 0.78, 0.79 & 0.77 kg MS/cow/day for 0, 10 & 20 g Mg, respectively; averaged across all trials) and there were no farmlet-by-treatment interactions. Based on visual assessments of pasture intakes and pasture mineral analysis, mean pasture Mg intakes during all three trials ranged from 23 to 35g Mg/cow/day (SEM 1.14). Urine Mg-creatinine ratio of 50 cows during Trial 3 indicated that the urinary Mg concentration increased linearly with increasing dietary Mg (1.38, 1.87, 2.01 for the 0, 10 and 20 g treatments, respectively; SED 0.175). Trial three results suggest that Mg surplus to requirement was being voided by the cow and that it is unlikely that even at the higher stocking rates, a milk production response to Mg supplementation will occur in the summer/early-autumn period when Mg in diet is >0.18%.

Managing fertility in the New Zealand dairy herd - Holmes CW (Proceedings of the New Zealand Society of Animal Production, 2001)
Effective mating management remains crucially important to pastoral milk production systems in New Zealand (spring calving or autumn calving). The incidence of most diseases has decreased since the 1940s, but infertility, especially the `anoestrous problem`, has increased despite increased use of hormonal treatments and in association with genetic selection for increased yields of milk. The regular need to treat a high proportion of cows with hormones because they are not cycling at the start of mating should be seen as a sign of mismanagement in the system (genetics, health or feeding). `Good herd management` should be used to achieve good fertility with minimal use of hormone treatments; this will include: -good prevention and control of all diseases; all heifers must reach target live weights and puberty at 12 months; all cows must be at BCS 5 at calving, and be fed generously in early lactation; excellent heat detection must be maintained for the entire AI mating period; infertile cows must be culled, and fertility included in the Breeding Worth. These aspects of `good management` must be seen as essential factors in the maintenance of good herd welfare, and in the sustainable production of the high quality, clean and green dairy products required by the world markets. A number of commercial herds are showing that good fertility and good productivity can be achieved with minimum use of hormone treatments, with present-day cows. However, for some strains of cows, good feeding management may be impossible on a diet of grazed pasture.

The media release - Scobie DR (Proceedings of the New Zealand Society of Animal Production, 2001)
Most important in the process of releasing many science stories is the media release. A clear and simple statement of facts in the form of a media release will reduce the errors in the final story. It provides the opportunity for input from scientists, colleagues, collaborators, managers and the all-important investors (who may not want the story or their involvement released). The media release could also be directly circulated to Members of Parliament or Ministers of the Crown, advisory committees and other scientists and non-scientists within the organisation including members of the board of directors. The help of a journalist to translate it into layman’s language will also increase the chances of publication …

Milk yield, prolactin and IGF-1 in cows which calve in Autumn; preliminary report - Wrigley J; Holmes C; Lopez-Villalobos N (Proceedings of the New Zealand Society of Animal Production, 2001)
The objective of this study was to investigate causes of reduced peak milk yield of autumn-calving cows. This experiment is part of a study that is comparing autumn- and spring-calving systems. Two groups of 17 multiparous, Friesian cows that had calved between April 1 and May 6 were fed either ad libitum on grazed pasture (G), or restricted pasture (10kg DM/cow/day) supplemented with maize silage (6kg DM/cow/day) (G + MZ) for a period of 21 days. Milk yield by cows on G increased by 6.2 litres over the 21-day period and was significantly higher (P< 0.01) than the yields of cows on G + MZ. Milk prolactin concentration had no significant association with milk yield. There were higher average plasma concentrations of IGF-1 in the G group (range 104-140ng/mL vs. 95-107ng/mL) that corresponded to higher average milk yields but IGF-1 concentration had no significant association with milk yield. Milk yield and milk prolactin concentration were negatively associated with condition score and plasma IGF-1 concentration was positively associated with condition score.

Modelling the impact of milking frequency on lactation - Vetharaniam I; Davis SR; Soboleva TK; Shorten PR; Wake GC (Proceedings of the New Zealand Society of Animal Production, 2001)
Increasing milking frequency from the usual practice of twice-daily can enhance milk production and, thus, may be profitable in high-intensity dairy production systems. A decrease of milking frequency to once-daily decreases yield but may be used to alleviate nutritional stress, to conserve cow condition, or simply as a lifestyle choice. Published values in the literature indicate that reducing milking frequency from twice daily to once daily decreases yield by 7—34%, and increasing milking frequency from twice daily to thrice daily increases yield by 7—20% (Davis et al., 1999; Stelwagen, 2001). Additionally, milking frequency can influence the rate of decline in post-peak production in cows (Stelwagen, 2001). In order to further understand and quantify the manner in which milking frequency affects lactation, a mechanistic mathematical model of mammary function has been developed (Vetharaniam, Davis, Soboleva, Shorten & Wake, Unpublished), based on mechanisms presented by Davis et al. (1999). As well as allowing analysis of the effect of milking frequency, this model also facilitated the exploration of some of the pathways through which nutrition influences mammary gland development (Davis et al. 2001).

Modelling the impact of nutrition and genotype on lactation - Davis SR; Vetharaniam I; Upsdell M; Kolver ES; Pleasants AB (Proceedings of the New Zealand Society of Animal Production, 2001)
Dairy cows grazed on pasture experience variation in their nutritional status during lactation, as both pasture quality and availability vary seasonally. This has both immediate and long-term consequences on cow performance. Acute effects of nutrition are related to availability of nutrients for milk secretion, and are manifested in day-to-day variation in milk yields. Of further importance are the chronic effects of nutrition, which act on the development of the mammary gland, impacting on the persistency of lactation. Typically, cows in a New Zealand, pasture-grazing environment exhibit a decline in milk yield of around 10% per month, after peak lactation, whereas cows fed a concentrate diet in Northern Hemisphere systems show declines of less than 4%. Post-peak declines in milk yield are associated with a proportional and permanent decline in the number of secretory cells in the udder, and this decline is modulated by nutrition (Davis et al., 2000). Quantifying the milk-yield response of a cow to different nutritional regimes is useful from a breeding and selection point of view, but on its own does not give insight into which pathways are likely to be affected by nutrition, nor does it explain the origin of differences in responses between cows. To this end, mechanistic mathematical models that reflect the underlying biology of the udder are particularly useful.

Monitoring adrenal activity in dairy cows under various feeding regimens using faecal glucocorticoid metabolites - Morrow CJ; Kolver ES; MacDonald KA; Verkerk GA; Matthews LR (Proceedings of the New Zealand Society of Animal Production, 2001)
Adrenal activity in cattle can be measured by changes in plasma glucocorticoid concentrations. Cows treated with synthetic adrenocorticotrophic hormone (ACTH) to stimulate the adrenal cortex exhibited elevated plasma cortisol concentrations for 4-5h. Concentrations of faecal glucocorticoid metabolites (FGM) peaked between 8-9.5h after ACTH treatment, 2.5 fold higher than basal (P<0.05) and remained elevated for 13h (range, 11.1-16.1h). Faecal glucocorticoid concentrations were monitored in two strains of Holstein Friesian (HF) dairy cows farmed in New Zealand under two systems: NZ pastoral and North American concentrate-based. The overseas (OS) and New Zealand (NZ) HF were fed a pasture-based diet (Grass) or a total mixed ration (TMR) throughout lactation. Faecal samples were collected on four occasions during lactation. Faecal glucocorticoid concentrations of the cows fed Grass were consistently higher (P<0.05) than cows fed TMR. There was also a significant genotype effect; FGM concentrations of the NZ HF cows were higher than OS HF cows (P<0.05). In a separate study, no obvious trends were evident in FGM in NZ HF grazing pasture at three stocking rates (2.2, 3.2, 4.3 cows per hectare). Measuring FGM can be used to monitor acute adrenal activity in cows, but is more difficult to interpret as a measure of chronic stress.

Nutraceuticals - Keeley R (Proceedings of the New Zealand Society of Animal Production, 2001)
Nutraceuticals can be defined as “products isolated or purified from foods and generally sold in medicinal forms not usually associated with food, and have demonstrated physiological benefits or provides protection against chronic disease”.

Nutrition and lameness in pasture-fed dairy cattle - Westwood CT; Lean IJ (Proceedings of the New Zealand Society of Animal Production, 2001)
This review examines the potential for nutritional factors to contribute to the high incidence of foot lameness in New Zealand pasture-fed dairy cattle. Spring and autumn temperate pastures are highly digestible, contain high concentrations of rumen degradable protein and the effectiveness of neutral detergent fibre (NDF) may be too low to support optimum rumen function. Risk of laminitis and lameness increases with chronic ruminal acidosis and there is evidence for sub-optimal rumen pH in New Zealand cows. Inadequate uptake of trace elements and minerals may compromise hoof health, and there is evidence for lameness associated with the ingestion of high concentrations of anti-nutritional compounds. The clinical examination of lameness in pasture-fed cows must incorporate an investigation of the nutritional status of the cow in addition to environmental, management and animal factors.

Opportunities for enhancing the delivery of novel forage attributes - Cosgrove GP; Parsons AJ; Marotti DM; Rutter SM; Chapman DF (Proceedings of the New Zealand Society of Animal Production, 2001)
Allocating spatially separated forage choices to grazing animals overcomes constraints inherent in mixed pastures and sustainably delivers the required diet composition, satisfies their desire for mixed diets, and so offers a simple way to enhance the delivery of the benefits of current and novel forage attributes. Sheep offered grass and clover in this way increased daily dry matter intake by 265 g/day (25%, P<0.05) compared with conventional pasture and sustained 60-70% clover in their diet. Milk production by cows was boosted by 11% (2.4 kg/cow/day, P<0.01).

Optimal utilization of genetic resources in aquaculture - Amer PR; Jopson NB; Dodds KG; Symonds JE; Hills J (Proceedings of the New Zealand Society of Animal Production, 2001)
This paper uses a vertically integrated salmon farming company as a case study to describe how quantitative genetics and decision support optimisation tools have been used in an aquaculture breeding programme. The complex tasks of maximising genetic progress while managing genetic diversity and avoiding inbreeding are considered at two levels. The first level relates to the management of a nucleus breeding structure for which long term genetic progress and management of genetic diversity are the primary objectives. The second level relates to the tactical selection among available broodstock candidates and their mating to avoid inbreeding. The importance of both effective data management systems and practical implementation of theoretical genetic principles is emphasised.

Possums as vectors of Tb in livestock - Coleman JD (Proceedings of the New Zealand Society of Animal Production, 2001)
Bovine tuberculosis (Tb) is the most important disease of livestock in New Zealand, and it occurs in cattle and deer herds at relatively high incidences by international standards. Brushtail possums are the major wildlife vector and maintenance host of Tb in New Zealand, and their infection is the single greatest barrier to the eradication of Tb from New Zealand livestock. The control of infected populations of possums underpins attempts to eliminate the disease from livestock. Possum populations infected with Tb occupy about 24% of New Zealand, which is also where about 75% of the reactor herds and Tb-infected cattle occur. Possums with Tb often exhibit lesions in their lungs and external lymph nodes and infection in these sites appears to be involved in the transmission of the disease to other possums. The mode of transmission of Tb from possums to livestock is unproven, but it is thought to occur when inquisitive stock encounter dying possums.

Postpartum anoestrous interval and metabolic changes in heifers supplemented with pasture prepartum - Chagas LM; Morgan SR; Gore PJS; Clark BA; Verkerk GA (Proceedings of the New Zealand Society of Animal Production, 2001)
The aim of this study was to determine whether supplementation with pasture from 6 weeks before calving would alter the postpartum anoestrous interval (PPAI) in heifers calving with low body condition score (BCS). Metabolic hormones and metabolites were measured during the pre- and postpartum period. Forty Friesian heifers were managed during the last five months of gestation to achieve a BCS (1-10) of 4.0 (restricted; R; n=27) or 5.0 (fully fed; FF; n=13) by 6 weeks prepartum. One group with low BCS then received pasture ad libitum until calving (restricted + fully fed; R+FF; n=12). Live weight (LW) and BCS were assessed weekly. Blood samples were collected weekly from 10 weeks prepartum to 10 weeks postpartum to measure glucose, urea, non-esterified fatty acids (NEFA), betahydroxybutyrate (BOH) and cholesterol content. The patterns of metabolites measured differed between groups at different times, future work to investigate the relationship these profiles and PPAI would be of value. The percentage of cows cycling as measured by an elevated milk progesterone concentration was 69%, 75% and 8% for FF, R+FF and R groups, respectively. Fully feeding heifers, with low condition score, 6 weeks before calving decreased PPAI when compared to heifers receiving restricted feeding.

Potential benefits from new reproductive technologies in commercial dairy herds; a case study simulation - Smeaton DC; Vivanco HW (Proceedings of the New Zealand Society of Animal Production, 2001)
New reproductive technologies may provide the possibility to derive the egg component of embryos for dairy cow replacements from only an elite proportion of the dairy herd, or from heifers or calves, thereby creating opportunities for greater genetic gain. Using modelling, four possible selection strategies in two case study herds were compared over 10 years at annual replacement rates of 15, 20 and 25%. In the different strategies, replacement calves were bred from: (1) AB bull + all herd cows, `status quo` vs (2) AB bull + only the top 25% of herd cows vs (3) AB bull + the top 100% of maiden heifers vs (4) AB bull + the top 100% of heifer calves. Assumptions used included (1) an average bull breeding worth (BW) of $135, gaining by $5 per year. (2) A `high BW herd` average BW of $62 (almost in the top 10% of all New Zealand herds). (3) A `low BW herd` average BW of $32 (nearly in the bottom 10%). The model predicted that rate of herd genetic gain increased with replacement rate. The low BW herd gained more than the high BW herd using any of the strategies because it started from a lower base. The BW of the 2 herds converged over 10 years and this effect increased with selection pressure. After 10 years, BWs of 150 and 149 were predicted for the high and low BW herds respectively by using eggs from calves as in Strategy 4 above. This compared with Strategy 1 where herd BWs at year 10 were 130 and 120 respectively.

Potential transmission routes of rabbit haemorrhagic disease: Consequences for epidemiology of RHD in wild rabbits - Parkes JP; Norbury GL; Heyward RP; Heath ACG (Proceedings of the New Zealand Society of Animal Production, 2001)
Rabbit haemorrhagic disease (RHD) was released in New Zealand in the spring of 1997 and has subsequently spread naturally and with the assistance of people to most, if not all, rabbit populations in the country (Parkes et al., 2001). The disease and its impact on rabbit numbers have been described for the initial epidemics in Otago rabbit populations (O’Keefe et al., 1999), in ongoing cross-sectional studies at 10 sites in Canterbury and Otago (Parkes et al., 2001), and in a single longitudinal study in the Manawatu (Henning et al., 2000). In this paper we wish to discuss alternative ways the RHD virus (RHDV) might be transmitted to rabbits, report on the evidence from field and pen trials on various transmission routes, and speculate on the possible routes that fit the observed epidemiological data from our study sites in Otago and Canterbury.

Prediction of ruminal pH of dairy cows fed pasture - de Veth MJ; Kolver ES (Proceedings of the New Zealand Society of Animal Production, 2001)
Rumen pH as low as 5.6 has been reported in cows fed highly digestible pasture, however, incidences of sub-acute acidosis have not been well documented and there are no easy or reliable means for farmers to measure ruminal pH. This study collated animal and dietary parameters (81 treatment means), from 20 studies of lactating dairy cows fed pasture, to evaluate the relationship between ruminal pH and animal parameters, and identify suitable predictors of ruminal pH. Mean ruminal pH (5.6-6.7) was negatively correlated (P<0.05) with total volatile fatty acid concentration, milk yield, microbial N flow from the rumen, milk protein yield, milk fat yield, total non-structural carbohydrate content and acid detergent fibre content of the diet. No single dietary parameter, or group of parameters, was able to adequately predict ruminal pH. The increase in microbial nitrogen flow, milk, and milk fat production as ruminal pH decreased below 6.2 suggested that the performance of cows fed high quality pasture was not limited when mean ruminal pH decreased to 5.8. This implies that dairy cows fed pasture can tolerate a lower ruminal pH before sub-acute acidosis occurs than when forage-concentrate diets are fed.

Presidential Address 2000: Animal products contribution to New Zealand's wealth - Bray AR (Proceedings of the New Zealand Society of Animal Production, 2001)
The 60th anniversary of the New Zealand Society of Animal Production is an appropriate occasion on which to acknowledge the massive contribution that animal products have made to the New Zealand economy. Maori used products from kiore and dogs as well as wildlife and fish. The first Europeans started with whaling and sealing, then moved to wool production before freezers on ships opened up world meat markets. More recently dairying and fishing have boomed and chicken, meat and egg, pork and deer industries have arisen. Add goat, ostrich, mussels, possums etc and you have a long, varied list of species and products. However it is the products from grazing sheep and cattle that have provided the bulk of New Zealand’s export earnings over the last one hundred and fifty years. They continue to dominate to this day …

Progress in controlling Bovine Tuberculosis in New Zealand - Livingstone P (Proceedings of the New Zealand Society of Animal Production, 2001)
Bovine tuberculosis (Tb) is the greatest disease problem facing the New Zealand cattle and deer industries. During the 1999/00 financial year, 1,212 (1.67%) cattle and deer herds were infected at some point, eight times the international accepted level for freedom from infection. The source of infection for cattle and deer herds is predominantly wild animals, particularly possums and in some parts of the country, ferrets. Areas where wild animals act as a source of Tb infection for cattle and farmed deer are classified as Vector Risk Areas (VRAs). Currently 33% of New Zealand’s land area is classified as VRA. Reducing the density of Tb vectors in VRAs, to minimise contact with cattle and farmed deer, is therefore a core requirement for controlling bovine tuberculosis in New Zealand …

Is Public Relations just Spin Doctoring or is it Reputational Risk Management? - Fernandez F (Proceedings of the New Zealand Society of Animal Production, 2001)
Public Relations has been described as ‘making the crap credible’. Many would argue that promoting biotechnology and genetic engineering research in today’s political environment definitely falls into this category. Indeed there may be a very thin line between promoting or defending such research. While such work may be labelled as ‘public relations’ by the traditionals, or ‘spin doctoring’ by the more cynical, a more valid and correct label for it would be ‘reputational risk management’.

Radio Interviews - Wynn-Harris S (Proceedings of the New Zealand Society of Animal Production, 2001)
The author is not a trained journalist, merely a farmer given the opportunity to get behind a microphone twice a week and produce a live show that runs an hour over lunchtime each Tuesday and Thursday, which is then replayed the following morning between 6 to 7am. The show is called ‘The Cockies Hour’ and is on Central FM, which broadcasts from Woodville to Hastings. The station is a commercial station, which has a few constraints and differences from a non-commercial station such as the state broadcaster, National Radio. However, both have many similarities.

Relationship between bulk milk urea nitrogen and reproductive performance of New Zealand dairy herds - Smith JF; Beaumont S; Hagemann L; McDonald RM; Peterson AJ; Xu ZZ; Duganzich DM (Proceedings of the New Zealand Society of Animal Production, 2001)
New Zealand dairy cows grazing lush spring pasture have relatively high plasma urea nitrogen levels as a consequence of the high soluble crude protein content of this rapidly growing pasture. The elevated plasma urea levels have been implicated as a cause of poor reproductive performance in dairy herds. The aim of this trial was to determine if the bulk milk urea nitrogen levels (BMUNs) collected during the period from calving and through mating were related to the reproductive performance of the herds. Bulk milk samples were collected twice a week from 127 farms during the spring of 1998. The farms were suppliers of the NZ Dairy Group and Kiwi co-operatives. Reproductive performance data was collected from all herds. BMUNs were determined spectrophotomically using Sigma blood urea nitrogen kits. The twice-weekly BMUNs were averaged for each farm and these weekly mean values were centred on the nominated week of mating (W=+1) for the individual farms. There were significant among-farm differences in BMUNs with individual weekly farm values ranging from 5.4 to 26.8 (mg/dl) and the mean (W-3 to W+5) value for farms ranging from 9.6 to 18.8 (mg/dl). There were significant between farm differences in reproductive performance. The percentage of cows submitted for AI in first 3 weeks of mating (%SR21) ranged from 29.9 to 95.3%. The percentage of SR21 cows conceiving to that AI (%Preg1) ranged from 39 to 98.6% and the percentage of all cows in the herd pregnant by the end of mating (%Pregall) from 44.9 to 98.4%. There was some indication of a relationship between reproductive performance and BMUNs in that the change in BMUN level from W-3 to W+5 was significantly correlated within geographic zones with %SR21 and %Pregall, correlation coefficients being 0.36 (P=0.013) and 0.37 (P=0.010) respectively. The corresponding correlation for %Preg1 was only 0.21(P = 0.15). Thus farms for which BMUNs rose over the period W-3 to W+5 had higher reproductive performance than those in the same zone, which showed a fall. However, this accounted for very little of the overall variability. Farms were ranked on their reproductive performance and the average weekly BMUNs for the farms in each quartile calculated. There was no difference in the pattern of BMUNs for the different quartiles of each reproductive parameter. Thus, the measurement of BMUNs would appear to be of little value as an indicator or predictor of reproductive performance.

Relationships between, milk production, nutrition and reproduction in benchmark herds - Smith JF; Verkerk GA; Clark BA; McKay BJ; Duganzich DM (Proceedings of the New Zealand Society of Animal Production, 2001)
Inter-relationships between nutrition, milk production and reproduction in dairy cows were investigated in dairy herds with previous high reproductive performance. Ten herds were selected as `benchmark` farms from one area of the Waikato. Pasture and supplement intakes, and milk production were monitored on a herd basis. Bulk milk samples were taken weekly from calving through to the first three weeks of mating and assayed for levels of progesterone, urea nitrogen and b-hydroxybutyrate (BOH). Pre-mating oestrus, mating (AI) and pregnancy data were recorded. All data was expressed in relation to the planned date of mating (PSM) for each farm. Significant between farm differences were detected in all the reproductive parameters but there was no effect of supplement feeding. The mean proportion of cows cycling at PSM was 65.6 ± 3.3% (range 50.5 to 81%).The mean proportion of cows pregnant to AI at PSM + 3 weeks was 51.3 ± 2.1% (range 43 to 61.5%); at PSM + 6 weeks the mean was 74.5 ± 3.3% (61 to 89.5%); at PSM + 9 weeks it was 84.7 ± 2.2% (74.9 to 91.6%) and at PSM + 12 weeks it was 91.3 ± 1.2% (85.6 to 95.4%). Bulk milk progesterone rose linearly from a mean of 0.5 ng/ml at 8 weeks before PSM to 5.0 ng/ml at PSM and to 6.0 ng/ml three weeks later. The difference between farms at PSM ranged from (2.1 to 7.1 ng/ml). While the pattern of increase in bulk milk progesterone tended to mimic the overall pattern of oestrus activity, there was no relationship in the ranking of farms for these parameters at any time. Bulk milk BOH showed no consistent pattern over the period of measurement and levels ranged between farms in any one week from 0.01 to 0.05 mM. Bulk milk urea nitrogen concentration also showed little change on average (7.25 mM) over the pre-mating and mating periods. The significant between-farm differences in these bulk milk parameters did not appear to be related to reproductive performance. Metabolic indicators measured in bulk milk samples appear of little value for predicting reproductive performance at herd level.

Reproductive physiology and management of high-yielding dairy cattle - Lucy MC (Proceedings of the New Zealand Society of Animal Production, 2001)
The future efficiency of the dairy industry will undoubtedly be affected by the decline in fertility and reproductive efficiency in modern dairy cows. The cause of the declining fertility is probably a combination of genetic, physiological and management factors that have an additive effect on reproductive efficiency. Milk production per cow has increased and is one factor that is contributing to the problem. In addition to milk production, however, many other equally important factors may be involved. For example, the reproductive physiology of dairy cattle has changed in response to genetic selection for milk production and these changes may require different management strategies. Compared to traditional dairy cows, modern dairy cows have longer intervals to first ovulation, a higher incidence of anoestrus, abnormal luteal phases, lower blood progesterone concentrations, and greater embryonic loss. Reproductive decline can be reversed in dairy cows but a collective effort that includes more intense reproductive management, genetic selection for improved fertility, and new scientific discoveries will be necessary before the problem can be solved.

Resynchronising returns-to-service in anoestrous cows in Victorian dairy herds - Eagles VE; Malmo J; Macmillan KL (Proceedings of the New Zealand Society of Animal Production, 2001)
Many cows treated for anovulatory anoestrus in Victorian herds which fail to conceive to first insemination also fail to return-to-service 18 to 24 days later. A trial in 16 herds in the Maffra district determined whether treatments to re-synchronise returns-to-service could also increase submission rates for a second insemination in these cows. The 810 Holstein cows initially treated for anovulatory anoestrus provided 691 for inclusion in the study. A previously used CIDRTM device was re-inserted 12 to 14 days after first insemination with injected oestradiol benzoate (1mg ODB), and was removed 7 days later. Some cows received no further treatment (Group 1; n=357); the remainder were each injected with 0.5mg ODB 24h after device removal (Group 2; n=334). Conception rates were similar for the two Groups (1st insem: 29% vs. 32%; 2nd insem: 44.5% vs. 46.4%). The higher submission rate for synchronised second inseminations in Group 2 (40% vs. 65%; P<0.01) meant that the median interval from first insemination to conception was reduced from 42 days (Group 1) to 23 days (Group 2 ; P<0.01); pregnancy rates after 6 weeks of AI were increased from 51.5% to 59.6%, respectively (P<0.01). The injection of ODB given after device removal for resynchrony improved the efficacy of treating anoestrous cows in these Victorian herds.

Scientists and the media: Attracting and avoiding attention - Johnstone LA (Proceedings of the New Zealand Society of Animal Production, 2001)
“The public’s right to know and the scientist’s duty to inform are essential in a civilised democracy” – a pompous statement made by Johnstone (2000). The author suspects that, generally speaking, there are two common views among scientists about the media. Most scientists actively dislike the media; some merely mistrust them. Despite that, the author continues to encourage scientists to overcome those views, jump in to the media bath, and talk about their work, their worries, and their hopes. If they fail to do that, others will decide what people should be told about scientific matters.

The search for quantitative trait loci affecting wool colour - McKenzie GW; Maher AP; Dodds KG; Beattie AE; Henry HM; Hickford JGH; Montgomery GW (Proceedings of the New Zealand Society of Animal Production, 2001)
Farmers have been attempting to breed whiter wool for some time using quantitative and subjective genetic selection based on phenotypic traits. The improvement of wool colour using this form of selection has achieved limited success. The advent of DNA marker maps has introduced the possibility of more directly relating phenotypic and genetic variation. Work presented here has identified a total of ten potential quantitative trait loci (QTL) that are significant at the suggestive level, and one additional QTL that approached this significance threshold that influence wool colour. There have been five putative QTL identified for base colour or challenge colour brightness. Two QTL affecting challenge colour yellowness was identified, while three QTL identified were linked to predictive colour variation. An additional QTL that affected predictive colour has also been mapped to a non-specific location on chromosome 24. Several further key areas of research need to be addressed before the DNA markers can be developed for use in the improvement of wool colour.

Simulated impacts of new reproductive technologies on the productivity of beef production systems - Smeaton DC (Proceedings of the New Zealand Society of Animal Production, 2001)
A computer simulation model was developed to explore how new reproductive technologies could improve beef productivity through embryo transfer (ET), sex ratio control and use of small cow breeds pregnant to `high growth rate` calf genetics. Assumptions were made about conception rates, embryo losses, sex ratios, cow and calf survival, animal weights, and the feed requirements of small and large cows rearing large calves. A range of pregnancy rates from ET (40 to 67%) were assumed compared to natural mating (67%) and it was also assumed that a small cow breed, such as a Jersey, could rear calves to similar weights of those from Hereford x Friesian (H x F) cows. Cow efficiency values were derived as the estimated intake of metabolisable energy by the cow plus calf unit per year per kg of calf weaning weight. The model was based on averages with variance information from fieldwork used for @Risk analyses. In the model, H x F cows subjected to the new technologies such as ET (involving synchronised calving) and sex ratio control were up to 9% more efficient than the `status quo` mating system. Using a small cow, however, gave gains in efficiency of up to 20%. These benefits were highly dependent on the assumptions used, in particular ET pregnancy rate and cow and calf losses at calving, all of which, singly or together, above threshold values, could destroy the gains or even create losses in efficiency.

Tasmanian grass grub - a significant threat to pastoral farming in dryland regions - Slay MWA; Fisher MW (Proceedings of the New Zealand Society of Animal Production, 2001)
Tasmanian grass grub, first recorded in Canterbury in 1920, is now well established in several areas of New Zealand. The adult beetles fly in January and lay their eggs in the soil after mating. After hatching, the larvae live in the soil and construct vertical tunnels from which they emerge at night to feed on and denude pasture plants. The effects of this pest on pasture were estimated by measuring pasture with larval densities ranging from 21-574 m². Larval infestation significantly reduced pasture mass in a linear fashion by around 5% per 100 larvae. For example, at one site from July to September, pasture mass Y = -0.816X + 1852, R2 = 0.3; where Y = pasture mass (kg DM per ha) and X = larvae per m². Losses in stock carrying capacities have been estimated to vary between 0.5 and 5 stock units per hectare depending on the farm carrying capacity and larval damage to pasture, resulting in losses of up to $315 per hectare.

Toward a predictive model of supplementary feeding response from grazing dairy cows - Penno JW; MacDonald KA; Holmes CW (Proceedings of the New Zealand Society of Animal Production, 2001)
Many experiments have measured the responses of grazing dairy cows to supplementary feeds, but few have studied the reasons for the large differences in responses between experiments. Data derived from two trials, in which supplementary feeds of either maize grain or a nutritionally balancing ration were offered to cows in early, mid, and late lactation in each of spring, summer, autumn and winter, were used to calculate the marginal milksolids responses to supplements. The data set created was subject to multiple regression analysis in an attempt to quantify the effect of the different variables on the magnitude of the response to supplementary feeds. The factor that was of greatest importance was the relative feed deficit (RFD) of the cows measured by the reduction in milksolids yield (kg MS/cow/day) of the respective control groups that had occurred when the restricted feeding treatments had been imposed. Total marginal milksolids responses were greatest when severe feed restrictions, relative to current feed demand, resulted in large reductions in milksolids yield of the control groups. Total marginal milksolids response increased (P<0.01) by 0.9g MS/MJME offered as supplement per 0.1 kg MS/cow/day RFD. Total marginal milksolids responses also declined (P<0.01) by 0.2 g MS/MJME offered as supplement as pasture allowance increased by 10 MJME/cow/day.

Will the big birds fly? - Thompson KF; Binks S (Proceedings of the New Zealand Society of Animal Production, 2001)
Modern ostrich farming in New Zealand commenced in 1994 with importation of eggs. In 1997 the first processing of ostrich meat for the domestic market occurred. By 1999 there were estimated to be 2500 breeding hens, 12,000 chicks and 10,000 rising 1-year-old birds. The current domestic market for ostrich meat is about 100 tonne annually and there has been an increase of 70% in the last 12 months. About 4000 yearling birds provide meat for the domestic market. Export of ostrich to Europe commenced in 2000. At current prices the limiting constraint is achieving 15 slaughter birds per hen each year. Slaughter birds need to be over 95 kg live weight. Quality of hen nutrition is considered a critical factor influencing embryonic mortality and chick survival. The target rate is being achieved by some farmers, but for this to be an industry average, further developments in breeding hen nutrition and young chick survival will be required.

y-glutamyl transpeptidase and amino acid transport for milk protein production in vivo - Johnston SL; Roy NC; Davis SR; Tweedie JW; Kitson KE; Lee J (Proceedings of the New Zealand Society of Animal Production, 2001)
Activity of the enzyme g-glutamyl transpeptidase (g-GT) (EC 2.3.2.2) a putative facilitator of amino acid (AA) transport in the mammary gland, increases before lactation and decreases at weaning, suggesting a role in AA transport for milk protein synthesis. The effect of g-GT inhibition by acivicin and supply of cyst(e)ine from N-acetylcysteine (NAC) on mammary AA uptake and milk production was studied in lactating goats. NAC increased (P<0.05) arterial supply of some AA but did not increase arterio-venous difference as a percentage of arterial supply (extraction %) and did not alter milk protein yield. Acivicin decreased (P<0.05) milk protein yield but this effect was not found when NAC was administered in combination with acivicin. This indicates that NAC, by indirectly enhancing intracellular cysteine, countered the effect of acivicin inhibition, suggesting a role for g-GT in supply of cysteine for milk protein synthesis.

Analysis of milk constituents by near infrared and visible light - Whyte DS; Kunnemeyer R; Claycomb RW (Proceedings of the New Zealand Society of Animal Production, 2000)
Herd testing, in which individual cow’s production performance is measured, is infrequently carried out in New Zealand with at least a month between tests. A composite sample is collected from each cow and is analysed for fat, protein, and somatic cell count (SCC). The process is time consuming, and provides only a snapshot of these components. To create a more frequent, automated, on-farm system, sensors need to be developed that measure fat, protein, SCC, and other milk components inexpensively and easily. One potential measurement method which could be used in these devices is visible to near infrared (NIR) spectroscopy. The industry currently uses a range of sophisticated machines (Fossomatic, Foss, Hedehusene Denmark) for the determination of milk constituents. These machines homogenise milk and use infrared (IR) spectroscopy in the wavelength range 3500-9600 nm to determine fat, protein, and lactose concentrations. SCC is determined by an integrated flow cytometer. The NIR region (1000-2500 nm) has also been successfully used to determine constituents of milk and milk products (Rudzik & Wüst, 1998). Any inexpensive, on-line sensor based on NIR spectroscopy should function without the requirement for homogenisation and use low-cost silicon photodetectors, which are sensitive from 400-1100 nm.

Behaviour response of calves to amputation dehorning with or without local anaesthesia - Stafford KJ; Mellor DJ; Ward RN; Cann B (Proceedings of the New Zealand Society of Animal Production, 2000)
This study tested the hypothesis that the expression of some specific behaviours of calves following amputation dehorning is modified by use of local anaesthesia such that their behaviour is similar to calves which were not dehorned, during the period of action of local anaesthesia. The hypothesis was not supported and the behaviour of calves given local anaesthesia was similar to animals dehorned without anaesthesia during the two hours after amputation dehorning and not similar toanimals which were not dehorned. It is possible that the behaviours which were monitored (feeding, rumination, grooming,lying down, ear-flicks, head-shakes, tail-shakes) were not relevant to the pain experienced by calves after dehorning.However, there were significant differences between the behaviour of control animals and those that were dehorned. Thephysical change caused by dehorning and the bleeding that occur afterwards may influence these behaviours so that the additional effect of the pain caused by amputation does not modify it further.

The benefits of sheep recording schemes for genetic research - Clarke JN; Garrick DJ (Proceedings of the New Zealand Society of Animal Production, 2000)
Recording schemes designed to provide genetic evaluations at the individual animal level contain basic pedigree and production records fundamental to genetic research. Accessibility, accuracy and consistency of their information and the flexibility of their database design to incorporate new indicator traits with prospects of providing a more accurate or more cost-effective identification of animals able to leave superior progeny influence their value to research. Much research is also likely to benefit from inclusion or access to industry data on animal products and their processing performance beyond the farm gate. Industry-wide evaluations of animals in different flocks can also identify useful contrasting animals for this research as well as for commercial exploitation. Examples of research using industry data from recording schemes are presented to demonstrate these features. They include estimates of non-genetic influences on animal performance, on methods of adjusting for their effects, estimates of phenotypic and genetic parameters, of genetic group and gene effects, of the effects of selection and culling and their impact on selection and crossbreeding strategies. Research embracing new molecular technologies is also discussed. Research of this sort can have high extension impact, especially that geared to early incorporation of results into the animal evaluation procedures of the scheme itself.

Cattle behaviour: Comparison of measures of temperament in beef cattle - Fisher AD; Morris CA; Matthews LR (Proceedings of the New Zealand Society of Animal Production, 2000)
The aim of the study was to evaluate three measures of cattle temperament which incorporate tests of human presence and separation from herdmates. The study utilised 134 heifers and 137 steers which were grazed as two single-sex herds. The cattle were rising 2-year-old, and were of either 3/4 Limousin x 1/4 Jersey or 3/4 Jersey x 1/4 Limousin breed-type. Flight distance was measured for each animal in the paddock and in the handling yards. A test of animal sociability measured the time taken by an animal to move to a pen containing herdmates. Each test was conducted on three occasions at intervals of one month. In contrast to the other two measurements, yard flight distance was highly repeatable with a repeatability coefficient of 0.51 between separate tests for heifers and steers. The repeatabilities for the paddock flight distance and sociability test were 0.36 and 0.34, respectively. In conclusion, the yard flight distance test represented an effective and repeatable measure of cattle response to humans.

Cloning and characterization of the bovine myostatin promoter - Sharma M; Martin JK; Jeanplong F; Thomas M; Spiller MR; Bass JJ; Kambadur R (Proceedings of the New Zealand Society of Animal Production, 2000)
Myostatin a TGF beta superfamily member has been shown to be present in high levels in the myogenic precursor cells of dermomyotome and in the adult muscle fiber. To identify cis-acting DNA elements involved in myostatin gene expression, we have isolated and sequenced several kilobases of the bovine myostatin promoter region. Sequence analysis of the 1.6 kb immediate upstream region of bovine myostatin revealed several muscle specific transcription factor binding sites such as E-boxes and an MEF2 binding site in this region.

A comparison New Zealand and overseas Holstein Friesian heifers - Kolver ES; Napper AR; Copeman PJA; Muller LD (Proceedings of the New Zealand Society of Animal Production, 2000)
The performance of overseas (OS) and New Zealand (NZ) Holstein Friesian (HF) dairy heifers was compared when fed an all-pasture diet (Grass) or a total mixed ration (TMR) throughout lactation. The four treatments were NZ Grass (n=14); OS Grass (n=9); NZ TMR (n=15); and OS TMR (n=10). Compared with NZ HF, OS HF had a higher live weight and produced more milk, but milksolids yield, efficiency of milksolids production, and persistency of lactation were not different. Compared with HF fed Grass, HF fed TMR produced more milk and milksolids, were more efficient, had a greater persistency of lactation, and ended lactation with a greater body weight. The OS HF genotype was unable to maintain acceptable body condition and live weight on an all-grass diet. This raises serious questions regarding the sustainability and suitability of these genetics for seasonal all-pasture dairying systems.

Comparison of selected reproductive characteristics in Overseas and New Zealand Holstein-Friesian cows grazing pasture or fed a total mixed ration - Verkerk GA; Morgan S; Kolver ES (Proceedings of the New Zealand Society of Animal Production, 2000)
Lactating overseas and NZ-derived Holstein-Friesian cows were fed either pasture or total mixed ration (NZGrass, n=14; NZ TMR, n=14; OSGrass, n=12; OS TMR, n=13). For cows ovulating before breeding began, mean postpartum anoestrous intervals (PPAI) were 39±6, 29±4, 27±6 and 23±2 d, respectively. Of 13 cows with PPAI 43d, four were NZGrass (P<0.02). Of seven with PPAI >43d, four were NZGrass (P<0.05). Growth of the first dominant follicle and corpus luteum through time, and day of emergence of the second follicle wave, measured by transrectal ultrasonography, did not differ between treatment groups. Feeding system affected mean plasma progesterone concentration at emergence of the second follicle wave and number of subordinate follicles recorded during the first follicle wave (4.5 ± 0.4 and 6.1 ± 0.5 ng/ml, P<0.02; 6.2 ± 0.6 and 4.1 ± 0.7 follicles/d, P<0.05; for grass and TMR, respectively). In summary, both genotype and feed system affected length of PPAI, while feed system influenced aspects of peripheral hormone profiles.

Dairy farmer perceptions of the industry's 'clean and green' image - Billones R; Parker WJ; Kuiper D (Proceedings of the New Zealand Society of Animal Production, 2000)
The purpose of this research was to quantify how dairy farmers believed their practices contributed to (or harmed) NewZealand’s “clean and green” image. Dairy farmers (n=350) from eight regions of New Zealand were surveyed by mail.The majority of respondents (n=218) were mainly male (88%), older than 40 years (65%) and owner-operators (45%) orsharemilkers (31%). Some 81% thought New Zealand dairy farming deserved its “clean and green” image, 90% said thisimproved the marketing of New Zealand dairy products internationally, and 72% believed consumer perceptions of farmingpractices did affect their purchase decisions. The farming practices most strongly associated with a negative impact on the“clean and green” image of dairying were: cows in muddy paddocks (81% farmers), induction (71%), bobby calves by theroadside (62%) and tail docking (59%). Enhancers of the image were pasture grazing by cows (87%) and being outdoorsyear round (62%). The majority of farmers believed larger herds (80%), bloat drenching (79%), dehorning (65%), intensivefertiliser use (65%), effluent disposal (58%) and use of antibiotics (53%) to have no effect on the “clean and green” image.Concerns were expressed that a small group of farmers with poor management practice could seriously affect the industry’s image.

Dairy farming, nitrogen losses and nitrate-sensitive areas - Ledgard SF; de Klein CAM; Crush JR; Thorrold BS (Proceedings of the New Zealand Society of Animal Production, 2000)
Dairy farms exhibit large nitrogen (N) fluxes throughout the soil/plant/animal system. These fluxes increase with increasing N inputs and farming intensity, and can lead to significant N losses into the environment. Under New Zealand grazed pastoral systems, the N losses occur predominantly from animal urine. Nitrogen can impact on water quality for human consumption or for aesthetics, recreational use and fisheries via enhanced aquatic plant or algae growth. In this paper, N flows in dairy farms in New Zealand are compared with those in the European Union (EU), where dairy farming is generally more intensive. In the EU, legislation is being used to reduce N losses from intensive dairy farming in nitrate sensitive areas through defined maximum rates of manure application. Progressive reduction in these rates will potentially reduce stocking rates on intensive EU farms such as in the Netherlands, where taxation of farm N surpluses is also used as a deterrent. New Zealand has a lower average farming intensity and lower N losses to the environment than in intensive EU farms. However, farmlet systems research has shown that high N inputs of c. 400 kg N/ha/yr can increase nitrate-N concentration in groundwater by up to twice the recommended maximum for drinking water. In nitrate sensitive areas, such as around Lake Taupo, it is desirable to minimise nitrate leaching and the associated lateral movement to surface water bodies. A range of on-farm options are discussed including limiting external N inputs, increasing N use efficiency via lower protein feed sources, reducing farm dairy effluent N losses, and avoiding direct deposition of excreta to land in autumn/winter using grazing-off or feed-pad systems. Off-farm, there is potential to intercept leached nitrate before it enters surface waters via riparian strips or trenches, or in-stream removal by aquatic plants. In nitrate sensitive areas, there is a need to use a whole catchment approach by examining all contributions to nitrate leaching and not simply targeting one agricultural practice such as dairy farming.

Dietary effects on gene expression of lipogenic enzymes in mammary gland of lactating mice - Singh K; Harley DG; Grigor MR; McFadden TB (Proceedings of the New Zealand Society of Animal Production, 2000)
The effects of a fat-free or clofibrate-supplemented diet on gene expression of several lipogenic enzymes was investigated in mammary gland and liver of lactating mice. In lactating mammary gland, stearoyl CoA desaturase (SCD) mRNA expression was increased 2.1-fold (P<0.05) by feeding the fat-free diet, whereas clofibrate had no influence compared to control diet. Fatty acid synthase (FAS), acetyl CoA carboxylase (ACC), thioesterase II and lipoprotein lipase (LPL) mRNA levels in lactating mammary gland were unchanged after feeding the fat-free or clofibrate diets compared to control. In livers from lactating mice, the fat-free diet increased expression of SCD 5-fold (P<0.05) and FAS 10-fold (P<0.001) compared to control. ACC expression was unchanged by either the fat-free or clofibrate diet compared to control diet. These data show that, in lactating mammary tissue, expression of key lipogenic enzymes may be manipulated by diet, thus offering a potential means to modify milkfat composition.

Differences in wool characteristics in lines of sheep with high or low levels of backfat thickness - Merrick NC; Baird DB; McEwan JC; Purchas RW (Proceedings of the New Zealand Society of Animal Production, 2000)
Relationships between backfat thickness and wool characteristics for lines of Coopworth and Southdown sheep, selected for or against backfat thickness, were studied between years and between different age classes. On average, the lean Coopworth line grew 230 g more greasy wool (P < 0.001), which was 1.7 µm finer (P < 0.001) and less variable in diameter (P < 0.05) than the fat line. Other measured wool characteristics were not affected. The Southdown lines did not differ in fibre diameter, variability of diameter or curvature, within age groups. Southdown lambswool was finer (P< 0.001) than hogget or ewe wool (23.6 ± 4.9, 27.0 ± 5.6 and 26.7 ± 5.4). Fibre diameter differences observed in the Coopworth lines may have been a founder effect, as subsequent selection had little impact on it. Selection for leanness increased greasy fleece weight without affecting fibre diameter or staple length.

Economic benefit of using a major gene in a nucleus selection programme with limits on inbreeding - Amer PR; Villanueva B (Proceedings of the New Zealand Society of Animal Production, 2000)
This study investigates the commercial benefit of including information on an identified major gene in the estimation of breeding values for a breeding nucleus. Two types of selection (dynamic selection to maximise response with controlled inbreeding versus standard truncation selection) and two types of breeding value estimation (using versus ignoring information on a major gene) were compared over 15 generations. Selection strategies based on dynamic rules were commercially superior to strategies using truncation selection under comparable circumstances. Correction of the breeding values of selection candidates for the major gene resulted in extra genotype testing but was commercially superior to ignoring the major gene unless only small numbers of commercial males were sold. Small commercial breeding schemes adopting major gene selection will benefit from the application of selection algorithms that control inbreeding.

The effect of pasture silage quality on milk production and liveweight gain of dairy cattle - MacDonald KA; Nicholas PK; Kidd JM; Penno JW; Napper AR (Proceedings of the New Zealand Society of Animal Production, 2000)
Farmers in NZ have recently been encouraged to increase the quality of pasture silage they harvest. However, there was no New Zealand information available to ascertain the benefits of improved silage quality when it was offered as a supplement to grazing cows. Identical twin sets were divided into three groups in the winter, spring, summer and autumn during the 1998/99 season. Each group was offered a low pasture allowance and in addition, were offered 3 kg (winter) and 5 kg (spring, summer and autumn) DM/cow/day, of High, Medium and Low-quality pasture silage (nominally 10.4, 9.4 and 8.3 MJ ME/kg DM, respectively) as a supplement to pasture. In spring, summer and autumn offering a high quality silage increased milksolids yield from 1.57 to 1.78, 1.09 to 1.28 and 0.63 to 0.89 kg/cow/day, respectively (P<0.05) relative to cows offered Low-quality silage. There were no consistent live weight responses due to pasture silage quality. The spring, summer and autumn measured milksolids response can be calculated as having a net return (at $3.50/kg MS) of 6.7, 5.1 and 8.3 cents per MJME/kg DM increase.

Effect of sample preparation method on the validity of an early-life predictor of hogget wool bulk in genotypes used to develop GrowBulk sheep - Sumner RMW (Proceedings of the New Zealand Society of Animal Production, 2000)
Selection for wool bulk is normally undertaken in yearlings. In this study, a mixed-sex group of 170 GrowBulk sheep were wool sampled at 6 and 12 months of age. Measurements of fibre curvature and fibre diameter following degreasing a wool sample taken at 6 months of age with either water or solvent, explained 69% and 67% respectively of the variation in core bulk at 12 months of age. A combination of fibre curvature and fibre diameter measured following degreasing by either method was equally effective in predicting core bulk at 12 months of age. Precision of the predicted core bulk values was equivalent to direct core bulk measurement. Early-life prediction of core bulk from measurements of fibre curvature and fibre diameter taken close to the skin using consistent sample preparation methods, is a low-cost objective procedure to rank sheep for culling young sheep on wool bulk.

The effect of supplementation with 3-omega fatty acids on plasma metabolites and ovarian function of dairy cows - Meier S (Proceedings of the New Zealand Society of Animal Production, 2000)
Two- year- old Holstein Friesian dairy cows (n=20) were allocated to receive either a rumen- protected fish oil supplement (omega group, n=10), starting between 5-6 weeks post-partum, or pasture only (control group, n=10). .Serum metabolites, including cholesterol, urea, glucose and beta-hydroxybutyrate (BOH) were measured weekly from calving through to week 11-12 post-partum. Within 2 weeks of the commencement of treatment, serum cholesterol concentrations had increased significantly in the omega group vs the control group, and continued to increase through to weeks 11-12 post-partum. None of the other serum metabolites measured showed any differences with treatment. However, levels of serum urea, BOH and plasma glucose showed significant variations from week to week . The size of the dominant follicles and corpus luteum were measured, using transrectal ultrasonography, on days 8 to 16 of both oestrous cycles. The corpus luteum of the second cycle was significantly larger in the omega group. The second oestrous cycle was interrupted through an oxytocin challenge carried out to measure prostaglandin synthesis, on day 16 of the cycle. After the oxytocin challenge, the omega group exhibited a longer interval to the next observed oestrus. These results suggest that supplementing dairy cows with 3-omega fatty acids will result in changes at the site of the ovary and uterus.

Effect on milk characteristics to supplementing cows on a restricted pasture allowance with different amounts of either turnips or sorghum - Thomson NA; Clark DA; Waugh CD; van der Poel WC; MacGibbon AKH (Proceedings of the New Zealand Society of Animal Production, 2000)
The effect of supplementary feeding 0, 4 or 8 kg DM/cow/d of turnips or sorghum to cows offered a restricted pasture allowance (25 kg DM/cow/d) on milk characteristics (fat, protein and lactose, N fractions, serum proteins, fatty acids (FAP) and solid fat content (SFC)) was investigated. Thirty identical twinsets were used (10 cows/treatment) in a partial cross-over designed experiment comprising two, 10-day periods. Sorghum was higher in fibre (NDF, 65% v 23%), total lipid (3.5% v 1.5%) and similar for crude protein (9.6% v 12.0%) than turnips. Lipid composition differed between crops; turnips had more lauric (C12:0) and less linolenic (C18:3) fatty acids than sorghum. Differences in the chemical composition of the crop were reflected in different milk compositions. Milkfat content was lower for cows fed turnips than sorghum and the effect was greater (P<0.001) with increasing amount of turnips fed (5.5%, 5.1% and 5.0% for 0, 4, and 8 kg DM/cow/d respectively). Milkfat composition also differed for cows fed turnips compared to sorghum. With an increased amount of turnips fed, short, medium and long-chain fatty acids increased (P<0.001) and total unsaturated fatty acids decreased (P<0.001). As a consequence, SFC (an indication of milkfat hardness) also increased. Conjugated linoleic acid (cis-9- trans-11-C18:2) declined (P<0.001) as the level of supplementation with crop increased. The effect was greater (P<0.001) with turnips than sorghum. Compared with the fat components in milk the treatments had minimal effect on milk protein and nitrogen fractions. Feeding cows turnips compared to sorghum decreased (P<0.001) milk urea levels and increased (P<0.001) casein: whey protein ratio. This ratio declined (P<0.05) with increasing rates of supplementation with sorghum. These results show that different feed types can change milk components that influence the efficiency of milk processing, physical characteristics and nutritive value of the final dairy products.

Effects of an extract from sulla (Hedysarum coronarium) containing condensed tannins on the migration of three sheep gastrointestinal nematodes in vitro - Molan AL; Alexander R; Brookes IM; McNabb WC (Proceedings of the New Zealand Society of Animal Production, 2000)
The effect an extract of sulla (Hedysarum coronarium) containing condensed tannins (CT) had on the viability of the infective third-stage larvae (L3) of three gastrointestinal nematodes (Haemonchus contortus, Ostertagia circumcincta and Trichostrongylus colubriformis) was tested by the larval migration inhibition (LMI) assay in vitro. The LMI assay measures the ability of test material to immobilize larvae and prevent their migration through 20 mm nylon mesh sieves. The extract from sulla was added to rumen (RF) and abomasal fluid (AF), collected from sheep fed lucerne (Medicago sativa) chaff, to provide concentrations of CT similar to those observed in the rumen and abomasal digesta of sheep fed CT-containing forages (50-1000 mg/ml). Incubation of L3 larvae in rumen and abomasal fluid containing the sulla extract reduced the migration of larvae compared to those in control incubations (no extract added). This study showed that the larvae of T. colubriformis were more resistant (PO. circumcincta (RF 59%; AF 79%) and H. contortus (RF 72%; AF 81%) were significantly (PT. colubriformis (RF 37%; AF 26%). Addition of 2 mg polyethylene glycol (PEG)/mg CT to the incubations partially reduced the effects of the sulla extract on larval migration, particularly in the rumen fluid, suggesting that CT was responsible for most but not all of the inhibitory effect of this extract.

Effects of chromium picolinate on milk production and plasma insulin concentration in dairy cows - Peterson SW (Proceedings of the New Zealand Society of Animal Production, 2000)
Chromium picolinate (CrPic) is a biologically active molecule in which chromium is chelated to an isomer of niacin. It is claimed to reduce plasma cholesterol levels in humans, pigs and hens and to have beneficial effects on muscle and fat composition of humans, pigs and lambs. The metabolic responses recorded in lambs were similar to those observed in cows of high genetic merit for milk production, suggesting that CrPic may increase milk yields by altering aspects of glucose and insulin metabolism. The trial reported in this paper is work investigated the effect of supplementation with CrPic on milk yields and plasma insulin concentration in multiparous Friesian dairy cows grazing pasture. Preliminary measurements of milk yield and composition were made during a pre-treatment period of 1 week in 59 mixed-age dairy cows before separation into four treatment groups balanced for previous milksolids yield, live weight and condition. Beginning at peak lactation, groups received 0, 5, 20, or 100 mg CrPic/day administered once daily by oral drenching. Milk yields were measured and samples taken at weekly intervals for compositional analyses (fat, protein and lactose %). Blood samples were taken from the jugular at weekly intervals for insulin analysis. Chromium Picolinate had no effect on milk yield or composition. Plasma insulin concentrations did not differ between treatment groups.

Effects of condensed tannins and sesquiterpene lactones extracted from chicory on the viability of deer lungworm larvae - Molan AL; Duncan A; Barry TN; McNabb WC (Proceedings of the New Zealand Society of Animal Production, 2000)
The objective of this study was to determine the effects of condensed tannins (CT) and a crude extract containing sesquiterpene lactones (CSL) extracted from chicory (Cichorium intybus) on the viability of the first (L1) and third stage (L3) larvae of deer lungworm, Dictyocaulus viviparus in vitro using the larval migration inhibition (LMI) assay. The CT and CSL immobilised larvae and inhibited their migration through 25 mm nylon mesh sieves. Incubation of L1 larvae in rumen fluid (collected from deer fed pasture) containing 100, 400, and 1000 mg CT/ml, inhibited 12%, 28% and 41% of the larvae from passing through the sieves, respectively while the incubation of L3 larvae with rumen fluid containing the same concentrations inhibited 26%, 37% and 67% of L3 larvae from passing through the sieves, respectively. CT were more effective (P < 0.001) at reducing the viability of lungworm L1 and L3 larvae when added to the rumen fluid (pH 6.6) than when added to the abomasal fluid (pH 3.0). L3 larvae were more sensitive to the action of CT than L1 larvae. Addition of 2 mg polyethylene glycol/mg CT eliminated most of the inhibitory effect of CT against L1 and L3 larvae especially during incubation in rumen fluid. The CSL extract showed similar inhibitory activity in both fluids, indicating that this extract was not affected by the pH of the fluid, and they were more effective against L3 than L1 larvae.

Effects of diet on udder function and regression in Holstein-Friesian Cattle - Davis SR; Farr VC; Auldist MJ; Kolver ES (Proceedings of the New Zealand Society of Animal Production, 2000)
The rate of decline in milk yield after peak lactation is about 10% per month, for cows in New Zealand grazing pasture diets, and less than 4% per month in concentrate-fed animals in northern hemisphere environments. Much of the decline in milk yield after peak lactation is associated with a similar proportional loss of secretory cells from the udder and, once lost, these cells cannot be replaced until the dry period before the next lactation. Thus, we have found (unpublished data) that from peak lactation (October) to late-lactation in New Zealand, there was a loss of over 50% of mammary DNA. Such a loss was also reflected in changes in udder volume (Davis et al., 1985) and also in changes in milk storage capacity in the udder (Davis et al., 1987). Differences in lactational persistency between concentrate and pasture-fed animals suggest that nutrition exerts a long-term effect on milk production through maintenance of mammary secretory cell structures, as well as function. In the present experiment, our hypothesis was that cows fed concentrate diets would maintain milk production better than cows fed pasture over the summer months and that this would be reflected in the functional udder capacity (FUC). FUC is a measure of mammary cell numbers and is highly correlated with milk production (Davis et al., 1987). Further work attempted to correlate changes in FUC with concentrations of blood hormones sensitive to diet.

Effects of intensifying catchment land-use on the water quality of Lake Taupo - Vant B; Huser B (Proceedings of the New Zealand Society of Animal Production, 2000)
Levels of the nitrogen-dependent phytoplankton in Lake Taupo are currently very low, so the clarity of the lakewater is exceptionally good. This is because loads of nitrogen to the lake from the catchment are currently low (averaging 3–4 kg N/ha/yr). Changing to more intensive land-uses is likely to increase the nitrogen input. Converting 100–250 km2 of sheep/ beef pasture to intensive dairying yielding 30 kg N/ha/yr would increase the overall nitrogen load to the lake by 20–60%. This could cause phytoplankton levels to increase by a similar proportion, so that water clarity would fall by 20–40%.

The effects of shearing Finnish Landrace x Romney ewes in mid-pregnancy on lamb survival, birth and other weights - Smeaton DC; Webby RW; Tarbotton IS; Clayton JB (Proceedings of the New Zealand Society of Animal Production, 2000)
In each of 2 years, 600 Finnish Landrace x Romney ewes were subjected to a range of nutrition levels in early to mid pregnancy. Half the ewes were then shorn at day 70 of pregnancy with a standard comb. In the first year (1997), shearing treatment had no impact on single lamb birth and weaning weights, which were 5 and 29 kg respectively. Treatment improved twin lamb birth weights by 0.2 kg (P< 0.10), and weaning weight 1.4 kg (P<0.10). In the second year (1998), shearing treatment benefited single lamb birth weight (0.2kg; P< 0.10), and weaning weight (1kg; P<0.01) and improved twin lamb birth weight by 0.2 kg (P<0.01). In both years, lambing rate and survival were not affected. Ewe weaning weight, also in both years, was slightly higher in the ewes shorn at day 70 of pregnancy (P< 0.05).

Effects of yarding and transport on muscle glycogen concentration in beef cattle - Lambert MG; Knight TW; Cosgrove GP; Death AF; Anderson CB (Proceedings of the New Zealand Society of Animal Production, 2000)
Low ultimate-pH of beef is desirable because it enhances shelf life, colour and tenderness. Pre-slaughter stress is thought to deplete muscle glycogen and in extreme cases lead to higher ultimate pH of beef. Seventeen-month-old steers were allocated to three treatments (n=15): Control (C, grazing on pasture), Yarded (Y, held for 24 hours in cattle yards) and Yarded plus Transported (YT, as for Y but also trucked for 4 hours during the 24-hour yarding period). The Y and YT animals lost weight (average 25.5 kg) during time off pasture. Plasma glucose and lactate did not differ across treatments. Plasma cortisol and creatine kinase concentrations were increased by YT and plasma non-esterified fatty acids concentration by both Y and YT. Despite these indicators of occurrence of mild stress, especially in YT, muscle (longissimus dorsi) glycogen concentration was not influenced by treatments. Results suggest that increased emphasis on improved animal handling during yarding and trucking of cattle is unlikely to markedly lower the incidence of high-pH beef.

E-Genetics. The role of the internet in genetic improvement - Lindsay P (Proceedings of the New Zealand Society of Animal Production, 2000)
This paper reviews trends in the use of the Internet and e-commerce and outlines how this important new technology when coupled with modern Internet accesible databases will provide powerful new decision making tools to breeders andcommercial farmers.

Endocrine control of milk protein production in well-fed dairy cows - Mackle TR; Dwyer DA; Bauman DE (Proceedings of the New Zealand Society of Animal Production, 2000)
A hyperinsulinemic-euglycemic clamp was used to investigate the effect of insulin on milk protein synthesis in wellfed Holstein cows (n=4) with or without additional amino acids. Cows were fed a dry total mixed ration diet formulated to exceed requirements for metabolizable energy and protein. During abomasal water infusion, the insulin clamp increased milk protein yields by 15% (+128 g/d; P<0.01); when combined with abomasal infusion of casein plus branched-chain amino acids, milk protein yield was increased by 25% (+213 g/d; P<0.01). Concentrations of casein and whey proteins in milk were increased by insulin clamp treatments, with little change in their relative proportions. Providing amino acids without the insulin clamp had no effect on any production variables. Results confirm the important regulatory role of the endocrine system in milk protein synthesis and demonstrate the potential to produce milk protein is not fully expressed.

Experimental design for detection of quantitative trait loci for Facial Eczema in dairy cattle - Spelman RJ; Sellars MD; Sanders K (Proceedings of the New Zealand Society of Animal Production, 2000)
Three hundred and fifty farmers involved in the Livestock Improvement Corporation Sire Proving scheme (SPS) were surveyed, in May 1999, on the incidence of Facial Eczema (FE) in their herds. The SPS farmers were asked to score their 2- and 3-year-old SPS daughters on a five point scale; 1=not affected, 2=slightly affected, 3=severely affected (still alive), 4=culled due to FE and 5=died due to FE, and to comment on any calves or yearlings that were in categories 3 to 5. In the herds with at least one case of FE (50% of respondees), 89% of the animals were not affected, 5% were slighty affected, 5% severely affected and 1% were either culled or died primarily from FE. Heritabilities of 3-17% verified that FE in this dataset was controlled in part genetically and with the DNA bank for all SPS daughters, enables a QTL study to be undertaken. The proposed experimental design is an association study with the pooling of DNA for the 516 daughters that were scored 3 or higher. The control for the experiment would be paternal half sibs for each of the ‘affected’ daughters from the same herd, if possible. To detect linkage disequilibrium (LD) a panel of some 1000 microsatellites would be genotyped.

Factors affecting the sex ratio of dairy cattle in New Zealand - Xu ZZ; Johnson DI; Burton LJ (Proceedings of the New Zealand Society of Animal Production, 2000)
The sexes of calves born in 1996 (n = 319,539) and 1997 (n = 408,381) to artificial insemination in selected herds were analysed to study the effects of region, dam breed, dam age, semen type, semen breed, semen age, and sires on the sex ratio of calves. There was a significant (P < 0.001) effect of semen type on sex ratio; frozen semen resulted in 1.66% and 1.24% more male calves than fresh semen, respectively, in the 1996 and 1997 seasons. There was also significant (P < 0.01) variation among sires in sex ratio, but the heritability estimate for sex ratio was low (h2 = 0.02). No other effects were significant. Industry-wide use of fresh semen will result in more heifer calves from which future replacements can be selected.

Food markets of the future - Christie R (Proceedings of the New Zealand Society of Animal Production, 2000)
Looking from New Zealand at the food markets of the future, presents our industries with something of a challenge. To those with an industry background, this may seem an overcautious view. We are not altogether inexperienced as a food exporter, and can date trading in food products to well before colonisation. Today, over half New Zealand’s total merchandise exports are food products, and we can count most countries of the world as our markets for food products of some sort or other. So why would meeting these future markets be so challenging? First, our experience as a food exporter has largely been with commodities; only recently has New Zealand started to significantly differentiate and transform its exports into more sophisticated products. Second, the wealthy consumer markets even of today, are hugely more complex than they used to be, and consumers’ purchasing decisions are subject to many new influences, some almost totally unrelated to food, as such. Third, the control our exporters have over their food markets value chains is weak, and while this does not preclude us from participating, our returns are often constrained to f.o.b. margins, which will provide little more than a modest return on the capital we have invested in production systems. Last, some significant barriers to trade remain, in our most important markets. Some would describe these as intractable; suffice to say, progress in dismantling them has been painfully slow. All is not lost however. We are increasingly aware of the demands of future markets and, putting to one side the required action from our trading partners, we know what we need to do to lift our performance. Whether we have the will to change some historical behaviour and adequately re-configure the value chain in New Zealand remains to be seen; however, some radical surgery will be necessary. Of the many factors influencing the future shape of our food markets, technology is surely the most significant. E-commerce, and the dis-intermediation of our value chains that it is causing, is one example. The advances in food technology, biotechnology, and the ways in which we manage production systems are others. We need to understand and harness all these technologies. Market-related factors include rapidly changing lifestyles, the growing strength of food safety and animal welfare interest groups, and the need to be market-ready with consumer friendly, fresh products, all year round. New Zealand will need to do most things differently, and more quickly, to service our future markets with confidence.

Formulating total mixed rations from forages - defining the digestion kinetics of contrasting species - Burke JL; Waghorn GC; Brookes IM; Attwood GT; Kolver ES (Proceedings of the New Zealand Society of Animal Production, 2000)
The work described here is the first step in formulating forage-based TMR rations for dairy cows, based on digestion kinetics derived from in vitro and in sacco incubations. Kinetic information has been obtained from 23 contrasting fresh and conserved forages species, including temperate and tropical grass species, legumes (including Lotus spp. containing condensed tannins), herbs, silages, lucerne hay and maize grain. All forages were minced to a particle size similar to chewed material. Estimates of DM solubility (% DM) and fractional dry matter degradation rates (h-1) determined by in sacco incubations include: white clover (39%, 0.195), perennial ryegrass (45%, 0.114), tall fescue (46.8%, 0.051), paspalum (27%, 0.068), sulla (51.4%, 0.121), chicory (41.8%, 0.260), pasture silage (41%, 0.083), maize silage (28%, 0.042). In vitro incubations resulted in five-fold differences between forages in net ammonia release, 2-3 fold differences in volatile fatty acid yield and a three-fold difference in acetate:propionate ratio. The data will be used in simulation models to identify optimal forage mixtures for meeting the nutritional needs of high-producing dairy cows.

The future for small dairy farms: Constraints, plans and priorities - Parker WJ; Rauniyar GP; Dooley AE (Proceedings of the New Zealand Society of Animal Production, 2000)
Small dairy farms (<60 ha and/or <180 cows) represent about one third of New Zealand’s dairy herds. Declining real returns for milksolids (MS) and inflation are continuing to squeeze their profitability to the extent that, without change, many are likely to exit the industry in the next decade. A mail survey of 1389 farmers was conducted to quantify their plans for the future, the constraints they faced in improving farm income and ways the dairy industry could assist them. A response rate of 41% was achieved. The majority of respondents were over 45 years (74.4%) with the average age being 51 years. Most (85%) were happy with their farm location, but 48% said they were dissatisfied with their farm size. However, few would sell to buy a bigger farm elsewhere (17.8%) or to invest in non-farming activities (24.1%) Only 24% expected their children to continue dairying on the home farm. Few believed their own ability, others’ opinions or suitable learning opportunities were limiting their ability to improve farm income. Most believed expenses could be reduced very little (mean = 3.6%). However, MS production could be increased compared to current levels to a greater extent (mean = 15.8%, range 0 to 248%). Factors restricting the improvement of farm income were: the economic and political environment (s=2) (s=median score, where 1=strongly agree and 5=strongly disagree), unfavourable actions of the dairy industry (2), lack of capital (3) and environmental limitations (3). Plans for 2009 included: retired from farming (s=3), (where 1=very unlikely and 5= very likely), on the same farm but no longer dairying (3), no or minor change (2) and have a bigger dairy farm (2). Farmers’ priorities for using a 10% higher cash surplus were: debt repayment (s=4; as for previous scale), farm development (4), off-farm investment (3) and improvements to the family home (3). While potential exists to increase production on dairy farms with small herds, the survey indicates a considerable reduction in the number of these will occur over the next decade.

Genetic improvement and importance to sheep and beef farming - Davidson RM (Proceedings of the New Zealand Society of Animal Production, 2000)
The agricultural sector has undergone a large change in 15 years from 1985 to 2000. Changes in livestock numbers signpost the changes in agriculture and land use. Over 15 years of restructuring nothing has replaced agriculture’s contribution to GDP. The agriculture sector change has led to a more efficient sector at all levels and of particular note is the significant increase in sheep productivity. Following from this the potential for further sheep genetic improvement is discussed using the Meat and Wool Economic Service’s All Classes Sheep and Beef Farm to show farm potential.

Genetic manipulation to modify wool properties - Bawden CS; Penno NM; McLaughlan CJ; Walker SK; Hynd PI; Rogers GE (Proceedings of the New Zealand Society of Animal Production, 2000)
Over many centuries, genetic selection of sheep for particular meat and wool traits has made steady progress andgiven producers the opportunity to choose from a broad spectrum of well defined breeds. Selection for specific features ofbody frame or fleece has resulted in the emergence of true “meat” breeds (e.g. Poll Dorset, Suffolk, Texel) and other breedshighly valued for their fleece characteristics (e.g. Merino, Romney). Whilst such selection tends toward the outer limits ofgenetic variation among sheep, the sheep genome itself and natural mutation rates provide an inbuilt restriction to geneticchange and the appearence of new phenotypic varieties. In comparison, the use of transgenesis to add specific functionalsheep or non-sheep genes to the sheep genome has the potential to greatly expand the phenotypic range possible amongsheep. For example, in a preliminary sheep transgenesis experiment using a cortical type II keratin intermediate filamenttransgene, we have shown it is possible to alter fibre structure and properties. The fact genes from any species may be usedin the transgenesis process provides many experimental options simply not possible using the sheep genome alone. Thispaper is a discussion of some of the recent attempts to modify the genotype / phenotype of wool producing breeds usingtransgenesis. In particular, results of the earliest programmes designed to modify wool fibre properties and fibre growth rates are reviewed.

Genetic parameters for improvement of dual-purpose flock productivity with constraints on mature ewe body weight - Clarke JN; Dobbie JL; Jones KR; Wrigglesworth AL; Hickey SM (Proceedings of the New Zealand Society of Animal Production, 2000)
SIL provides opportunity for inclusion of information on mature ewe body weight in animal evaluations. This paper reports estimates of the parameters needed for these evaluations. Traits analysed were: weaning weight (WWT) and hogget liveweight in May (ALW); hogget yearling liveweight (HLW) and greasy fleece weight (HFW); and pre-mating body weights (ELW), number of lambs born (NLB) and greasy fleece weights of ewes at 2 to 5 years of age. EFW and especially ELW, were highly repeatable (>0.9), the pattern of genetic correlations suggesting that breeding ewes had reached maturity in these traits by 40 months of age. Direct and maternal genetic effects on WWT showed similar heritabilities (0.14±0.02 & 0.18±0.02) and were positively correlated (0.20±0.08). Maternal influences on traits measured at old ages were much reduced, direct heritabilities being similar to published estimates. WWT showed a high direct genetic correlation with LW8 and HLW (0.82±0.02), but lower with ELW (0.70±0.06 for 3-year old ewes). LW8 and HLW showed even higher direct genetic correlations with ELW (of the order of 0.90±0.02). EFW was highly correlated genetically with HFW (0.80±0.03), HLW (0.25±0.04), ELW (0.23±0.05) and LW8 (0.21±0.04). Dual-purpose genetic response predictions were derived using SIL’s recently revised relative economic values for a dual-purpose index. Its correlation with aggregate breeding value was 0.67. It predicted positive selection responses (per generation and standard deviation of selection pressure) in all traits: LW8 (2.1 kg), EFW (0.14 kg), NLB (0.038 lambs/ewe) and ELW (2.4 kg or 87% of the predicted single trait response despite the negative economic weight for this trait). Restraining the response in ELW to zero required a ten-fold increase in the negative relative economic value for this trait, and reduced the correlation of the index with aggregate breeding merit to 58% of its previous value. Such restriction greatly increased the relative contribution of fleece weight to economic response, made little difference to the contribution of NLB (although the absolute rate of progress was nearly halved), and reduced the contribution of growth; maternal effects on weaning weight became relatively more important.

Genetics of milk characteristics in New Zealand dairy cattle - Johnson DL; Petch SF; Winkelman AM; Bryant M (Proceedings of the New Zealand Society of Animal Production, 2000)
Data collection was integrated with LIC’s herd testing service using a sample of 102 herds involved in LIC’s SireProving Scheme (SPS) in 1995. In addition to milk volumefrom herd testing, the concentrations of fat, crude protein(total nitrogen), casein, whey and lactose were determined.The data was collected from over 3,000 cows born in 1996and first calving in the 1998 spring season, these beingpredominantly the daughters of approximately 220 SPSbulls. The milk characteristics were measured at three herdtests on each cow, with each herd having a herd test in eachof the Sept/Oct, Nov/Dec and Jan/Feb periods. Hereafter,we refer to these three periods as stages of lactation.

Global opportunities in agricultural trade - Cribb JHJ (Proceedings of the New Zealand Society of Animal Production, 2000)
In the 21st century the central issue of global security and human destiny will be food, land and water. There is already evidence that most conflicts now arise as a result of shortages, misallocation or abuse of these vital keys to human survival and prosperity. Over the coming 50 years the world will add another New Zealand to its population every fortnight. Demand for knowledge about how to produce food and manage landscapes sustainably will be unmatched in human history. But two nations, Australia and New Zealand, are superbly placed to meet such a demand. Many of the answers the world is seeking already exist in our labs and on our farms. The challenge now is for us to build the world’s leading knowledge export industry that specialises in sustainable food, land and water.

Heat challenge of dairy cows in the Waikato: a comparison of spring and summer - Bluett SJ; Fisher AD; Waugh CD (Proceedings of the New Zealand Society of Animal Production, 2000)
This experiment was carried out at the Dairying Research Corporation, Hamilton, New Zealand, to evaluate the heat challenge imposed on dairy cows during spring and summer. The diurnal temperature profiles of 18 Friesian cows were recorded over five days in November and five days in January. Temperature-humidity index and black globe temperature were used to assess the potential of the environment to induce heat stress. Cows in January had higher maximum (39.5 versus 38.9 ± 0.09 °C), minimum (37.9 versus 37.6 ± 0.09 °C) and mean (38.6 versus 38.4 ± 0.05 °C) daily body temperatures than in November, corresponding with higher ambient temperatures and solar radiation in January. Temperature-humidity indices were highest in January between 09:30 h in the morning and 19:30 h at night and within the range reported to cause mild heat stress in dairy cows (72 to 78). Respiration rate (47 versus 37 ± 1.4 breaths/minute) and water intake (51 versus 18 ± 2.3 l/cow/day) were both higher in January than in November.

Herbage quality and growth rate of single and twin lambs at foot - Litherland AJ; Lambert MG (Proceedings of the New Zealand Society of Animal Production, 2000)
Single and twin lamb growth rates, herbage mass and quality were monitored 3-5 times from birth to weaning on 6 farms in the southern North Island. Lambs (n = 50-80/farm) were tagged and weighed at birth, and ewes (n = 20-50/farm) grazing with the monitored lambs were tagged and weighed from docking. The average live weight gain (LWG) from birth to weaning was 273 g/d (229-311) and 220 g/d (152-279) for single and twin lambs respectively (P<0.001) and remained relatively static over the lactation period. Mean herbage energy concentration averaged 10.5 MJME/kg DM during the first two months of lactation but had declined to 8.9 by weaning (P<0.001). In conclusion, twin lamb growth rates on hill country are considerably lower than those of single lambs.

The human factor: Influence on livestock performance and welfare - Hemsworth PH (Proceedings of the New Zealand Society of Animal Production, 2000)
Research in the livestock industries in which animals have frequent contact with humans has shown that human-animal interactions can limit the productivity and welfare of these farm animals. Many of these interactions are routinely and, at times, habitually used by stock-people. While these interactions may appear harmless to the animals, this research has shown that the frequent use of some of these routine behaviours by stock-people can result in farm animals becoming highly fearful of humans. It is these high fear levels, through stress, that appear to limit animal productivity and welfare. This research has also shown that one of the antecedents of stock-person behaviour is the attitude of the stock-person towards interacting with his or her farm animals. Intervention studies in the dairy and pig industries have shown the potential of cognitive-behavioural intervention techniques designed to specifically target those attitudes and behaviours of stock-people that affect animal fear and, in turn, animal productivity.

The impact of liveweight and liveweight change on wool staple tenacity in Romney hoggets - Smith MC; Bray AR; Baird DB (Proceedings of the New Zealand Society of Animal Production, 2000)
Three lines of Romney sheep were selectively bred over 10 years for high or low staple tenacity, or were bred at random. Each crop of ewe and ram hoggets was weighed at strategic intervals throughout the year and staple tenacity was measured on mid side wool harvested in spring. Relationships of staple tenacity with live weight and liveweight change were examined by single and multiple regression analysis of data from a total of 2696 hoggets. The biggest single influence on staple tenacity in the ram hoggets was selection line, which accounted for 23.3 % (P2, but only 50 % of those with gains less than 20 g/day achieved that milestone. For the ram hoggets, the corresponding values were 66 % and 38 %. These findings provide a basis for liveweight targets to achieve chosen levels of staple tenacity in Romney hoggets.

Incidence of bearings in ewes that had a bearing the preceding lambing - Litherland AJ; Lambert MG; Knight TW; Cook T; McDougal DB (Proceedings of the New Zealand Society of Animal Production, 2000)
In the summer of 1998/9, 220 mixed-age breeding ewes were obtained from eight North Island farms. Half of these ewes had had a bearing in 1998 (PB ewes) and the other half were flock mates that had not (NB ewes). Ewes were fed in excess of their requirements from eight weeks before lambing and ewe condition had increased by 0.4 CS units by lambing. At scanning 15% of PB ewes were dry compared to 10% of the NB ewes. Pregnant PB and NB ewes also had similar scanning percentages (151% vs 142% respectively). Twenty percent of PB ewes had a bearing in 1999 (17% in single and 29% in twin pregnant ewes) compared with 0% in NB ewes (P<0.001). Pre-lambing bearings occurred 18 ±2 days (2-33 days) before lambing. There was a 5% bearing incidence after lambing. Eleven percent of the ewes treated for bearings died before lambing and 78% of surviving treated ewes produced a live lamb. In conclusion, high feeding levels in late pregnancy do not necessarily cause bearings. Ewes with bearings should be clearly identified and culled as they are more likely to have bearings the following year.

Increased ovarian response following pre-synchrony of superovulated red deer (Cervus elaphus) hinds - Scott IC; Asher GW; O'Neill KT; Littlejohn RP (Proceedings of the New Zealand Society of Animal Production, 2000)
The effects of two modified superovulation protocols on ovarian response in red deer were compared to a standard protocol. Twenty mixed-age red deer hinds were allocated to one of three treatment groups during the breeding season: Group S (n=7) received our standard superovulation protocol of 12-days treatment with an intravaginal progesterone-releasing device (CIDR‘, InterAg, NZ), eight injections of 0.45 mg ovine FSH (Ovagen, Immuno-Chemical Products Ltd., NZ) 12 h apart, beginning 72 h before CIDR removal with 200 iu eCG (Folligon, Intervet, Australia) added with the last injection. Group M1 (n=7) hinds received the same CIDR and eCG treatment, but Ovagen was delivered as four daily injections of 0.9 mg Ovagen dissolved in 30% polyvinylpyrrolidone (PVP-40; Sigma Chemical Co, USA). Group M2 (n=6) hinds were pre-synchronised using a 12-day CIDR‘ treatment and then received seven daily injections of 0.9 mg Ovagen dissolved in 30% PVP beginning four days after CIDR removal. A prostaglandin analogue (2 ml Estrumate, Pitman-Moore NZ Ltd, NZ) was administered concurrent with the sixth Ovagen injection. Ovarian response was highest in M2 hinds. Mean ovulation rates (±S.E.M.) were 4.9 ± 0.83, 3.4 ± 0.70 and 8.7 ± 1.20 for S, M1 and M2 respectively (P>0.05). Two S and three M1 hinds were anovulatory following superovulation treatment, but all M2 hinds ovulated (P>0.05). Pre-synchrony of red deer hinds before daily injection of Ovagen is an effective superovulation protocol. However, further work is required to ascertain if viable embryos are produced following the extended period of FSH exposure.

Involvement of calpains in postmortem tenderisation: A review of recent research - Geesink GH; Ilian MA; Morton JD; Bickerstaffe R (Proceedings of the New Zealand Society of Animal Production, 2000)
Tenderness is an important determinant of meat quality. Inconsistency and variability in tenderness have been identified as major problems for the meat industry (Morgan et al., 1991). It is well documented that tenderness improves during postmortem storage of meat but the mechanisms involved remain controversial. The general consensus is that proteolysis of structural muscle proteins causes tenderisation but alternative theories suggest that changes in the actin-myosin interaction (Goll et al., 1997) or a non-enzymatic effect of calcium on muscle proteins (Takahasi, 1999) or a rise in ionic strength (Ouali, 1990) may be involved. However, discussion of these theories is not within the scope of this review. With regard to postmortem proteolysis, the calpain system is thought to play a major role. Calpains are calcium-activated proteases with an optimum activity at neutral pH. In skeletal muscle, the calpain system consists three proteases, m-calpain, m-calpain and skeletal muscle-specific calpain, p94, and an inhibitor of m- and m-calpain, calpastatin. The involvement of calpains in postmortem tenderisation has been the subject of several reviews (Goll et al., 1991; Koohmaraie, 1988, 1992a, 1994, 1996; Ouali, 1990). Since these reviews, new information has become available which has provided answers to some of the questions on the role of calpains in postmortem tenderisation. The purpose of this review is to discuss some of these issues in the context of recent results. For further information on postmortem proteolysis and meat tenderness, or characteristics of the calpain system, the reader is referred to a number of excellent reviews (Penny, 1980; Greaser, 1986; Croall and DeMartino, 1991; Ouali, 1992; Sorimachi et al., 1994; Ono et al., 1998).

Lamb and ewe performance of East Friesian x Coopworths relative to pure-bred Coopworths - Jopson NB; Dodds KG; Knowler KJ; Wheeler R; McEwan JC (Proceedings of the New Zealand Society of Animal Production, 2000)
Purebred East Friesians (EF) sires were used in both the 1996 and 1998 matings (n=2 and 4, respectively) to generate 62 and 66 progeny for the two years. These animals were compared with approximately 1000 COOP lambs in each year for growth, ultrasonic fat and muscle depths, wool, dagginess, host resistance to internal parasites, and reproductive performance. For the 1998 mating, one F1 sire and 24 F1 dams were mated to COOP ewes and rams respectively to produce approximately 73 paternal and 33 maternal backcross progeny. Twenty four EF cross ewes were mated in each of the 1998 and 1999 birth years, and reproductive performance recorded. On average, the EF cross progeny had a live weight advantage (P0.05) after adjustment for live weight, but EF cross progeny had significantly lower C and GR measurements. EF cross progeny had lower fleece weight at 12 months (-0.46kg; P<0.001) than COOP. Average dag score differed between sire breeds with EF cross having lower scores (0.4 verses 1.2) compared to COOP. Sire breed differences in resistance to parasites were not significant. Analysis of the limited EF backcross data indicated positive EF direct and maternal effects for weaning weight, negative EF direct effects for dag scores, and negative EF direct and maternal effects for fleece weight. EF cross ewes performed significantly better (P<0.001) in lambs born per ewe lambing than the purebred COOP for both 2-tooth (2.57 cf. 1.84) and mixed-age (2.76 cf. 1.98) classes. The high lambing percentage in EF cross ewes meant that more than 70% of mixed-age ewes had three or more lambs per lambing, which could result in management difficulties. There was significant overlap in the sire-breed ranges for all traits, meaning selection of sire was more important than breed selection.

Lamb survival traits in Coopworth sheep selected for high or low backfat depth - Jopson NB; Greer GJ; Bain WE; Findlay JA; McEwan JC (Proceedings of the New Zealand Society of Animal Production, 2000)
Consumer preferences for lean healthy meat have driven genetic selection for leanness in the terminal sire and dual purpose sheep industries over the last 20 years. The Invermay Coopworth lean and fat selection lines were established in 1980 to study the effects of selection for live weight adjusted leanness on carcass traits, and the correlated responses in other traits. This paper reports the findings of two year’s data on lamb survival and performance in the lean and fat selection lines. Records were collected from 817 lambs comprising 325, 337 and 155 from the fat, lean, and a random-bred control line, respectively. Neo-natal mortality was not significantly different between the three lines, with approximately 93% of lambs born surviving until tagging. Lamb survival from tagging until weaning differed significantly between the selection lines (P<0.05), with fat line animals having 10.9% better lamb survival than lean line animals (95.5 verses 84.6%), after adjusting for differences in year, birth weight, birth rank, skin thickness, wool length, age of dam, mothering ability and ewe udder volume. Fat line lambs were 0.9 ± 0.1kg (mean ± SEM) lighter than lean line animals, with control line animals intermediate. Udder volume (as measured by water displacement) did not differ between the three lines. Mothering ability (as measured by distance from ewe to the new born lamb during handling in the field) did not differ significantly between the lean and fat lines. Fat line lambs had thicker skins than lean line lambs at the same birth weight (P<0.01), but had no difference in wool length. The differences in lamb mortality between the lean and fat lines cannot be fully explained by differences in birth weight, indicating some physiological difference between the lines affecting survival.

Live animal contribution to beef tenderness - Daly CC (Proceedings of the New Zealand Society of Animal Production, 2000)
Defining a production and processing system for beef that ensures a consistent and high quality eating experience remains a major challenge to the industry. While significant progress has been made in developing effective processing specifications to enhance quality and consistency, the control and manipulation of animal variability is not as well understood. By avoiding detrimental processing and ensuring a normal ultimate pH (>5.6), an analysis of the M. longissimus dorsi from 265 cattle failed to identify any significant toughness (<10kgf shear force) when the meat is allowed to reach final tenderness during conditioning. However, both the initial (at rigor) shear forces and rates of tenderisation were highly variable, and toughness can be attributed to insufficient ageing. Low initial shear forces were only partially explained by the structural properties of the raw muscle, and probably need to be understood in terms of the textural changes that occur during heating.

Livestock Improvement Corporation Lecture: Sustaining fitness and welfare in the dairy cow - Webster AJF (Proceedings of the New Zealand Society of Animal Production, 2000)
The ‘Animal Welfare Problem’ is, in fact, two problems. One is the problem as perceived by the general (human) public. This tends to classify words like natural and grass as ‘good’; words like intensive and high output as ‘bad’. According to this simplistic world view, the New Zealand Dairy Industry ranks as good; an image which is your advertising industry reinforces by happy pictures of Jersey cows grazing peacefully, sometimes, quite shamelessly, with calves at foot! The other, quite distinct animal welfare problem is that perceived by the cows themselves, which cannot be reduced to pretty pictures. My address will consider only this latter problem; the impact of modern feeding, breeding and management practices on the welfare of the dairy cow herself. It is for you to decide how this information may be used for the good of the dairy cow and the good of the dairy industry.

Liveweight gain of young sheep grazing tall fescue or perennial ryegrass swards of different white clover content - Hyslop MG; Fraser TJ; Smith DR; Knight TL; Slay MWA; Moffat CA (Proceedings of the New Zealand Society of Animal Production, 2000)
It is not clear whether the inherent qualities of tall fescue or the legumes grown with it are responsible for the wide range of liveweight gains in young sheep grazing these swards. The objective of this experiment was to determine the value of the white clover content in tall fescue swards relative to perennial ryegrass/white clover swards in respect to live weight gain in young sheep. Nine trials (ranging from 41 to 190 days) were conducted at AgResearch Poukawa and AgResearch Lincoln from spring 1995 to autumn 1997 using 15 animals as replicates in 19 treatments. Overall, live weight gains ranged from –87 to 366 g/head/day. Even small increases in clover content had large positive effects on liveweight gain of young sheep grazing both perennial ryegrass and tall fescue. At the same pasture mass and composition, all spring grazing liveweight gains were significantly greater than those in autumn (P<0.001). Tall fescue swards appear to sometimes produce higher liveweight gains than perennial ryegrass-based swards, but this is by virtue of growing more white clover, particularly in spring.

Manipulating processing to generate meat quality attributes appropriate for diverse markets - Simmons NJ; Daly CC; Gilbert KV (Proceedings of the New Zealand Society of Animal Production, 2000)
The optimal processing conditions for different meat quality attributes can often be conflicting. For example, conditions that maximise the rate of tenderisation may be responsible for increased drip and cooking loss, a reduction in colour stability and changes in textural characteristics. The conditions for optimal processing can therefore be defined as those conditions that establish the best compromise between conflicting meat quality requirements for different end-uses or markets. Methods of defining processing specifications tailored to defined endpoints are considered, specifically through the control of the rate of rigor mortis onset using combinations of electrical inputs and chilling regime.

A multifaceted approach to providing consumers consistent meat tenderness - Smith TPL; Wheeler TL; Shackelford SD; Stone RT; Casas E; Bennett GL; Keele JW; Koohmaraie M (Proceedings of the New Zealand Society of Animal Production, 2000)
A comprehensive program of research on the physiological and genetic basis of variation in meat tenderness has beenundertaken. Key processes of tenderization have been identified; intervention and testing protocols have been devised andevaluated, including calcium chloride injection and in-line tenderness testing/classification. Genetic loci influencing meattenderness have been detected, and DNA markers developed to aid selection and eventual identification of the allelicvariation underlying these effects. This combined effort is leading to management and production approaches to providinga consistent, tender meat product.

Muscle glycogen and blood parameters in genetic strains of Angus cattle - Morris CA; Lambert MG; Knight TW; Fisher AD (Proceedings of the New Zealand Society of Animal Production, 2000)
Angus selection and control herds in two long-term breeding studies were compared for muscle glycogen and blood parameters pre-slaughter. Trial 1 involved 3 years of bulls (n=85) from a yearling-weight (W) selection herd and a control (C1) herd, differing by 19% in yearling weight. Trial 2 involved one year of steers (n=45) from an experiment to increase age at puberty (A+ herd) or to reduce age at puberty (A- herd), relative to a control (C2) herd, with age at puberty differing from the C2 mean by 11% (A+) and -10% (A-). In Trial 1, muscle biopsies were taken for glycogen assay (Years 1 and 2), and blood samples were taken (Years 1-3) for creatine kinase, cortisol, lactate, non-esterified fatty acids (NEFA) and glucose; animals in Trial 2 (Year 2 only) were sampled at the same time as Trial 1. Samples were taken at 17 months of age (Year 1), 10 and 19 months (Year 2), and 19 and 20 months (Year 3, with an extra blood trait added). Muscle glycogen concentration was 19% higher in the W than C1 herd (P<0.05), and it was significantly lower in the A+ herd than in the other two herds (P<0.001). Cortisol (P<0.05) and glucose concentrations (P<0.01) were lower in the W than the C1 herd; NEFA was higher in the C2 herd than in the A- or A+ herds (P<0.05). No other blood parameters differed between herds. Repeatabilities for the 5 main blood traits in Trial 1 ranged from 0.14 to 0.38, being highest for creatine kinase (if excluding outliers), but repeatabilities were all low in Trial 2 (highest value only 0.13). The main conclusions came from Trial 1, in which most data had been collected, namely that across-year differences were found for 3 traits between herds (muscle glycogen, cortisol and glucose).

Myostatin, a negative regulator of muscle growth, functions by inhibiting myoblast proliferation - Thomas M; Langly B; Berry C; Sharma M; Kirk S; Bass J; Kambadur R (Proceedings of the New Zealand Society of Animal Production, 2000)
Myostatin, a member of the transforming growth factor-b (TGF-b) superfamily has been shown to be a negative regulator of myogenesis. However, the molecular mechanism of myostatin function is, so far, not understood. Here we show that myostatin is synthesised and proteolytically processed in myoblasts and that myostatin functions by controlling the proliferation of muscle precursor cells. When actively growing C2C12 myoblasts were incubated with myostatin, the proliferation of myoblasts decreased with increasing levels of myostatin. Furthermore, we show that the myoblast inhibition by myostatin is reversible, such that, myoblasts retain the ability to proliferate after myostatin protein is removed. FACS analysis revealed that myostatin inhibited myoblast proliferation through preventing the progression of myoblasts from the G1 to S-phase of the cell cycle. Thus, we propose that the generalised muscular hyperplasia phenotype observed in animals that lack functional myostatin could be as a result of deregulated myoblast proliferation.

New Zealand's food exports in the 21st century: whither the green option? - Campbell H; Fitzgerald R (Proceedings of the New Zealand Society of Animal Production, 2000)
Over the last 8 years, several major horticultural industries have engaged in a process of ‘greening’ their food exports. This has been achieved through the fostering of organic and/or Integrated Pest Management (IPM) systems. Our analysis indicates that the most successful greening strategy has taken a two-tier approach – with a peak organic product, and a more mainstream product using IPM to create residue free fruit. The two-tier approach can be demonstrated to have advantages over an exclusive focus on either greening option. These industry developments have emerged partly in response to new niche markets for green and healthy foods. These markets are increasingly influenced by two emerging trends. First, is the emergence of ‘green protectionism’ as a political strategy in the EU and Japan. By switching from price support to environmental support payments, and raising barriers to food imports on the grounds of food safety and environmental concern, governments can achieve the politically advantageous outcome of serving the interests of both domestic rural producers seeking protection from cheap food imports, and urban middle class consumers concerned about food safety and the environment. The second emerging trend is the intensification of ‘food scares’ during the 1990s. Social scientific analysis would suggest that certain features of a food scare ‘lock in’ a scare for a prolonged period of time. Currently, scares involving BSE and GM foods are locked in and must be accounted for in strategy export decisions. Evidence from successful horticultural export strategies suggests that a wider range of food export industries should be contemplating a two-tier greening strategy to survive these emerging trends in the global market.

Patterns of luteinising hormone release and embryo recovery following superovulation of cycling and anoestrous lactating dairy cows and in non-lactating cows - Verkerk GA; Taufa VK; Hooper R (Proceedings of the New Zealand Society of Animal Production, 2000)
Lactating dairy cows, either during postpartum anoestrus (LA; n=10) or returned to oestrous cyclicity (LC; n=10), and cycling non-lactating dairy cows (DC; n=10) were superovulated with follicle-stimulating hormone during a progesterone supplementation treatment, inseminated and embryos recovered non-surgically 7 days later. Blood samples were obtained during the period of oestrus to determine plasma concentrations of luteinising hormone (LH). Number of corpora lutea varied (14.6±1.6, 8.1±1.5, and 8.7±1.9 for LC, LA and DC cows, respectively; P<0.02), but not the total number of all ova and embryos, or the total number of transferable embryos per cow. There were no significant differences between groups in either mean time from start of sampling to peak LH (37.0±3.9, 34.5±3.6 and 36.2±4.5 hours for LC, LA and DC cows, respectively) or mean LH peak (12.5±3.6, 16.6±3.3 and 13.4±4.2 ng/ml for LC, LA and DC cows, respectively).

Performance by dairy cows grazing two perennial ryegrass cultivars - Westwood CT; Norriss MG (Proceedings of the New Zealand Society of Animal Production, 2000)
The effects of two high-endophyte perennial ryegrass cultivars (‘Aries HD’ or ‘Yatsyn 1’) on the performance of lactating dairy cows were investigated during a two-year trial. Spring calved cows (Year 1, n = 359; Year 2, n = 570) were allocated to one of two herds. Herds grazed the cultivars as part of each grazing rotation from November to May for the 1997/98 and 1998/99 seasons. Milksolids production was higher (P<0.001) from the Aries HD herd compared with the Yatsyn 1 herd (228 vs. 202 kg MS/herd/day, Year 1; 340 vs. 294 kg MS/herd/day, Year 2, Aries HD and Yatsyn 1 herds, respectively) (P < 0.001). Milk fat % and protein % did not differ significantly (P>0.1) between herds. Significantly (P<0.001) more body condition (+0.8 of one body condition score) and more live weight (+17 kg) was gained by cows grazing Aries HD during Year 2. Interval from start of mating to predicted conception tended to be longer for cows grazing Yatsyn 1 (+ 6 days) during Year 1 (P = 0.06). Significantly different cow performance from ryegrass cultivars that produce similar yields of dry matter may be due partly to differences in forage quality and endophyte toxins. Aries HD tended to be more digestible than Yatsyn 1 and was associated with lower concentrations of ergovaline, an alkaloid produced by Neotyphodium endophytes that has been associated previously with reduced animal performance.

Perspectives and role of Animal Production/Science in the New Millennium - Elvidge DG (Proceedings of the New Zealand Society of Animal Production, 2000)
Last year, as my first function as president of NZSAP, I was privileged to attend the AAAP meeting held in conjunction with the 8th World Congress on Animal Production in Seoul Korea. The theme of this congress was “Sustainability of animal production in the 21st century and the quality of human life”. Information presented showed that the world population will increase to and plateau at 9.5-10 billion by the year 2050, an increase of 60-70% over the present population. I had known that the world population is experiencing a period of exponential growth but I had not fully comprehended the impact and immediacy of the problem. I, like so many others, have largely ignored such information as being too far away in both time and location to be of great concern. However, in 6 months time we enter the new millennium and 2050 does not now seem so far off. Whether we like it or not, we cannot remain blissfully ignorant of the world situation. Modern technologies ensure within hours we know about any major event that happens in any part of the world.

The pharmaceutical scientists' role in animal production: An historical and future look at the evolving area of controlled drug delivery in animal production - Rathbone MJ (Proceedings of the New Zealand Society of Animal Production, 2000)
In the field of controlled-release veterinary drug delivery, the utilization of new routes of administration or the development of new delivery systems are of considerable interest. Indeed, because of the large number of production animals and the problems associated with the administration of drugs to these animals, the potential for utilizing novel routes of administration or for developing controlled release products are enormous. However, such a potential will only be fully realized if safe, practical and effective delivery systems are rationally designed and tailored to the end users needs through collaborative efforts between animal, veterinary and pharmaceutical scientists. The intent of this presentation is to summarize the state of the art of controlled release systems in the veterinary field. It also intends to provide an overview of recent developments in this area and to look toward the future to examine the directions in which veterinary pharmaceutics is heading. Examples of currently available and future veterinary controlled release drug delivery systems will be given and explained throughout the presentation including ruminal boluses, intravaginal devices, externally applied drug delivery systems, injectable and implantable systems.

Pre- and post-rigor treatment of intermediate pH beef to reduce toughness - Thomson BC; Auld MM; Simmons NJ (Proceedings of the New Zealand Society of Animal Production, 2000)
As injections of acid and calcium chloride solution reduce toughness in beef of normal pH (5.4 - 5.7) beef, these solutions may also tenderise intermediate pH (5.7 - 6.2) beef. Portions of intermediate-pH striploins from four bulls were allocated to the following treatments :- control, lactic acid (0.55 M, 10 % w/w, injected within two hours of slaughter) or calcium chloride (0.3 M, 10 % w/w, injected 20 hours after slaughter). The samples were stored at 15°C for 24 hours, then at - 1°C for a further nine days. 24 hours after slaughter the shear force of the lactic-acid-treated samples was nonsignificantly less than the control (12.7 vs 15.4 kgF). Nine days after slaughter, the lactic acid and control samples remained unacceptably tough, while the calcium chloride samples (7.5 kgF) were acceptable. Therefore, it may be possible to use calcium chloride to reduce intermediate pH toughness.

Prediction of DEVCo cut weights from chilled ovine carcasses using single-frequency bioelectrical impedance measurements - Jelenak A; Marchello MJ; Clarke RD (Proceedings of the New Zealand Society of Animal Production, 2000)
Single-frequency bioelectrical impedance (resistance and reactance) was measured from one hundred and thirteen chilled lamb carcasses. The carcasses were later cut into the DEVCo cuts and every cut was weighed. These cuts were: Legs, Loin, Rack, Shoulders, Shanks, Flap, Breast and Neck. The bioelectrical impedance data, together with carcass weight and temperature, were used to predict the weights of each of the DEVCo cuts. The best prediction was for the DEVCo Legs cut (adjR2 = 0.945), and the worst prediction was for the DEVCo Neck cut (adjR2 = 0.369). The data analysis revealed carcass weight to be the single best predictor of DEVCo cut weights, and that adding the bioelectrical impedance data did not improve prediction significantly.

Prediction of post-partum anovulatory interval in dairy cows - Clark BA; Chagas LM; Gore PM; Dow B; Verkerk GA (Proceedings of the New Zealand Society of Animal Production, 2000)
Changes in a range of metabolites and body condition parameters in lactating cows were measured during early lactation to determine if any key indicators or combination of key indicators could be used as a predictor of length of post-partum anovulatory interval (PPAI). Fifty-three cows in a range of body condition scores were involved in the trial which ran from calving to 10 weeks post-calving. Plasma non-esterified fatty acids (NEFA) and serum cholesterol, glucose, betahyroxybutyrate (BOH) and urea content were measured in weekly samples. Live weight and body condition score (BCS) were measured weekly.Cows were categorised into four groups. Three groups were based on the post-partum anovulatory interval (PPAI). PPAI was defined as the interval between calving and the first evidence of oestrus behaviour. The fourth group contained all the two-year-old cows only. There was a calving interval of 31 days from the first to the last cow to calve. The nadir for live weight for all groups occurred one week after calving. Animals with a shorter PPAI had higher live weights on all occasions, with live weight at week 5 having the strongest association with length of PPAI (P<0.001). Mean BCS was higher for animals with a PPAI<60 days. Plasma urea concentrations were associated with PPAI at weeks 3 and 4 (P<0.01). NEFA and glucose were correlated with PPAI at weeks 3 and 4 only, respectively. There was no association between cholesterol or BOH with PPAI. These results demonstrate that the selected variables do not contribute greatly to prediction of PPAI. Those measures which give the closest association with PPAI are live weight, BCS and age.

Preliminary beef carcass composition data from breed-crosses in a genetic marker trial - Morris CA; Cullen NG; Bottema CDK; Crawford AM; Hyndman DL; Pitchford WS (Proceedings of the New Zealand Society of Animal Production, 2000)
A collaborative project has been established in AgResearch and at the University of Adelaide to identify genetic markersfor carcass composition and meat quality traits in beef cattle. Two extreme breeds were used, Jersey (J) and Limousin (L).First-cross Jersey x Limousin bulls (X) were mated to cows of both breeds to produce three-quarter Jersey (XJ) and threequarter Limousin (XL) animals. A total of 261 and 155 back-cross cattle of both sexes were slaughtered as 2-year-olds atRuakura in the springs of 1998 and 1999, respectively. A further 400 cattle of the same back-crosses are under evaluationin Australia. Relative to the mean off-pasture weight and hot carcass weight of the XJ cattle slaughtered at Ruakura in1998 (404 and 202 kg), the corresponding XL means were 472 and 262 kg respectively, 1.8 and 2.6 phenotypic standarddeviations (s.d.) heavier. A series of carcass composition traits was obtained from the weights of saleable meat, trimmedfat and bone from individual joints on the right side of each animal, after 24 h in the chiller. Over all joints, the weights ofmeat, fat and bone (as a % of their total) were 66.6, 9.6 and 23.8 for XJ and 71.7, 7.1 and 21.2 for XL, representingdifferences of 2.8, 1.4 and 2.2 s.d. units respectively. Weights of high value cuts (% of side weight) were 50.4 for XJ and52.7 for XL, a 2.3 s.d. difference. Ratios of meat to bone were 2.80 for XJ and 3.93 for XL, a 5.5 s.d. difference. Standarderrors of all the above differences in s.d. units were 0.16. The largest differences between the two breed crosses for theabove traits were 2.8 and 5.5 s.d, for meat percent in the side, and for meat to bone ratio, providing good opportunities forgenetic marker studies. In the AgResearch animals, consisting of progeny from three sire groups, markers from over halfof the genome have been analysed so far. A significant marker has been identified for meat percent in the side. The twoinformative sires had the same genotype for this marker, and the difference between sire-derived alleles in their effect onmeat percent averaged 0.99 s.d. (F statistic for each sire, 45.47 and 8.84).

Preparation of fresh forages for incubation and prediction of nutritive value - Barrell LG; Burke JL; Waghorn GC; Attwood GT; Brookes IM (Proceedings of the New Zealand Society of Animal Production, 2000)
In vitro and in sacco digestion offers a rapid and inexpensive method for evaluating nutritive value of ruminant feedstuffs. This study compared the conventional freeze dried and ground (FD) preparation with chopping to 6-mm lengths (C) and mincing (M) to represent chewed forage. In sacco and in vitro comparisons were made with perennial ryegrass (RG), white clover (WC) and Lotus corniculatus (LC). The mean proportions of large (>1.0mm) and soluble dry matter (DM) for the three forages were: M, 0.38 and 0.44; C, 0.76 and 0.21; FD, 0.35 and 0.34 respectively. Disappearance of DM and crude protein (CP) during the first 12 hours of rumen incubation was substantially lower for chopped forages. Minimal lag times before the onset of protein degradation were observed following mincing. Yields of ammonia from proteolysis in in vitro incubations were lowest for C and usually highest for M preparations. Preparation also affected yield but not proportions of VFA. These data show that ranking of forages for digestibility is affected by preparation and mincing appears to be a more suitable preparation for assays than chopping and freeze drying and grinding.

Prevalence and incidence of subclinical mastitis in dairy ewes and goats - McDougall S; Pankey JW; Delaney C; Barlow J; Murdough PA; Watts JL; Scruton D (Proceedings of the New Zealand Society of Animal Production, 2000)
The prevalence and incidence of bacterial mastitis have not been determined for small milking ruminants in Vermont, USA. Milk samples were collected for bacteriology from each gland of 110 goats (6 herds) and 153 sheep (3 herds) within 24 hours of parturition and approximately 40 days later. The prevalence, incidence rate of new infection and the spontaneous cure rate were determined. Goats had a significantly higher prevalence of infection than sheep (P<0.05). Prevalance at parturition and 40 days later was 27.3% and 25.5% and 15.0% and 9.1% for goats and sheep, respectively. Prevalence of mastitis increased with age in goats (P = 0.08) but not sheep and differed among herds (P<0.05). It is concluded that there is variation among species and herds in the prevalence and incidence of mastitis

Prevalence of bacterial infection and somatic cell count of early postpartum milking goats - Anniss F; McDougall S (Proceedings of the New Zealand Society of Animal Production, 2000)
This trial aimed to identify the bacterial pathogens associated with caprine mastitis and to determine the prevalence of infection in early lactation. Milk samples for bacteriology and somatic cell count (SCC) were collected from both glands of 400 goats in four herds. Bacteria were isolated from 28% (222/800) of the total glands sampled. Coagulase negative staphylococcus (12.9%), Corynebacterium spp. (11.5%) and Staphylococcus aureus (1.4%) were the most prevalent isolates. Infected glands had a significantly higher SCC than uninfected glands (473 x 103 (399 -563 x 103) vs. 123 x 103 (112 -136 x 103), geometric mean SCC and 95% confidence interval; P<0.05). Infection increased SCC and the degree of increase in SCC varied between pathogens

A program to assess the efficiencies of sheep-meat production systems: A teaching aid - Purchas RW (Proceedings of the New Zealand Society of Animal Production, 2000)
A computer program written in Visual Basic within a spreadsheet was developed to illustrate how the efficiency of a sheep-meat production system varies when changes are made in any or all of 32 variables. System performance is expressed in monetary terms as either the efficiency (E) in dollars returns per dollar cost (with a break-even value of 1) or as a profit. Costs and returns for ewes, rams and lambs are taken into account, and all are expressed on a per ewe per year basis. A single per kilogram price for mutton is used, but for lambs, the proportion falling into various classes at any carcass weight is calculated using a specified GR/carcass weight relationship in a separate simulation program. Relationships within the E-program are based on published data, such as those in lamb feed requirement tables. This program has proved useful as an aid to evaluating some repercussions of making various combinations of changes to sheep-meat production systems.

Reducing fat colour in beef by grazing steers on turnip bulbs - Knight TW; Death AF (Proceedings of the New Zealand Society of Animal Production, 2000)
Feeding steers for 10 weeks on the residual turnip bulbs left after grazing the green tops off with lambs plus low carotenoid supplements, reduced carotenoid concentrations in the carcass fat by 38-43% and fat colour by 14-31% compared with steers grazing pasture. The steers on the turnip bulbs were fed a daily supplement of 0.5 x 10-1 IU of vitamin A in pelleted barley grain plus pasture silage, hay, and malting corms. The turnip bulbs comprised approximately 42-47% of the diet. The growth rate of the steers on turnip bulbs was higher (P < 0.001) than for steers on pasture (0.71 kg head-1day-1 versus 0.45 kg head-1 day-1). There were no effects of grazing the steers on turnip bulbs on the other meat characteristics measured, including the odour and taste.

The regulation of glycogen level in the muscle of ruminants by nutrition - Pethick DW; Cummins L; Gardner GE; Jacobs RH; Knee BW; McDowell M; McIntyre BL; Tudor G; Walker PJ; Warner RD (Proceedings of the New Zealand Society of Animal Production, 2000)
This paper discusses recent work by the authors which has investigated the nutritional regulation of glycogenconcentration in skeletal muscle of sheep and cattle. Several experiments are summarised which show a clear relationshipbetween the level of glycogen in muscle and the intake of metabolisable energy. This translates into strong seasonal effectson the level of muscle glycogen in pasture fed cattle that correlate with live weight change. The clear message is thatanimals destined for slaughter should be on a high plane of nutrition as this will contribute to an increased level of muscleglycogen at slaughter and so help alleviate the problem of dark cutting meat. Acute regulation of glycogen is moreproblematical since the rate of glycogen repletion in skeletal muscle is relatively slow and the scope for rapid dietarychange in ruminants is constrained by the need to allow rumen adaptation to high starch/sugar diets. However the suddenintroduction of a high energy diet (based on cereal grain) in the presence of a ‘rumen modifier’ to reduce ruminal acidosiscan increase muscle glycogen concentration within 1 week of feeding. The ability to further modify glycogen level inskeletal muscle using carbohydrate and electrolyte products is discussed. In particular the possibility of using oral glycerol/propylene glycol as a means for increasing blood glucose and so glycogen synthesis is proposed. Experiments to examine the effectiveness of MgO as a means for reducing the stress response are also discussed.

Relationship between intermediate pH toughness in the striploin and other muscles of the beef carcass - Simmons NJ; Auld MM; Thomson B; Cairney JM; Daly CC (Proceedings of the New Zealand Society of Animal Production, 2000)
Striploin (m. longissimus dorsi et lumborum) with ultimate pH values of 5.8 - 6.2 can be tough, and this toughness may persist despite prolonged ageing (> 45 days) although little is known about the effect of intermediate pH on other muscles. The aim of this work was to examine the relationship of intermediate-pH toughness in the striploin with other muscles. The shear force values were measured in seven muscles, collected from 20 heifers and aged at -1°C for 2, 7, 14, 30 or 60 days. The shear force of intermediate pH striploins after 2 days correlated with all other muscles except the chuck tender (m. supraspinatus) (Pm. longissimus thoracis) correlated with the striploin (P0.001). These results suggest that all muscles apart from the striploins and cuberolls from intermediate pH carcasses will tenderise to acceptable levels after 14 days of chilled storage.

The relationship between wool follicle density and fibre diameter is curvilinear - Scobie DR; Young SR (Proceedings of the New Zealand Society of Animal Production, 2000)
Records for wool follicle density and wool fibre diameter were obtained from ewes (n = 787) of 13 breeds and lambs (n = 543) of eight breeds and four crossbred combinations. The data were gathered as part of nine separate experiments from seven years. Mean fibre diameter ranged between 14 and 58 µm, while follicle density covered the range 6.5 to 95 follicles/mm2. There was a significant curvilinear relationship (P < 0.001) between individual animal means for fibre diameter and follicle density. The relationship was significantly different between ewes and lambs (P< 0.001). Furthermore, the relationship between breed means for density and diameter were compared with equivalent data from literature sources. The relationship was effectively the same for all sources of data (P = 0.455). A restricted range of data could have led some literature sources to suggest a linear relationship!

Role of reproductive technologies in reducing the time lag associated with the commercial application of genetic discovery in the sheep industry - Smith JF; Vetharaniam I; McCall DG; Tervit HR (Proceedings of the New Zealand Society of Animal Production, 2000)
The recent and escalating emphasis on gene discovery has major implications for genetic improvement of the NZ sheep industry. However, the long lag phase in the dissemination of new genetic material through current breeding structures is a major impediment to rapid uptake of the improvements. Effective reproductive technologies are considered necessary for achieving the desired rates of dissemination but there is little evidence of their practical and economic values. To provide evidence, a series of modelling exercises were undertaken. This involved defining a particular commercial outcome (advancing the pattern of lamb kill in Otago/Southland by 1 month without changing lambing date), deciding on the relevant genetic trait to achieve this (terminal sires with a 20% increase in mature size), modelling the rate of genetic gain using a number of breeding scenarios that included artificial insemination (AI) and multiple ovulation and embryo transfer (MOET), to determine the time required for sufficient commercial rams to be available to achieve the outcome. Selected scenarios were then chosen for more detailed modelling to ascertain the economic implications to the farm (Otago/Southland lamb finishing farm) and to the industry of adopting the technology. The advancement of the kill pattern by one month was worth $12,714 on the commercial farm. Based on a two-tiered breeding system (stud and commercial) without any reproductive technology it takes 26 years to achieve the outcome (assuming that the animal with this genetic advantage had been identified at the start). The use of AI at the stud level reduced this time by 11 years. The additional use of MOET on stud ewes gave a further reduction in time of 7 years and the application of AI using stud rams at the commercial level an additional 2 years. These results confirm the importance of reproductive technologies in reducing the lag phase in gene dissemination and their value to the industry. There is a need to further refine the efficiency and efficacy of the chosen technologies.

Rumen foam stability in cattle selected for low or high bloat susceptibility - Hurd SA; Wheeler TT; Morris CA (Proceedings of the New Zealand Society of Animal Production, 2000)
A simplified method to measure foam volume (V infinity) and stability (1/k2) was used to investigate the influence of saliva on foam properties and its relationship to bloat susceptibility. Significant differences in V infinity and 1/k2 were observed between samples of rumen fluid (within-sample CVs were 9% and 18%, while between sample CVs were 57% and 70% for V infinity and 1/k2, respectively). Mixing bovine saliva with rumen fluid or diluted clover juice resulted in a large increase in V infinity and 1/k2 (4.6- and 7.8-fold, respectively). This effect was strongly synergistic as saliva alone produced essentially no foam. The assay was used to quantify the efficacy of a paraffin-based anti-bloat drench (V infinity and 1/k2 were decreased by up to 4-fold and 6-fold, respectively). Saliva from non-bloating cattle, four each from herds bred for low- or high-bloat susceptibility, was measured for the effect on the foam parameters of a rumen fluid sample. No significant differences due to herd-of-origin were observed.

Search for a locus near to myostatin that increases muscling in Texel sheep in New Zealand - Broad TE; Glass BC; Greer GJ; Robertson TM; Bain WE; Lord EA; McEwan JC (Proceedings of the New Zealand Society of Animal Production, 2000)
In close collaboration with three Texel breeders, we initially genotyped 36 rams with 5 DNA microsatellite markers that are known to map around the myostatin gene in sheep. Of these 36 rams, progeny of 12 polymorphic sires (4 from each flock) were selected for further analysis. This selection was made on the basis of each sire producing more than 40 offspring which were accompanied by parentage records, live weights at weaning and 8 months of age, and ultrasonic measurements of fat depth and rib-eye muscle dimensions. Final progeny numbers from the sires chosen ranged from 45 to 115 per sire. The data was analyzed by regressing the observed measurements on the probability of which paternal grandparental chromosome was inherited at the myostatin locus. The results suggest that the region of the sheep genome near the myostatin locus affects muscling (P<0.05) and fat depth (P<0.05) in the progeny of 4 of 12 sires tested.

Seasonal variation of the fatty acid composition of milkfat from Friesian cows grazing pasture - Thomson NA; van der Poel W (Proceedings of the New Zealand Society of Animal Production, 2000)
Information collected at the Dairying Research Corporation milk composition laboratories on the fatty acid composition of milkfat spanning 1994/95 to 1998/99 dairying seasons has been summarised. The data comprised 1350 determinations in 18 different experiments from 965 individual Friesian cows that calved in July/August and grazed solely on pasture. A seasonal effect on fatty acid composition was observed. In general, concentrations of fatty acid groups and individual fatty acids were similar in spring and autumn but differed in summer. The ratio of an estimate of preformed (total fatty acids >C 17:0 ) and an estimate of de novo- (total fatty acids <C 16:1 ) synthesised fatty acids altered during the season. In early lactation (August), the ratio of preformed:de novofatty acids (P:S) was 0.76 declining to 0.51 by December and increasing to 0.80 by late autumn. The concentration of total unsaturated fatty acids followed a similar trend: 30.4% in August, 24.5% in December and 32.8% in April. In early lactation, milkfat from primiparous compared with multiparous cows had higher oleic acid (C 18:1 ), total unsaturated fatty acids and P:S ratio, indicating greater mobilisation of body fat. Conjugated linoleic acid (CLA) varied from 1-1.4% through spring, declined to 1.0% in summer and increased to 1.6% by April. The seasonal changes in milkfat composition reflected the seasonal trends in the characteristics of milkfat for processing. For example the softness of milkfat as calculated from a relationship previously established between fatty acid composition and solid fat content at 10 0 C (SFC10), varied seasonally. Milkfat was softer in late spring (SFC 10 , 53%) becoming harder (SFC 10, 61-63%) during December to February and softer (SFC 10, 54%) in autumn. The healthiness of milkfat, as describedby the concentration of unsaturated fatty acids and CLA, varied throughout the season. The lowest concentrations were insummer or in mid-lactation and the highest in autumn or late lactation. The information will be useful to manufacturers ofdairy products to target specific milkfat products to particular times of the year.

Sensitivity of ultimate meat pH to initial metabolite concentration when glycogen is not limiting - Vetharaniam I; Daly CC (Proceedings of the New Zealand Society of Animal Production, 2000)
The causes of variations in the ultimate pH of meat under conditions in which glycogen is in excess are considered using a model of energy metabolism in the post-mortem period. A key component of the model attributes the inhibition and ultimate cessation of glycolysis to the accumulation of lactate (which inhibits the regeneration of NAD+ via the lactate dehydrogenase reaction) rather than acidosis. The initial concentrations (concentrations at slaughter) of creatine phosphate, ATP, lactate, and also the buffering capacity of the muscle tissue are shown to affect the ultimate pH. The ultimate pH was particularly sensitive to initial lactate concentration and muscle buffer concentration such that increases in either resulted in an increase in ultimate pH. Variations in the initial conditions of muscle metabolites are attributed primarily to preslaughter physical exertions, while variation in muscle buffer concentration may be genetically linked.

Sheep Improvement Limited - Introduction - Geenty KG (Proceedings of the New Zealand Society of Animal Production, 2000)
The aim of Sheep Improvement Limited (SIL) is to facilitate cost effective genetic improvement across the New Zealand sheep industry in cooperation with the previously existing sheep genetic improvement schemes including Studfax, Flocklinc and Animalplan. Development of the new combined scheme began in 1998 with the formation of SIL as a joint venture company between the New Zealand meat and wool boards. A project team drawn from the existing schemes and their parent organisations (AgResearch, Lincoln University and Massey University) set about construction of a new database structure and genetic engine …

The Sheep Improvement Limited (SIL) genetic engine - Newman SA; Dodds KG; Clarke JN; Garrick DJ; McEwan JC (Proceedings of the New Zealand Society of Animal Production, 2000)
The Sheep Improvement Limited (SIL) genetic engine (GE) interfaces with the SIL national database. It calculates breeding values from data provided by the database and reports these back to the database along with adjusted deviations and genetic trends graphs. The SIL system is a distributed and modular design, with the database and the GE located on separate computers connected via the Internet. The individual GE components are also modular and version 2 consists of 6 separate goal trait modules: growth, meat, wool, reproduction, survival and host resistance to internal parasites. This modular design allows each goal trait module to be easily upgraded and additional modules can be added as required. The GE uses across flock and year multivariate animal model BLUP. Evaluations can be requested as required by the user via Internet access to the database. The size of the job submitted scales transparently up to requests involving more than 200,000 animals, sufficient for the largest across flock sire referencing schemes. The intention is that the system will be continuously extended and improved. Near term developments are likely to extend to across breed analyses, the inclusion of a facial eczema module, and improved diagnostics. In the longer term it is anticipated that information from genetic markers will be included.

Sheep industry structure and genetic improvement - Garrick DJ; Blair HT; Clarke JN (Proceedings of the New Zealand Society of Animal Production, 2000)
The sheep industry consists of a nucleus or ram-breeding sector that accounts for 1-2% breeding ewes and a commercial sector that relies on the ram-breeding sector for the supply of flock rams. The rate of genetic change in the whole industry is dictated by the rate of genetic gain in the nucleus sector. Increasing the size of the nucleus sector has little affect on genetic gain but increases the costs of genetic improvement. Industry structure is determined by the behaviour of breeders and farmers but there is often little individual incentive for these players to alter their practices despite overall benefit to the industry. The advent of performance recording, open-nucleus breeding schemes and the introduction of new sheep breeds have all resulted in modifications to the NZ breeding industry structure. The introduction of new biotechnology, notably DNA and cloning technologies could markedly alter future industry structure.

Sheep industry vision and SIL - Geenty KG (Proceedings of the New Zealand Society of Animal Production, 2000)
Declining global commodity price trends for meat and wool emphasize the need for greater genetic and production improvement across the sheep industry. In response to this, Sheep Improvement Limited (SIL), a joint-venture company between the Meat and Wool Boards, was set up to develop a national database and sheep genetic improvement system incorporating the three previously existing schemes, FlockLinc, Studfax and Animalplan. The SIL system began commercial operation late in 1999 and works on the basis of a wholesaler (SIL) - retailer (SIL bureaus) - customer (ram breeders and their clients) chain. Sheep production performance information flows into the database, is processed by a state-of-the-art genetic engine, and genetic improvement information goes back out to ram breeders and their clients, all via the internet. Studies have shown that some progressive breeders and breeder groups are already making up to two percent genetic improvement per year for lamb and wool traits. This adds up to a cumulative annual improvement in income in a 2,000 ewe commercial flock of about $2,450. Uptake of this rate of genetic improvement by 50% of commercial sheep farmers would result in around $20.8m greater national annual income from sheep.

Short-term physiological effects of refeeding 5 to 10-day-old calves after fasting and transport - Todd SE; Mellor DJ; Stafford KJ; Gregory NG; Bruce RA; Ward RN (Proceedings of the New Zealand Society of Animal Production, 2000)
The short-term physiological responses of 5 to 10-day-old calves to refeeding after 30 hours without food and up to 12 hours of transport were assessed by monitoring packed cell volume and plasma concentrations of total protein, glucose, triglycerides, urea and lactate. Samples were taken immediately before refeeding after three and 12 hours of transport and at the end of 30 hours without food, and in each case three hours later. Refeeding after fasting caused replenishment of plasma glucose concentrations to control levels and in some cases beyond. It was suggested that the overshoot in glucose concentrations, when it occurred, may have been caused by a temporary increase in insulin resistance as a result of metabolic adaptation to starvation. Refeeding after 12 hours transport also resulted in increased glucose concentrations. Thus, refeeding after transport and starvation was beneficial to the calves as it enabled rapid replenishment of depleted energy reserves.

Technology attributes for farm decisions - management of endoparasites - Tarbotton IS; Paine MS; Heath A (Proceedings of the New Zealand Society of Animal Production, 2000)
Nine regional focus group meetings were held with farmers to understand their views about endoparasite management. A software package (Decision Explorer) was used to enable participants to express their views on endoparasite management, collectively reason, debate and reach agreement on a diagrammatic model. This model summarised how participants viewed the cause and effect relationships for endoparasite management. The three areas explored in the group meetings were general management, regional differences and information gaps. Focus group findings were used to guide the development of a decision tool. An emphasis was placed on a planning approach following the farmer focus group meetings. This planning would benefit from professional service providers and parasitologists but development was guided by the farmer knowledge elicited through the workshops. Making the decision tool available in both hardcopy and electronic forms should enhance accessibility. The authors suggest there is a need to seriously consider the establishment of a National Advisory Committee for endoparasites. One possible framework for such a committee already exists in the Dairy Industry (the National Mastitis Advisory Committee). This committee would contain representatives from the appropriate disciplines and be responsible for leadership on endoparasite management.

Trait economic weights for genetic improvement with SIL - Amer PR (Proceedings of the New Zealand Society of Animal Production, 2000)
This paper outlines the construction of industry selection indexes for the SIL sheep genetic evaluation process. Traits of direct economic importance in New Zealand sheep production form goal trait groups with each goal trait assigned an economic weight for use in selection indexes. Goal trait group indexes are calculated as the sum of breeding values for each goal trait within the relevant group after multiplication by the relevant economic weight. Three overall indexes can also be calculated by combining goal trait group indexes. The three overall indexes include a Dual Purpose (DP) index, a Terminal Sire (TS) index and a Fine Wool (FW) index. Flexibility is offered to users through the ability to choose overall and goal trait group indexes presented in their results, and the ability to add new indexes to the system.

Urinary cortisol: An indicator of stress in dairy cattle - Morrow CJ; Kolver ES; Verkerk GA; Matthews LR (Proceedings of the New Zealand Society of Animal Production, 2000)
The measurement of immunoreactive urinary corticosteroids was validated as a method of monitoring adrenocortical activity in lactating dairy cows. The physiological relevance of the technique was validated by demonstrating that (i) injection of ACTH led to a significant increase in plasma and urinary corticosteroid concentrations, and (ii) the translocation of cows from pasture to a barn facility resulted in a 1.1- to 2.5-fold increase in urinary cortisol concentrations. Plasma cortisol concentrations exhibited a 15- to 33-fold increase above basal concentrations 30 mins after ACTH administration (2.98±0.35 vs 63.7±3.9 ng/ml plasma; mean±SEM; P<0.01). Monitoring urinary corticosteroid concentrations is a valid tool for studying and evaluating adrenal activity and acute stress in cattle.

The use of body measurements in cattle to predict future live weight - Webby RW; Boom CJ; Cameron CA (Proceedings of the New Zealand Society of Animal Production, 2000)
Farmers need to select cattle into final slaughter groups in advance. Traditionally combinations of live weight and eyeappraisal are used to make these selections. To improve this process, live weight, length from withers to top of tail, widthacross hook bones and depth from brisket level behind shoulder to top of withers were measured at 3-monthly intervals onAngus steers from 8 to 30 months of age. Of all the individual measurements, previous live weight predicted end weightbetter than any single body measurement. This was improved by including other body measurements selected using stepwiseregressions. Although no particular combination of measurements was best for all time periods the results showed thatlength, width and body depth added value to current live weight as selection criteria for drafting steers into final slaughtertime herds.

Variation of fibre and follicle characteristics related to wool bulk over the body of Perendale ewes: Implications for measurement of wool bulk - Sumner RMW; Craven AJ (Proceedings of the New Zealand Society of Animal Production, 2000)
Wool samples were collected prior to shearing in two consecutive years from 8 sites over the body of six adult Perendale ewes differing in wool bulk. A skin sample was collected from the same sites in the second year. Fibre curvature and fibre diameter explained between 67 and 94% the variation in core bulk at the different sites. No measured characteristics significantly reduced the unexplained variance across all sites. Intercepts for the relationship between fibre curvature and fibre diameter with core bulk at each site were significantly different but less than the confidence limits associated with core bulk measurement. There were no significant differences in the slopes of the same relationships across the eight sites. Use of a pooled relationship to predict bulk from fibre curvature and fibre diameter is a least-cost option to describe the bulk of a fleece.

Winter grazing management effects on beef finishing system performance - Boom CJ; Sheath GW (Proceedings of the New Zealand Society of Animal Production, 2000)
A beef farm systems experiment was conducted for 2 years in which winter grazing management of either a fast rotation (FR) of 45 days, or a slow rotation (SR) of 120 days was applied to eight small farms containing either rising-1yr, or rising-2yr Angus steers (15/farm). All farms were managed in a fast rotation (<35 days) during spring and summer.Average farm pasture covers at the end of winter were 563 (±80) and 347 (±53) kg DM/ha higher on the SR farms than the FR farms for the first and second years respectively. The FR steers at the end of winter were on average 26 (±4.0) and 22 (±4.2) kg heavier than the SR steers in the first and second years respectively. By late summer, the FR steers were 15 (±5.3) kg heavier and 2 (±5.6) kg lighter than the SR steers. There were no significant management interactions with age class. Live weight compensation of the SR steers was rapid during the first 6 weeks of spring. The results of this experiment show that winter grazing rotation length had little effect on the final live weight achieved by summer. However, between year differences showed that systems compensation during spring is dependent on pasture supply, pasture quality and stocking rate. With the ability of a whole-farm system to show compensation, a slow winter rotation is a low risk option if climatic uncertainty is an issue.

Amino acid supply to the small intestine of dairy cows fed pasture - Kolver ES; Carruthers VR; Neil PG; de Veth MJ; Jansen EBL; Phipps DE (Proceedings of the New Zealand Society of Animal Production, 1999)
Two experiments measured the quantity and quality of amino acids available for absorption by four dairy cows fed pasture. Experiment 1 compared a diet of ryegrass/white clover pasture offered ad libitum or at 75% of ad libitum intake during October. Experiment 2, conducted in December, compared an all-ryegrass diet with a diet comprising 100% ryegrass, or 50% ryegrass and 50% white clover. Treatments were assigned according to a 2x2 crossover design. Restricted feeding (Experiment 1) significantly reduced the total supply of amino acids to the small intestine by 23% (246 vs. 190g amino acid nitrogen/d). Compared to an all-ryegrass diet, a ryegrass diet which contained 50% white clover (Experiment 2) significantly increased the total supply of amino acids by 10% (284 vs. 259g amino acid nitrogen/d). For all four pasture diets, arginine, methionine, and histidine were identified, in that order, as being most limiting, supplying 67, 71, and 77%, respectively, of the absorbable amino acid requirement. The supply of absorbable lysine from all four pasture diets was found to meet requirements of dairy cows in early to mid lactation.

Amino acid utilisation by the mammary gland: Whole blood versus plasma free amino acid pools - Pacheco-Rios D; McNabb WC; Treloar BP; Barry TN; Lee J (Proceedings of the New Zealand Society of Animal Production, 1999)
Utilisation of amino acids (AA) by the mammary gland of dairy cows has been studied in order to understand the responses in milk protein production to alterations in nutrient supply. One approach has been the use of balance studies, in which the amount of AA taken up from the blood by the mammary gland is compared with their respective output in milk protein(s). Although it is generally accepted that the free AA pool in blood is the major precursor for milk protein synthesis, there are differences when plasma or whole blood arterio-venous differences (A-V) are used to measure the uptake of AA by the mammary gland. Arterial and venous blood samples were obtained at 2 h intervals from cows fed fresh pasture over two 12-h sampling periods. The samples were subdivided into whole blood (WB) and plasma (P) and analysed for free AA concentrations, which were used to estimate amino acid concentrations in the erythrocyte. There were no significant differences in the A-V calculated from WB or P for the majority of AA. Plasma A-V was significantly higher than WB for threonine (13.9 vs 8.9 nmol/g blood) whilst WB A-V was higher than P for isoleucine (26.9 vs 23.3 nmol/g blood) and tyrosine (11.8 vs 10.3 nmol/g blood). Assuming the differences in A-V between WB and P can be attributed to AA exchange with the red blood cell (RBC), significant (t<0.01) exchange from RBC to the mammary gland occurred for only isoleucine (15% of WB A-V) and tyrosine (14% of WB A-V). These results indicate that plasma AA concentrations are valid measures of the immediate free amino acid pool available for uptake by the mammary gland.

Angus selection-herd reproductive data: A genetic model for dairy cattle? - Morris CA; Verkerk GA; Wilson JA (Proceedings of the New Zealand Society of Animal Production, 1999)
A selection experiment with Angus cattle, established in 1984/85, has achieved a difference in age at puberty in heifers of 70 + 6 days (17%) between an `Age Plus` (i.e. high age) selection line and an `Age Minus` line. Currently three heifer calf crops (born in 1993-95) are being retained until 5.5 years of age, so that pregnancy rates in 5 mating seasons (and calving data in 4 seasons) on unculled females can be recorded. Genetic correlations between pubertal traits (from either sex) and heifer or cow reproductive traits have been calculated. Similar estimates were also derived from a pilot beef-cattle trial in 1980-85 using paternal half-sib data (230 sire groups), but no selection. The objective of this paper is to evaluate the merits of selecting on pubertal traits to improve reproduction, and to assess the possibilities of this type of selection in dairy cows. Correlated responses in the `Age Minus` herd, relative to `Age Plus`, include earlier pubertal development in half-brothers (+1.6 cm (5.2%) in scrotal circumference (SC) at 8, 10 and 12 months of age, P<0.001), an earlier mean calving date in cows by 3 days following an unchanged start-of-mating date, a 3-day reduced postpartum anoestrous interval (PPAI, adjusted for the earlier calving date), and a higher mean pregnancy rate (+4.7%, based on 1083 matings) in cows 2 years of age or more (P<0.05). All the genetic correlations between age at puberty in heifers and cow reproductive traits in our two studies so far have favourable signs (e.g. negative between age at puberty and pregnancy rate, or positive between age at puberty and PPAI), so that selecting heifers for earlier pubertal age would be consistent with increasing cow reproduction. Because selecting heifers for puberty is not very practical, selecting bulls could be more realistic. All the genetic correlation estimates between SC and cow reproductive traits in our two studies so far also have favourable signs. Additionally, genetic correlations between SC in bulls and age at puberty in heifers are negative (-0.21 ± 0.09 and -0.19 ± 0.20, respectively in the two trials cited above), so that bull selection for higher SC would reduce age at puberty in heifers and improve cow reproduction. Thus direct selection for precocious puberty in our Angus herd (predominantly by bull selection) has led to more fertile beef cows. It is suggested that the genetic correlations observed could be an initial model for dairy cattle, showing how selection-index traits on dairy animals at puberty could be used to correct for the inferior reproductive genes of some dairy cows.

Application of dual-energy x-ray absortionmetry for ovine carcass evaluation - Clarke RD; Kirton AH; Bartle CM; Dobbie PM (Proceedings of the New Zealand Society of Animal Production, 1999)
Twenty-four frozen lamb sides were scanned in a medical dual-energy x-ray absorptiometry (DXA) scanner, producing measures of fat, lean and bone mineral content for each side. These sides were then partially dissected into muscle, fat and bone and the whole sides chemically analysed. DXA measurements correlated well with chemical analysis for % fat (r2 = 0.92, rsd = 1.2%) and fat mass (r2 = 0.97, rsd = 163 g), protein (r2 = 0.98, rsd = 232 g). DXA estimates of lean, fat and weight for the leg region of each side were correlated with dissected lean (r2 = 0.96, rsd = 115 g) and fat (r2 = 0.93, rsd = 66 g) and scale weight (r2 = 0.99, rsd = 92g). DXA estimates of side and leg mass mirrored scale measurement to within measurement accuracy (~ 100 g). These results indicate that DXA may be used as a reliable method for measuring carcass composition and distribution.