Effect of selecting Perendale hoggets for loose wool bulk on fleece characteristics and wool end-product performance - Sumner RMW; Maddever DC; Clarke JN (Proceedings of the New Zealand Society of Animal Production, 1991)
Hoggets from the Massey University fleeceweight-selected (FW) line were previously shown to have lower sulphur (S) concentrations in midside wool than control (C) hoggets at 14 months of age. This study involved two experiments. The first examined wool S concentrations at different body positions in 14-month hoggets and the second examined midside wool S concentration and blood parameters in young lambs. In Experiment 1, 16 FW hoggets and 16 C hoggets were wool sampled at 11 positions over the body. The wool S concentration of FW hoggets was found to be significantly (P<0.01) lower than that of C hoggets (2.77% vs 2.94%). Discriminant analysis was used to classify hoggets to their respective lines based on wool S measurements. The combination of sites which most correctly classified the hoggets was the midside plus base of the tail. In the Experiment 2, 40 FW and 40 C lambs were wool sampled on the midside at 28 day intervals from 21 November (1 week before weaning) to 13 February. FW lambs had significantly (P<0.05) lower midside wool S concentrations of urea, but not of creatinine, than C lambs. Results suggest that wool S concentration and plasma urea concentrations may be useful genetic markers for high fleece production but that the ability to discriminate between animals of high versus low genetic merit for fleece weight on the basis of wool S will depend on the sampling position and age of animals.

The effect of sodium bicarbonate on yield and composition of milk from grazing cows in early lactation - Carruthers VR; Bryant AM (Proceedings of the New Zealand Society of Animal Production, 1991)
No abstract supplied

The effect of three allowances of red clover on Red deer fawn growth and liveweight change in lactating hinds - Niezen JH; Barry TN; Hodgson J; Wilson PR; Holmes CW (Proceedings of the New Zealand Society of Animal Production, 1991)
The binding of monoclonal antibodies (MAbs) of predetermined specificity to growth hormone (GH) can result in significant enhancement of the biological activity of the hormone in vivo. The topographic region on GH associated with the enhancement phenomenon has been localised to two proximate sites on adjacent loop regions by extensive peptide synthesis (sequences: 35-53 and 134-154). The application of these observations of GH and (ii) increased production parameters following administration of particular antibodies. The latter aspect has now been demonstrated in a number of animal models by the passive vaccination of animals with purified anti-peptide antisera or monoclonal antibodies. Production parameters affected in such experiments include growth rate, fat metabolism, diabetogenic activity and lactation in ewes. At the present time, it has been shown that peptide sequence 134-154 will elicit up to 80% high titre, immuno- positive responders in sheep. Monitoring the growth rate and other production parameters of lambs vaccinated with sequence 134-154 indicates improved growth and total protein characteristics. These observations, in conjunction with the development of methodologies for effective autoimmunization of animals, may provide a basis for the design of peptide vaccines to improve animals, may provide a basis for the design of peptide vaccines to improve animal production.

The effect of varying leafy sward height and bulk density on the ingestive behaviour of young deer and sheep - Mitchell RJ; Hodgson J; Clark DA (Proceedings of the New Zealand Society of Animal Production, 1991)
In dairy animals, the development and secretory activity of each mammary gland in the udder is regulated independently by local mechanisms sensitive to the frequency and efficiency of milk removal. Acute regulation of milk secretion occurs through autocrine inhibition by a secreted milk constituent, which may act by modulating the sensitivity of the tissue to circulating hormones. Sustained changes in milking frequency or efficiency are associated with modulation of secretory cell differentiation and, ultimately, the number of secretory cells. Elucidation of these local intra-mammary mechanisms offers the prospect of controlling milk secretion in a novel and more specific manner than has hitherto been possible.

Effects of daily larval challenge on the performance of breeding ewes from late pregnancy to post weaning - Brief Communication - McAnulty RW; Familton AS; Sykes AR (Proceedings of the New Zealand Society of Animal Production, 1991)
A CIDR was inserted into 72 ewes which were either early in the cycle (E; days 1-3), at mid cycle (M; days 7-9) or late in the cycle (L; days 13-15). Half of the ewes received either 0 or 300 IU of pregnant mares' serum gonadotrophin (PMSF) at the start of superovulation treatment. M ewes had two thirds as many ovarian surface follicles >1.5 mm diameter compared to E and L ewes (8.8 vs 13.6 vs 13.0; P<0.001). M ewes had approximately two thirds as many ovulations present 8 days later compared to E and L ewes (5.1 vs 7.7 vs 7.7; P<0.05). For ewes receiving 300 IU of PMSG as well as FSH, there was a significant regression of follicle number on ovulation rate (b=0.73

Effects of fasting and an opioid antagonist on food intake in lambs infected with intestinal parasites - Dynes RA; Poppi DP; Barrell GK; Sykes AR (Proceedings of the New Zealand Society of Animal Production, 1991)
A divergent selection experiment with Romney sheep, using plasma concentration of IGF-1 measured 4 weeks after weaning as the selection criterion, was initiated in 1986. From 111 ram lambs born and reared as twins, 4 with the highest level of IGF-1, 4 with the lowest level and 4 selected at random were used to create three lines (high, low and control). Each ram was randomly mated with 25 ewes. Data from 1986 (number of lambs=111), and two F1 generations (1988, n=241 and 1989, n=151) are presented here. Analysis of variance showed that date of birth, age of dam, rearing rank, and sex significantly contributed to variation in plasma levels of IGF-1. Expression of variation in plasma IGF-1 between years appeared to be influenced by variation in pasture supply. Residual correlations between IGF-1 levels and production traits were positive but of variable magnitude (weaning weight, 0.14 to 0.43; post-weaning growth rate, -0.07 to 0.24; fleeceweight, 0.27). Based on the selection differential generated by initial screening of rams and the average divergency between the high and low lines, realised heritabilities of 0.22 and 0.27 were obtained for plasma IGF-1 concentration in 1988 and 1989, respectively.

Effects of immunisation against LHRH on body growth, scrotal circumference, and carcass composition in yearling Red deer stags - Freudenberger DO; Wilson PR; Purchas RW; Barry TN; Moss BA; Trigg TE (Proceedings of the New Zealand Society of Animal Production, 1991)
Mammary tissues from virgin, prepartum and lactating ewes were examined by in situ hybridisation with a 35S labelled cRNA probe derived from the bovine alpha-lactalbumin gene. Expression of alpha- lactalbumin was absent in the virgin udders. In the pregnant gland, alpha-lactabumin expression was found in some secretory alveoli but not in others, even though they appeared histologically similar, containing milk or colostrum and fat globules. Fully lactating ewes have several levels of alpha-lactalbumin expression. In secretory epithelium, it was high in collapsed thick walled lactating alveoli, slightly less in distended thin walled lactating alveoli with homogeneous contents and absent from alveoli containing an abundance of large fat globules. Beta-cytophasmic actin expression was the reverse of this. These observations are intriguing and suggest a number of hypotheses. Firstly; that alpha-lactalbumin gene expression is linked to the long term secretory activity of cells and drops off once cells are resting or regressing. Secondly; that alpha-lactalbumin gene expression is highest in those alveoli which are "filling up" and lowest in those which are full or have just been milked out. That is, there are cyclical variation in expression. And thirdly; that there is distinct compartmentalisation in the lactating gland, and synthesis of alpha- lactalbumin mRNA (and the protein?) occurs in cells which synthesise little fat.

The effects of once daily milking as a management practice in late lactation - Lynch GA; Hunt ME; MacKenzie DDS (Proceedings of the New Zealand Society of Animal Production, 1991)
Five goats were milked hourly for 43 h on two occasions, on one occasion receiving injections of growth hormone (GH; 15 mg S.C.) after 4 and 28 h of the milking period and on the other occasion were untreated. Blood samples were taken before each milking, the latter facilitated by intravenous injection of oxytocin (100 m i.u.). Milk yield began to rise 4-5 h after the injection of GH and continued to rise for a further 8-9 h until a level of production 18% above the pre-treatment yield was achieved. Following the second injection of GH the yield increment was reduced such that by the end of the experiment the yield increase was 24%. In one goat the milk yield response was not sustained and these data were excluded from the above calculations. Plasma insulin-like growth factor-I (IGF-I) and insulin concentrations increased in a similar time-course to the change in milk yield following GH treatment but were relatively constant in control experiments. IGF-I and insulin content of plasma was approximately doubled by GH treatment by the end of these experiments.

The effects of oxytocin and bovine somatotropin on production of cows milked once a day - Carruthers VR; Davis SR; Norton DH (Proceedings of the New Zealand Society of Animal Production, 1991)
Milk from normally lactating goats contains on average 11 ng/ml IGF-I and 106 ng/ml IGF-II, as determined by specific radioimmunoassay. The present study was an attempt to determine whether IGFs in milk could have originated from the blood. 125 I labelled IGF-I or IGF-II was infused directly into one gland via a pudic arterial catheter for 60 mins and their appearance in milk followed for 720 min. A total of 5.2% of [125 I]IGF-I infused and 10.0% of [125I]IGF-II was recovered from milk from both glands. Radioactivity consisted of TCA precipitable material, which eluted from Sephacryl S-200 as free and protein-bound IGF, and TCA soluble material which probably represents degraded products of the peptides. The amount and time course of secretion of TCA soluble radioactivity in milk from both glands was similar, indicating degradation of infused peptide at textra-mammary sites. Maximum specific activity in milk from the infused gland occurred at 80-120 min for IGF-I and 120 min for IGF-II and was 2.5 fold higher than milk from the non-infused gland. The lower milk/plasma ratio for immunoreactive IGF-I compared with 125I labelled IGF-I suggests all milk IGF-I might be derived from the circulation whereas similar calculations with IGF-II suggests only 78% of milk IGF-II could be accounted for by its transfer from blood.

The effects of season and herbage mass on the nutritive value of prairie grass cv. Grasslands Matua and perennial ryegrass - Rugambwa VK; Holmes CW; Chu ACP (Proceedings of the New Zealand Society of Animal Production, 1991)
The properties of the milk serum protein alpha-lactalbumin are reviewed with special emphasis being placed on its central role in determining the lactose and water content of milk. Much circumstantial evidence suggests that artificial depression of alpha-lactalbumin synthesis should decrease lactose synthesis and that this will, in turn, decrease the water content of milk. Experimental evidence indicates, however, that patterns of alpha-lactalbumin gene expression in lactating ovine and bovine mammary tissue are complex and we should be cautious in making such predictions. Studies with transgenic mice expressing either elevated or depressed levels of alpha-lactabumin will be required to settle this question. In the meantime, a promising line of research is the investigation of dairy cattle carrying variant alpha-lactabumin genes. It is possible that correlations will be found between some of these variants and both the water content and protein yield of milk. Conceivably, selective breeding of cattle carrying variant proteins may prove a more practical means of altering alpha-lactalbumin synthesis than current transgenic techniques.

Effects of the digestibility of hay on milk production by cows grazing on restricted pasture - Sangsritavong S; Holmes CW (Proceedings of the New Zealand Society of Animal Production, 1991)
Two groups of 12 cows were fed and managed identically throughout the whole lactation, except that one group was milked twice daily, whereas the other group was milked only once daily. The cows were aged 3 years and older, and included 6 pairs of identical twins. Yields of milk, fat and protein were: 4320 and 2810 kg milk ; 208 and 144 kg fat; 162 and 110 kg protein for the twice and once daily groups respectively and the differences were significant. However in three pairs of twin cows, once daily cows produced more than 90% of the yield produced by their twice daily twin mates. Lactose concentrations were significantly higher for the twice daily group, 5.05 and 4.82% lactose. Somatic cell counts were significantly lower for the twice daily group throughout lactation, even though there appeared to be no difference in the incidence of infection measured at the end of lactation. The twice daily group lost weight and body condition during lactation, even though they appeared to eat slightly more feed than the once daily group which gained weight and body condition. The twice daily group had lower plasma concentrations of glucose during early lactation than the once daily group, but there were no differences in concentrations of calcium, magnesium or Beta hydroxybutyrate between the groups. The results show that although once daily milking does cause significant decreases in yields of milk and its components, some cows were only slightly affected. Selection of tolerant cows, plus appropriate management such as longer lactations and high stocking rates, may offer a useful method of increasing labour productivity and reducing costs of production.

Effects of two methods of fibre removal on the cold resistance of cashmere goats - Muller S; Holmes CW; Litherland AJ (Proceedings of the New Zealand Society of Animal Production, 1991)
Two hundred and six mixed age Angora x Feral (G4) does with a mean fibre diameter of 20.4 microns were randomly mated to three bucks with mean fibre diameter of 18.8 microns (Group 1) and three bucks with mean fibre diameter of 22.2 microns (Group 2) in June 1987. The progeny were shorn at 10 months (August 1988), 16 months (March 1989) and 22 months (August 1989) of age. The fleeces were measured for fleece weight, mean fibre diameter, yield by weight of down, and colour. Down weight was then calculated. The fibre was visually classed according to Mohair-Cashmere Warehouse fibre lines and an economic value put on the fibre. Group 1 progeny were heavier and had finer fleeces and lower down weights than group 2 progeny at all three shearing date. Group fleeces were 0.6, 0.9 and 1.0 micron finer and 71, 86 and 109 grams lighter than Group 2 at the three shearing dates respectively. Fibre diameter increased during the experiment to a greater extent in Group 2 (3.8

The efficacy of used CIDR devices for synchronisation of oestrus and post-mating treatment - Smith JF; Konlechner JA; Parr J (Proceedings of the New Zealand Society of Animal Production, 1991)
An upper limit to the force animals exert to server a bite maybe important in maintaining grazing momentum. Structural strength of accessible pasture components would then determine bite dimensions and weight. Pure perennial ryegrass turfs (surface area 0.1m2 x 0.1m soil depth), were manipulated by clipping to produce 3 pasture heights (5, 10 and 15cm) x 3 sward structures (varying in leaf to pseudostem ratio and bulk density). Six sheep grazed 4 turfs fixed to a force plate of each height and bulk density. Mean peak bite force, bite weight, bite depth, bite area, bite volume and grazed stratum bulk density were calculated. Peak bite force increased with sward surface height but significantly so only between 10 and 15 cm. Sward structure had no effect except on the 5cm sward treatment with the highest grazed stratum bulk density. Bite depth and bite weight increased with pasture height and were not influenced by sward structure at a constant height. Bite area was similar at all sward heights, but decreased as grazed stratum bulk density increased. On short swards, proximity to the ground restricted bite depth and bite weight rather than peak bite force. Low bite weights per newton bite force may constrain bite depth and weight rather than absolute peak bite force.

Evaluation of the feasibility of a juvenile MOET scheme in sheep - Rangel-santos R; McDonald MF; Wickham GA (Proceedings of the New Zealand Society of Animal Production, 1991)
An experiment was conducted at Massey University to measure potential growth rates of fawns and weight changes of hinds during summer, a period when growth is usually limited by adequate feed supply and/or quality. Thirty two lactating mixed age hinds and their fawns (average age 32.9 days) were blocks on calving date and randomly assigned to one of 4 treatments on the Massey deer unit. The treatments consisted of low (LC), medium (MC), or high allowance (HC) of pure red clover (6, 12 or 18 kg DM/hd/day) or 12 kg DM/hd/day of ryegrass/white clover pasture (CON). The corresponding stocking rates were 17.5, 8.7, 5.8 or 7.1 hind/fawn pairs/ha on the LC, MC, HC and CON treatments respectively. Treatments lasted for 61 days from 29 Dec until weaning on 28 Feb. Hinds and fawns were weighed bi-weekly. Weaning weights of the fawns were 51.3, 49.5, 46.7 and 42.8 kg for the HC, MC, LC and CON treatments respectively. This corresponded to fawn average daily weight gain of 461, 433, 380 and 333 g/day respectively. Fawn growth rates and weaning weights were significantly greater on all clover allowances than on the control (p<0.05). HC and MC treatments did not differ but were greater than LC (p<0.05). Hind weight changes followed a similar pattern. Liveweight gains for the hinds was 53, 58, 5 and -52 g/day for the HC, MC, LC and CON treatments respectively. All three allowances of red clover increased weight gain more than CON (p<0.09). HC and MC treatments did not differ but both were greater than LC (p<0.05).

An evaluation of the New Zealand Wiltshire sheep as a model for studies on the physiology of fibre growth - Parry AL; Pearson AJ; Morris R; Still L-A (Proceedings of the New Zealand Society of Animal Production, 1991)
In New Zealand, breeding values have been predicted using the method of selection index (Sheeplan, Beefplan, Animalplan) or variants such as a modified contemporary comparison (Dairy Cattle). Over the last decade, research systems for evaluating beef cattle, dairy cattle, sheep and pigs in New Zealand have increasingly made use of Henderson's mixed model equations. In appropriate circumstances, these equations give rise to evaluations which are best, linear and unbiased predictions (BLUP). This review compares and contrasts theoretical and applied aspects of evaluation using selection index and BLUP. An example is used to demonstrate the rationale of BLUP for evaluating animals with records in different contemporary groups such as across flocks or years.

Factors affecting beef finishing efficiency on pasture - McCall DG; Marshall PR (Proceedings of the New Zealand Society of Animal Production, 1991)
Nineteen cows, diagnosed 30 to 50 days after insemination as conceiving to a double ovulation and ranging in age from 2 to 8 years, were compared for possible signs of pregnancy toxaemia with a sample group of 18 single-ovulating single-pregnant controls, balanced for age. Blood samples were obtained on four occasions, between 2 and 10 weeks before the date when the first cow was due to calve. Blood samples were analysed for ferroxidase, albumin (A), globulin, total protein, the ratio of albumin to globulin, magnesium, beta-hydroxybutyrate (BOH), gamma-glutamyltransferase and serum or whole blood selenium (Se). There were significant differences between single-pregnant and twin-pregnant cows in the concentrations of A, BOH and whole blood Se. Least-squares means were as follows: A, 33.7 and 32.3 g/l; BOH, 0.46 and 1.62 mmol/l; and whole blood Se 887 and 737 nmol/l. The BOH data in particular were useful in identifying cows possible requiring extra veterinary supervision.

Factors influencing the time to onset of oestrus after synchronisation treatment in ewes - Smith JF; Konlechner JA; Parr J (Proceedings of the New Zealand Society of Animal Production, 1991)
The effect of varying the height and bulk density of the leafy zone of the sward on the ingestive behaviour of six 11 month old Red deer hinds and seven 14 month old Romney ewe hoggets was examined. Deer and sheep, confined to metabolism crates were randomly allocated 21 sward height x density combinations consisting of 7 heights (3-21 cm) x 3 bulk densities (0.19-0.75 mg DM/cm3). The Sorghum bicolor swards were grown in 42 x 30 cm trays and had a deep, stem free leafy zone. The required height of leaf was made accessible to animals by raising or lowering each sward relative to a horizontal grid of fine rods forming 3 cm x 3 cm squares below which animals could not graze. The two lower bulk densities were engineered by snipping out alternate rows, or rows and columns of plants. After grazing for at least 20 bites, bite depth, bite weight, grazed stratum bulk density, bite volume and bite area were calculated. The ingestive behaviour of deer and sheep was very similar in relation to height and bulk density. The positive effect of height on bite depth was on average 11 times as large as the negative effect of bulk density. Height had little or no effect upon bite area, while bulk density had a moderate, negative effect. On average a 100% increase in height or bulk density respectively resulted in a 64% vs only 21% increase in bite weight; reflecting the fact that bite volume increased in relation to H (39%) but decreased in relation to bulk density (18%). Thus height was the major determinant of bite volume and bite weight via its influence on bite depth.

Fertility of fallow deer (Dama dama) does following synchronisation of oestrus with CIDR devices or prostaglandin - Jabbour HN; Veldhuizen FA; Green G; Langridge M; Asher GW (Proceedings of the New Zealand Society of Animal Production, 1991)
244 cows managed as a single herd were divided into 4 balanced groups. Group A was milked once daily for the last 89 days of lactation, Group B 61 days and Group C 33 days. All cows including a control group milked twice daily, were dried off on the same date. After culling using commercial criteria the remaining 192 cows were milked twice daily in the subsequent lactation. Within one week of imposing once daily milking, daily yield of milk, fat and protein fell by 14.6-11.4%, 10.6-8.5% and 8.8-4.0% respectively when compared to twice daily milked cows. Once daily milking increased protein concentration and somatic cell counts. The relative falls in production observed seven days after the imposition of treatment remained until drying off with consequential reductions in total yield over the period of treatment. Once daily milking reduced the rate of liveweight loss in late lactation. Differences of up to 12.4kg liveweight remained between groups prior to calving in the subsequent lactation, but no differences could be detected after calving. Improve reproductive or productive performance was not observed in the subsequent lactation.

Fleece production responses to Merino fine wool index selection - Wuliji T; Dodds KG; Land JTJ (Proceedings of the New Zealand Society of Animal Production, 1991)
Two N.Z. sets of phenotypic and genetic parameters were used to compare expected genetic responses from index selection for an economic breeding objective favouring the lean and penalising the fat content of lamb carcasses. The effect of different economic values for lean relative to fat were examined over the range corresponding to the 'biological' objectives, weight-adjusted fat and lean growth rate. Particular attention was given to the magnitude and direction of responses in lean and fat. Increasing the economic emphasis on lean relative to fat progressively increased the lean response but was associated with an increasing fat response in an undesirable direction. Different measures of carcass fatness varied in their ability to discriminate among genes affecting fat and lean differentially when included in a selection index along with growth rate, and were superior to eye muscle depth. Good estimates of the relative economic values are required for derivation of optimum selection strategies, especially if indexes of low discriminating power are to be used for selection.

Four methods of harvesting cashmere from breeding does - Litherland AJ; Paterson DJ; Hamilton G; O'Neill K (Proceedings of the New Zealand Society of Animal Production, 1991)
No abstract supplied

Genetic parameters for New Zealand cashmere goats - Baker RL; Southey BR; Bigham ML; Newman S-AN (Proceedings of the New Zealand Society of Animal Production, 1991)
Lack of breeds suitable for commercial dairying is a constraint in Developing Countries (LDCs); however there is some progress. All Latin American Countries have nucleus herds of Holstein or Friesian, compared to 71% of Asian and 52% of African countries. The potential for more exports of animals to LDCs is high, but success will depend on support from exporters in their management. Holsteins born in LCDs will have a body weight at maturity about 125 kg (500-550 kg) lower than expected, lactation milk yield will be 30-50% lower, calving intervals 10-15% longer, age at first calving 25% later and duration of herd life .5 to 1.2 parturitions less. This breed needs feeding at least the equivalent of 2.2 multiples of maintenance in TDN. At this level milk yield will average near 6000 kg, calving interval 410-420 d, age at first calving 29-31 mo, fertility will be 1.8 services per conception and herd life 2.6-3.0 parturitions. This should still result in acceptable levels in both biological and economic efficiency. Imbalances in feeding, foot problems, seasonal breeding and milking sanitation appear among the most pressing problems.

Goat behaviour patterns in hill country - Greaves LA; Wedderburn ME; Pengelly WJ (Proceedings of the New Zealand Society of Animal Production, 1991)
No abstract supplied

Greenhouse gas production by ruminants in New Zealand: a serious problem, or just hot air? - Van Gardingen PR (Proceedings of the New Zealand Society of Animal Production, 1991)
This paper describes five genetic markers from the sheep genome. The polymorphic nature of these new markers, called microsatellites, is due to differences in the number of dinucleotide repeats at each locus. The advantages of these markers compared with other DNA markers are the speed and ease with which individuals can be analysed and the highly polymorphic nature of the loci. The five loci described in this paper had between 4 and 19 loci at each locus, with PIC values ranging from 0.41 to 0.90. It is likely that microsatellites will provide the next generation of parentage test for domestic animals as they are cheaper to perform and simpler to analyse than DNA fingerprints.

Growth, reproduction and fibre production of alpacas imported from Chile - Davis GH; Wuliji T; Moore GH; Bruce GD (Proceedings of the New Zealand Society of Animal Production, 1991)
No abstract supplied

Impact of potential change in climate and atmospheric concentration of carbon dioxide on pasture and animal production in New Zealand - Martin RJ; Korte CJ; McCall DG; Baird DB; Newton PCD; Barlow ND (Proceedings of the New Zealand Society of Animal Production, 1991)
Three groups of 10 ewes each were treated with Repromap sponges (MAP), Chronogest sponges (FGA) or Controlled Drug Release devices (CIDR) for 11 days. At withdrawal the delay time until oestrus, LH surge and ovulation was measured. There was no significant difference between the two sponge treatments in mean delay times although FGA treated ewes tended to be less variable in their activity. CIDR treated ewes commenced standing oestrus sooner than MAP and FGA treated ewes (30h vs 42h and 40h respectively P<0.001). Similarly the onset of the LH surge (31h vs 46h and 46h P<0.001) and ovulation (59h vs 69h and 71h P<0.001) occurred sooner in the CIDR ewes compared to MAP and FGA sponges.

The influence of sward structure on peak bite force and bite weight in sheep - Hughes TP; Sykes AR; Poppi DP; Hodgson J (Proceedings of the New Zealand Society of Animal Production, 1991)
The effects of oxytocin and bovine somatotropin (BST) on production of cows milked once a day (OAD) were assessed in late lactation. Seventy four cows were milked OAD for 28 days including 7 days adaptation, 14 days treatment, and 7 days post-treatment. Treatments were OAD controls, OAD plus 5 i.u. oxytocin injected intravenously each day or OAD plus 20 mg BST injected subcutaneously each day. An additional 20 cows were milked twice a day (TAD) throughout the trial. Production of OAD cows averaged 11% less than that of the TAD controls during the first week of OAD milking. Milk yield was significantly increased by 13% in BST treated cows but was not affected by oytocin. Cessation of both treatments resulted in a reduction in yield compared to the OAD and TAD control groups. The failure of oxytocin to increase yield was not in agreement with previous results, possibly due to a lower dose rate of oxytocin in the present trial. Increased yields in BST treated cows suggested that udder capacity was not constraining yield and that BST may override the inhibition of milk secretion which occurs with extended milking intervals.

Integrating pastoral venison and beef production - Cowie J (Proceedings of the New Zealand Society of Animal Production, 1991)
The wool described by the New Zealand Wool Board's auction data may be considered to be a vector space defined by axes which are the wool processing parameters. Analysis of this wool vector space gives indications of the relative economic values of the wool properties. Data from 1984 to 1990 has been analysed to give relative economic values and, although short term values vary considerably, there appear to be some longer term trends. Wool bulk as predicted from NZWB type shows a general increase in premium, and wool colour, described by objectively measured yellowness and brightness, has shown increased importance for determining wool price, with brightness taking over from yellowness as the more important of the two. The correlation between parameters in the range of wools offered at New Zealand auctions not only makes it difficult to determine the relative economic importance of the wool properties but limits the range of blend specifications a wool processor can work with. Hence although premiums are not always obvious, it is important to the processor that extremes of wool properties are available to allow the maximum flexibility when making up parcels of wool for processing.

Integrating sheep and goats - McCall L; Shaw D (Proceedings of the New Zealand Society of Animal Production, 1991)
There is a specialised market for lustrous wools. No objective measure of lustre is currently available. Elliott (1986) has suggested, on the basis of the correlation between loose wool bulk (LWB) and lustre (LS) in wools from a wide variety of sources, that measurement of (LWB) and average fibre diameter (AFD) might be a useful indirect selection criterion for lustre. The strength of the above relationships within flocks have, however, not been established. Mid-side samples were taken from complete flocks of ram hoggets (n=390). Clean scoured yield, average fibre diameter and loose wool bulk were determined on all samples. Each greasy sample was independently assessed for lustre on a 7 point scale by three experienced wool appraisers. Within flock correlations between LS and LWB ranged from 0.36 to 0.58 for the best assessor (mean 0.48), much lower than the values (>0.90) obtained in Elliott's study. Inclusion of fibre diameter failed to markedly improve the prediction of lustre score. The co- efficient of variation was lower for LWB (4.7%) and AFD (5.7%) than for LS (27.8%). The significance of these results for wool measurement and selection programmes will be discussed.

Karyotyping Booroola gene carriers - Lord EA; Hill DF (Proceedings of the New Zealand Society of Animal Production, 1991)
The success of a multiple-ovulation and embryo transfer programme involving five breeds of sheep (Danish and Finnish Texel, Oxford Down, Gotland Pelt, and the White Headed Marsh) was compared across two seasonal periods. Results for the incidence of oestrous, ovulation rate, embryo recovery rate, fertilisation rate, and for the survival rate of the embryos to scanning and lambing in recipient ewes, were compared. The ovulation rate (7.8

Lactation in transgenic mice expressing the ovine Beta-lactoglobulin gene - Wilde CJ; Clark AJ; Kerr M; Knight CH; McClenaghan M; Simons JP (Proceedings of the New Zealand Society of Animal Production, 1991)
The efficiency of winter feed use for weaner calf production was compared in a yearling heifer mating system compared to a 2 year old first mating system in traditional and dairy x beef cows. These computer modelling analyses illustrated, with yearling heifer mating compared to 2 year old first mating, that the total weight of calf weaned per unit of winter feed required is increased by only 2% (Angus dams) and 6% (Hereford x Friesian dams, HxF). With HxF dams compared to Angus dams, the total weight of calf weaned per unit of winter feed required was increased by 8% (2 year old first mating) and 13% (yearling heifer mating). Yearling heifer mating rather than 2 year old first mating within a traditional beef cow breed is questioned, when compared at the same winter feed requirement. The superiority of dairy x beef breeding cows on the basis of calf production from winter feed is confirmed by this analysis. Furthermore, this superiority is maximum when yearling heifer mating is also adopted.

Lactational Physiology Contract - Davis SR (Proceedings of the New Zealand Society of Animal Production, 1991)
Friesian cows (25 per group) were treated with excipient or recombinantly-derived bovine somatotropin (bST, 25 mg/day) by two- weekly injection of a controlled release formulation for 26 weeks commencing 7 to 11 weeks after calving. Responses in fat yield were significant during weeks 1 to 13 of treatment (spring/early summer) and weeks 21 to 25 (autumn) but not during the intervening dry summer period when pasture allowance was low. Ten randomly-selected cows per group were blood sampled (tail vein, 2 hours off pasture) in weeks 5, 9, 13, 17, 21 and 25 of treatment. Treatment of cows with bST significantly elevated plasma concentrations of immunoreactive bST (12.4 vs 18.5 ng/ml,Pooled se = 0.8 ng/ml, P<0.001) and insulin-like growth factor-1 (IGF-1) (178.5 vs 246.1 ng/ml, Pse = 7.5 ng/ml, P<0.001). Treatment x sampling date interactions were non-significant for plasma levels of both bST and IGF-1, reflecting parallel changes in the concentrations of these hormones across the treatment period. It is concluded that the inability of cows to respond to exogenous bST during periods of low pasture availability does not reflect a diminished IGF-1 response to bST at this time.

Lamb and hogget wool production from crosses of new and traditional sheep breeds - Newman S-AN; Paterson DJ (Proceedings of the New Zealand Society of Animal Production, 1991)
Seasonal wool growth and objective fleece characteristics were measured for a group of Texel, Oxford Down (Oxford) and Romney ewes at Hopuhopu Quarantine and Research Station and a group of Finnish Landrace (Finn) and Romney ewes at Flock House Quarantine and Research Station. The ewes were born in 1987 and aspects of wool production measured from November 1988 to August 1990. All breeds exhibited a seasonal pattern of wool growth with a late summer-early autumn maximum and late winter-early spring minimum. The seasonal amplitude of wool growth of the Oxford was less, the Texel similar and the Finn greater than the Romney. Average annual clean fleece weight of the Romney (100) was heavier than the Texel, Oxford and Finn (60, 59, 44 respectively). Oxford and Texel wool was shorter (69, 59 respectively), more bulky (157, 162 respectively) and of a similar mean fibre diameter and brightness compared with Romney wool (100). Finn wool was shorter (70), slightly more bulky (115), finer *(74) and similar brightness compared with Romney wool (100). Texel, Oxford and Finn wools all showed less yellow discolouration (92, 77, 70 respectively) than Romney wool (100). Calculated net wool returns for the Texel, Oxford and Finn ewes were approximately $7, $7 and $11 per ewe per year less than for the Romney.

Localisation of alpha-lactalbumnin gene expression in sheep mammary tissue - Molenaar AJ; Davis SR; Wilkins RJ (Proceedings of the New Zealand Society of Animal Production, 1991)
The feasibility of a juvenile MOET (multiple ovulation and embryo transfer) scheme in sheep was evaluated in three trials using 6-7 month-old animals. Ovulation rate was not affected by the dose (1.3 vs 1.1) or the time (1.5 vs 0.9) of PMSG administration, but it was higher in adults than lambs (2.0 vs 1.15, P<0.05) (Trial 1). Adults also showed a higher percentage of animals in heat (89 vs 60, P<0.05) and a higher percentage of eggs recovered (87 vs 56, P<0.05) or fertilised (82 vs 48, P<0.05). In Trial 2, a higher response was achieved with PMSG than FSH-P, Ovagen or PMSG + Ovagen (4.18 vs 1.78, 1.06 and 2.05, P<0.05). GnRH did not affect the ovarian response to gonadotrophins (2.29 vs 2.25, P<0.05). Embryo viability appeared higher in lambs treated with Ovagen alone. A combination of Ovagen + PMSG and with or without GnRH did not improve significantly (P<0.05) the response compared to the administration of PMSG plus GnRH (2.3, 2.8, 2.2 and 2.8 vs 1.7) (Trial 3). The superovulatory treatments involved failed to induce satisfactory ovulatory responses in these prepubertal sheep.

A modelling study of once-bred heifer beef production - Keeling PCB; Morris ST; Gray DI; Parker WJ (Proceedings of the New Zealand Society of Animal Production, 1991)
Sixteen cows were randomly allocated tot he two treatment groups; one was given high digestibility hay (57% DMD and the other low digestibility hay (52% DMD). Hay was available to appetite during the daytime, while the cows grazed on a common pasture allowance (12 kg DM per cow) at night. Cows offered high digestibility hay ate more hay (P<0.01) but less pasture (P<0.05) than those on the low digestibility hay. Pasture intake was reduced by 0.2kg DM for each increase of 1 kg DM eaten as high digestibility hay. Cows offered the high digestibility hay ate more hay (P<0.01) but less pasture (P<0.05) than those on the low digestibility hay. Pasture intake was reduced by 0.2 kg DM for each increase of 1 kg DM eaten as high digestibility hay. Cows offered the high digestibility hay produced slightly more milk than those on the low digestibility hay. This difference average 1.3 L per cow daily, but was significant only in week 1. The composition of milk did not differ between the two groups. The cows offered the high digestibility hay also gained significantly more liveweight. The data show that the quality of supplementary hay has an effect on milk production, but that the effect is smaller than might have been predicted because of the increased substitution of hay eaten instead of pasture by cows given the higher quality hay and because of increased liveweight gain by these cows. The probable economic value of high digestibility supplement is discussed briefly.

Non-milk constituents in replacers for calf rearing - Wilson GF; Brookes IM; Lynch GA; Billington AC (Proceedings of the New Zealand Society of Animal Production, 1991)
This study was carried out to investigate central nervous system pathways which may be involved in the depression of food intake exhibited by parasitised lambs. Ten lambs with intake depression (c.20%; p<0.05); as a result of chronic infection with 4000 T.colubriformis larvae/day together with 10 non-infected animals were used in a factorially designed experiment. The factors were a 24 h fast or no fasting followed by; saline solution (control), or 0.6 mg/kg brotizolam (blocks satiety signals at the ventromedial hypothalamus), or 0.125 mg/kg of naloxone (an opioid antagonist), all in a 2 ml volume given i.v. immediately prior to feeding. Trickle infection depressed mean daily intake by 20% (p<0.05), likewise short term intake was depressed by infection (p<0.05). Fasting stimulated both short term and daily intake by approximately 100% (p<0.001) and 12% (p<0.05) respectively. Naloxone depressed cumulative intake for up to 2 h (p<0.01 - p<0.001) while brotizolam stimulated intake at both 60 and 120 minutes (p<0.001). These results show that opioid signals stimulate food intake in lambs and that fasting will overcome the effects of parasitism on appetite in the short term. A lack of opioid signals may be a factor in parasite induced food intake depression.

Nutritional effects on fibre growth cycles and medullated fibre production in Angora goats - Nixon AJ; Saywell DP; Bown MD (Proceedings of the New Zealand Society of Animal Production, 1991)
Carcass composition data from 1430 carcasses were used to obtain prediction equations for lean weight and fat weight as a function of hot carcass weight (HCW) and GR measurements taken at slaughter. The equation to predict lean weight was: 0.316+(0.547 x HCW) - (0.070 x GR), R

Oestrous behaviour and luteal function in anoestrous red deer hinds treated with a GnRH analogue or oestradiol - Duckworth JA; Barrell GK (Proceedings of the New Zealand Society of Animal Production, 1991)
Five-year old Coopworth pregnant twin bearing ewes were allocated to four periods of treatment which commenced either -4, 0, 6 or 12 weeks from lambing periods 1 to 4, respectively. Within each period, pregnant ewes were further allocated to one of two groups (n+6) one receiving 4000 Ostertagia(Teladorsagia) circumcincta larvae per day for 30 days (MCI) or no infection (NIC). All ewes were housed indoors and offered a pelleted diet. Faecal egg counts, ewe liveweight, food intake, milk production and serum pepsinogen were determined weekly. Wool growth, fibre diameter and tensile strength were determined on wool grown within each experimental period. Abomasal damage, as judged by serum pepsinogen, occurred during all periods of infection. The magnitude of production losses varied with time of challenge. Parasitism reduced milk production by 10-59% (p<0.01) and wool staple strength by 29-44% (p<0.01) with greatest effects on wool staple strength being recorded during period 1. During lactation food intake (p<0.01) was reduced by 30% in period 1 by parasitic infection but little effect was seen prior to parturition. These data confirm that significant production losses do occur in breeding ewes. The effects on ewe production of any larval challenge will depend on the timing of the challenge will depend on the timing of the challenge and on the susceptibility of the ewe to infection at that time.

Optimization of 'herd-in-calf rate' with respect to the length of the postpartum anoestrous period in Angus cows suckling calves - Pleasants AB; Barton RA; Morris ST; Anderson WJ (Proceedings of the New Zealand Society of Animal Production, 1991)
A trial was undertaken to evaluate the effectiveness of the CIDR-B in buffalo. Twenty four, 20 month old buffalo heifers had CIDR's inserted (day 0) for 12 days. Each heifer was injected intramuscularly with 10 mg of oestradiol benzoate at CIDR insertion and 150 IU of PMSG at CIDR removal. Two buffalo bulls fitted with chin ball harnesses were introduced into each of 2 groups of 12 heifers. Continuous observations of mating activity commenced 24 hours after CIDR withdrawal. The heifers were bled for progesterone analysis on days -20, -9, 0, 2, 7, 12 and 26.9 CIDR's (38%) lost from the heifers were replaced immediately after the losses were noticed. The mean interval from CIDR removal to onset of mating activity was 50.3

Out-of-season embryo transfer in five breeds of imported sheep - Greaney KB; McDonald MF; Vivanco HW; Tervit HR (Proceedings of the New Zealand Society of Animal Production, 1991)
Three groups of 2th Romney wethers were given 0, 12g ZnO fortnight-1 and 12gZnO week-1 respectively for 18 months. Plasma trace element levels were monitored regularly over this period. At the end of the trial the animals were slaughtered and various organis, muscle, skin and wool were removed and analysed for a wide range of elements and for metallothionein. Zinc treatment resulted in significantly elevated Zn in plasma, red blood cells, liver, kidney, intestine and pancreas. Copper concentrations in liver (272

Oxygen consumption and the energy costs of Na+, K+ -transport in the rumen of Holstein-Friesian steers - Kelly JM; McBridge BW; Milligan LP; Waldo DR (Proceedings of the New Zealand Society of Animal Production, 1991)
The nutritive value of perennial ryegrass (RG), low mass Matua prairie grass (LM) and high mass Matua prairie grass (HM) swards were measured during early spring, late spring, summer and autumn of 1987/88 and 1988/89. Pre-grazing herbage masses were approximately 3000, 4000 and 5500 kgDM/ha for RG, LM and HM swards, respectively. Lactating cows on a common herbage allowance (50 kg DM/cow daily), grazed the ryegrass and Matua swards at mean intervals of 25 and 35 d, respectively. Values for the concentration of N (% OM) and DMD in whole plants, average across all seasons, were (%N) 2.6, 2.5 and 2,3, and (% DMD) 71.4, 71.1 and 69.4, respectively, for RG, LM and HM. The values for HM were significantly lower than those for the other two treatments. Values for the concentration of N and DMD in green grass leaf were (%N) 3.4, 3.5 and 3.5, and (% DMD) 72.4, 71.9 and 71.5, respectively, for RG, LM and HM. There were no significant differences in % N between the three treatments; the differences in % DMD between RG and HM was significant. During the autumn in both years, the LM treatment had a higher value for DMD % than the RG treatment (by 3 to 6% units). These results indicate that even at high pre-grazing herbage masses (4-5 tDM/ha) Matua prairie grass plants maintained relatively high nutritive values in green leaf and stem.

Plasma hormone concentrations in pasture-fed Friesian cows treated with recombinantly-derived bovine somatotropin (bST) - McCutcheon SN; Hoogendoorn CJ; Lynch GA; Wickham BW; Breier BH; Gluckman PD (Proceedings of the New Zealand Society of Animal Production, 1991)
Dairy farmers often debate the importance of liveweight of rising 2 year old heifers and the value of various heifer wintering systems on subsequent production. Lifetime performance of all dairy cows born on the Taranaki Agricultural Research Station have been recorded since 1978 on a computerised data base. This data base was utilised to determine the liveweight gain of heifers and cows over winter and the effects of this on production in the following season. Initial analysis of the data showed a significant (P<0.01) age effect on winter liveweight gain within a mixed age herd of cows. The average liveweight gain over eight years of the older cows (4 yr +) was 3 times that of the rising 2 year olds. Further analysis showed a significant (P<0.05) age effect on the relationship between liveweight at calving and production of milkfat in the following season. Higher liveweight at calving resulted in a greater increase in production for 2 year olds than for older cattle. The conclusion to be drawn from this is that wintering rising 2 yea old heifers separately from older cows to achieve higher liveweight may have beneficial effects on the following seasons production. A field trial in winter 1990 to test this assumption showed the winter liveweight gain of rising 2 year old heifers and mature cows, offered the same herbage allowance, was significantly (P<0.01) higher when wintered separately than wintered as a mixed age herd. Subsequent milk solids production from the two-wintering systems was the same despite different liveweight at calving. Aspects of herd behaviour were suggested as the cause of the nil response.

Relative economic values of wool processing parameters - Maddever DC; Carnaby GA; Ross DA (Proceedings of the New Zealand Society of Animal Production, 1991)
Seasonal wool growth pattern and fleece characteristics of Doreset x Romney ewes lambing in either autumn or spring and rearing 0, 1 or 2 lambs were measured over 2 years. The ewes were shorn twice- yearly in March and October. Season of lambing influenced the seasonal pattern of wool growth. Autumn lambing ewes did not show as marked a seasonal decline in wool growth during the winter. March shorn fleeces were coarser (2.5 um), stronger (20 N/ktex), and yellower (1.1 Y-Z units) than October shorn fleeces of October shorn spring lambing ewes. On the basis of price trends over the last 5 years, net wool returns from autumn lambing ewes would exceed those from spring lambing ewes by approximately 80c/ewe/year.

Responses to divergent selection for plasma insulin-like growth factor-1 (IGF-1) in sheep - Morel PCH; Blair HT; McCutcheon SN; Breier BH; Gluckman PD (Proceedings of the New Zealand Society of Animal Production, 1991)
No abstract supplied

Ribozyme mediated modification of alpha-lactalbumin gene expression - L'Huillier PJ; Bellamy AR; Davis SR (Proceedings of the New Zealand Society of Animal Production, 1991)
The effectiveness of hand combing, machine combing and body stocking covers relative to shearing were compared as methods of harvesting cashmere. Cashmere does were shorn on 4 August and combed on 4 August, 29 August and 3 October. Goats were covered and shorn on one side on 4 August and on the other on 3 October. Only 9 of the 40 goats retained their covers until 3 October. Machine combing was the least effective method of harvesting cashmere and produced a half fleece of 18

Rumen digest and other body measurements in relation to bloat susceptibility in cattle - Morris CA; Carruthers VR (Proceedings of the New Zealand Society of Animal Production, 1991)
Following the introduction of bucks on day 0 to isolated does there are peaks of oestrus on day 3 and day 7. While the day 3 peak is associated with low conception rates the day 7 peak is useful for partial synchrony for artificial insemination (AI). In this trial near Te Kuiti oestrous does were drafted off twice daily, starting day 5, following buck introduction. Those drafted in the evening were artificially inseminated laparoscopically with frozen- thawed semen the next morning and those drafted in the morning were artificially inseminated in the afternoon. On two farms the proportion of 207 and 123 mature does artificially inseminated on day 7-8 (day0=April 11) were 55% and 74% respectively, on day 6-10 inclusive 87% and 94% were artificially inseminated. On farm 1 on day 7-8 and day 6- 10 only 25% and 28% of 205 two tooths were artificially inseminated, in contrast on farm 2 74% and 84% of 70 two tooths were artificially inseminated. The farm 1 two tooths were 3.6 kg lighter than those on farm 2. CIDR-PMSG synchronised does from farm 1 (48 mature and 33 two tooth) were AIed on-time on days 6 and 10. There was no significant difference between the pregnancy rates of the CIDR synchronised (60%) and the buck induced does (56%). There were additive effects of type of oestrus induction and live weight on the % multiple pregnant. At 20 kg live weight the predictions of the % multiple pregnant were buck effect 11%, CIDR-PMSG 26%, and at 30 kg live weight 51% and 75% respectively.

Screening herds for cows with a history of twin calving - Morris CA (Proceedings of the New Zealand Society of Animal Production, 1991)
A monoclonal antibody to oestron sulphate (ES) was generated, and used in the development of a radioimmunoassay to measure ES concentrations in whole milk of cows. The mean

Secretion of insulin-like growth factor I and II from blood into milk of lactating goats - Prosser CG; Fleet IR; Davis AJ; Heap RB (Proceedings of the New Zealand Society of Animal Production, 1991)
No abstract supplied

The selection and breeding of Merino sheep for footrot resistance - Paterson R; Paterson H (Proceedings of the New Zealand Society of Animal Production, 1991)
An efficient farm AI system for sheep requires ready identification of, and access to, oestrus ewes. It is well known that ewes in oestrus seek out and remain near rams. The present experiment evaluated a variety of systems for trapping oestrus ewes attracted to two decoy rams. These systems included traps with one or two entrances, and traps sited 1.5 or 6 m from the rams. In each trial, 13 to 16 ewes in a flock of 45 mixed age and mixed breed sheep were artificially induced into oestrus and the proportions of oestrus ewes entering the trap was recorded. In addition, the trapping rate in a flock of naturally cycling 1

Selection for lean and against fat in sheep - Clarke JN; Rae AL (Proceedings of the New Zealand Society of Animal Production, 1991)
A model quantifying outputs of carcass from pasture inputs was used to study factors affecting biological efficiency (BE) of finishing beef from 6 months to slaughter. Two factors which determined biological efficiency (BE, kg carcass gain/ha/yr) on pasture were pasture utilisation and animal conversion efficiency. Effects of stocking rate, length of finishing period (1 v 2 years), mature size and maintenance efficiency of beasts on BE and its components were studied. Stocking rate was the major factor affecting utilisation rate however more lighter (eg. 12% more 750 kg than 900 kg mature sized) cattle need to be run to achieve equivalent pasture utilisation. Nine percent less cattle can be run in a 2 year system. Average conversion efficiency was 40% lower from finishing at 2 years than 1 year. An increase in mature size from 750 to 900 kg increased animal conversion by 14%. A 20% decrease in maintenance requirements increased animal conversion by 10%. Constraints to produce specified carcass weights further favoured BE with high mature weight beasts, particularly at intermediate carcass weights (250 kg). Breeding cattle for high mature size appears the best way of improving the cattle available for finishing.

Selection for resistance to parasites in sheep - Parker AGH (Proceedings of the New Zealand Society of Animal Production, 1991)
A milk replacer containing 40% non-milk constituents (V) was compared with a proprietary milk replacer (M) in two calf-rearing systems (H and R) using calves at pasture. Forty-eight, four week old Friesian calves were allocated to one of four treatments (in two replicates) and offered reconstituted milk replacers (140 g/l) : MH and VH, 81 daily for 3 weeks plus ad lib meal for two weeks; MR and VR, 41 daily for 5 weeks. Replacer M gave significantly (P<0.01) greater liveweight gains over the first 3 weeks for calves in treatment H but not in R. Treatment H calves showed a temporary growth check following weaning and again following the termination of meal feeding. Treatment R calves showed a progressive increase in daily rates of gain during the experiment. By 5-6 months of age the mean body weights of calves in all four groups were similar indicating that there were no adverse carry-over effects of replacer V, or the system of feeding. Significant savings in the cost of calf rearing are therefore possible.

The sexual behaviour of alpacas imported to New Zealand from Chile - Pollard JC; Moore GH; Littlejohn RP (Proceedings of the New Zealand Society of Animal Production, 1991)
FSH concentrations were examined in 6 FecB FecB (BB) ewe, 3 BB ram and 5 Fec+Fec+ (++) ram full-sibling pairs of Booroola Merino x Romney lambs between 2 and 20 weeks of age. The purpose of this study was to compare variation in FSH profiles within and between prepubertal full-sibling pairs of Booroola ewe and ram lambs, to evaluate their usefulness as control-treatment pairs in endocrinological studies. In ewe lambs, FSH concentrations increased with liveweight and age to reach distinct peaks at 7-12 kg liveweight and at 3-9 weeks of age. Variation between pairs was significantly greater than within pairs for liveweight at all ages, FSH concentrations up to 9 weeks of age, and maximum FSH concentration, but not for age or liveweight at peak FSH. In ram lambs, FSH concentrations were lower than in ewes but followed a similar pattern, with FSH peaks at 12-17 kg liveweight and 5-10 weeks of age. The geometric mean maximum FSH concentrations were 1.44 and 0.81 (LSR 1.78) ng/ml for BB and ++ groups respectively (P<0.05). Between- pair variation was significantly greater than within-pair variation for birth weight, liveweight to 7 weeks of age, peak FSH, and age at peak FSH. Mean FSH concentration and liveweight showed no relationship within or between ram pairs, or between ewe pairs, but the heavier sibling within all six ewe pairs had the higher FSH concentration (P<0.05) most samples up to 7 weeks of age, but not thereafter. The reduced variation in gonadotrophin concentrations within compared with between full-sibling pairs suggests they have considerable value as control-treatment animals in endocrine studies on prepubertal developments.

Sheep map: The New Zealand programme to map the sheep genome - Hill DF; Broad TE (Proceedings of the New Zealand Society of Animal Production, 1991)
A series of four trials, each involving 1200 ewes have been conducted over the period 1986 to 1990. Ewes have been treated with various synchronisation treatments and the time to onset of oestrus monitored each month of the year. Results indicate that while overall mean values for each year don't differ, there were significant seasonal effects within years with the interval to onset being shorter during the breeding season. However, the maximum difference between monthly means in any one year varied from 27 h to 17 h. Significant effects of synchronisation device were seen with ewes treated with sponges having a longer (+ 8 h) interval to onset than ewes treated with CIDR devices. While effects of ewe age and ewe liveweight were seen in some trials no consistent trend was identified. On most occasions significant interactions with month of year indicated inconsistency of effect within any one trial. The recorded variation in interval from device removal to onset of oestrus is in agreement with that reported between flock in the field. This variation is sufficient to effect conception rates to artificial insemination performed on a time basis and evaluation of contributing factors is required for the development of protocols for this activity.

Short term intake of Friesian heifers grazing three pasture species - Elliott AW; Hughes TP (Proceedings of the New Zealand Society of Animal Production, 1991)
Objective measures of muscularity were calculated for 1602 Romney and Romney-cross carcasses which were the progeny of 102 sires. Muscularity was defined as a measure of muscle thickness relative to carcass length. Phenotypic and genetic parameters were calculated from REML estimates of variance and covariance components. Different measures of muscularity had genetic correlations with one another between .48 and .84 and phenotypic correlations between .30 and .62. Measures of muscularity and high heritability (.40 to .68), positive genetic correlations with weight of carcass lean (.32 to .53) and carcass weight (.08 to .32) and negative genetic correlations with carcass fat (-.06 to -.33), and carcass length (-.11 to -.30). Single trait selection on muscularity was expected to result in increased lean and decreased fat. Selection on some of the muscularity measures was expected to result in increased subcutaneous fat. When the breeding objective gave positive emphasis to lean weight and negative emphasis to fat weight and the selection criteria were carcass weight and a muscularity measure, the muscularity measure that gave the greatest economic response to selection was that which used the longissimum muscle width (A) as a measure of muscle thickness.

A simplified MOET technique for Merino ewes carrying a double copy of the Booroola FecB gene - Shackell GH; Isaacs KL (Proceedings of the New Zealand Society of Animal Production, 1991)
Two trials were conducted to determine the effect of different oestrous synchronisation regimens on oestrous behaviour, timing of ovulation and fertility of fallow deer. In Trial 1, 59 mature does were allocated to 6 treatment groups (n+9-10 per group). Does in Groups 1, 2 and 3 each received an i.m. injection of an analogue of prostaglandin F2alpha (PG; 500 ug cloprostenol) on Day 13 of a synchronised oestrous cycle. Animals in Group 2 and 3 also received 50 or 100 IU PMSG respectively at the time of PG administration. Does assigned to Groups 4, 5 and 6 each received an intravaginal CIDR device for 14 days with animals in Group 5 and 6 also receiving 50 or 100 IU PMSG respectively, at the time of CIDR device withdrawal. Incidence of oestrus was higher following treatment with CIDR devices than with PG (29/30 vs 12/29, P<0.001). PMSG induced earlier onset of oestrus (34.6

Superovulation in ewes: are follicle numbers a useful predictor of ovulation rate? - McMillan WH; Hall DRH (Proceedings of the New Zealand Society of Animal Production, 1991)
The grazing behaviour of mixed age cashmere producing does was recorded on pasture dominated hill country at six physiological stages; post-weaning, pre-mating, early pregnancy, late pregnancy, early lactation and mid lactation. Observations were conducted from sunrise to sunset on three consecutive days at each physiological stage. Activity, land slope, time and position of focal animals were recorded. Flock position over the study site was also registered. At each physiological stage grazing was the predominant activity (34-63% of the time observed). The major grazing period occurred during the afternoon. Grazing occurred predominantly on steep and easy slopes (>70% of the time observed). Pasture height influenced the goats preference for the slope grazed. The does travelled in a regular pattern around the study site. This pattern was less distinct when the does had kids at foot. Activities observed during late pregnancy differed considerably from activities observed at other physiological stages. Some of these differences included more time spent standing and no distinct afternoon grazing period. Rain was the main event to interrupt grazing and initiate a change in the movement pattern of the does.

The time-course of milk yield and hormonal responses following growth hormone injections in hourly-milked goats - Davis SR; Hodgkinson SC; Farr VC (Proceedings of the New Zealand Society of Animal Production, 1991)
No abstract supplied

The timing of oestrus, LH surge and ovulation in ewes following synchronisation with MAP sponges FGA sponges or CIDR's - Shackell GH (Proceedings of the New Zealand Society of Animal Production, 1991)
As part of a programme to increase the number of homozygous (FecB FecB) replacements available in the Booroola Merino flock at the Tara Hills Research Station a MOET technique was utilised. Because ewes of BB genotype are difficult to superovulate, with predictable results, using conventional treatment regimes, a simplified programme aimed at enhancing the natural ovulation rate was used. Thirty eight ewes were treated for 10-11 days with intravaginal sponges. The ewes were then injected with 500 iu of PMSG on day 15 after sponge withdrawal and joined with entire rams for 5 days. Sixty six percent of ewes were marked by the ram and the mean ovulation rate of these was 8.3 (range 5- 18). Embryo recovery rate was 93.4% following retrograde flushing of the fallopian tubes. Fertilisation rate was 68% and 5.3 embryos were transferred per donor operated (range 0.-11). The ewes were remated and lambed naturally. By using a combination of MOET and remating, 24 donor ewes produced a mean of 3.3 lambs weaned compared to 1.4 lambs weaned by their naturally mated flock mates.

The use of dinucleotide repeats or microsatellites as genetic markers in domestic animals - Crawford AM; Buchanan FC; Swarbrick PA (Proceedings of the New Zealand Society of Animal Production, 1991)
Progesterone releasing devices are used to induce and synchronise oestrus in ewes and to provide supplementary progesterone post-mating to increase embryo survival. Because of its physical characteristics the Type-G CIDR device can be washed and re-used. Two trials each involving 1200 ewes were conducted. CIDR devices previously used for 14 days were evaluated in comparison to unused devices for their efficacy in; (1) induction and synchronisation of oestrus (50 ewes were treated with either new or used devices each month of the year with 400 I.U. PMSG given at device removal and the onset of oestrus and pregnancy monitored) or (ii) treatment post-mating (new, used or no devices were reinstated into groups of 33 ewes on Day 6 after a synchronised mating each month of the year. Pregnancy and lambing rates were monitored). Fewer ewes exhibited oestrus after treatment with the used CIDR devices and fewer became pregnant in Trial 1. There was no effect of post-mating treatment on pregnancy rate in Trial 2 but such treatment reduced the proportion of ewes have multiple births. Monthly variations in response were seen in both trials.

The use of fine and coarse bucks and G4 does for breeding for cashgora production - Paterson DJ; Litherland AJ; Newman S-AN; Edmonds DK (Proceedings of the New Zealand Society of Animal Production, 1991)
Stocking rates for maximum production and economic performance of Holstein-Friesians and Jerseys were predicted by calculating response curves from the regression equations of stocking rate on cow performance. Holstein-Friesians produced higher yields, gross milk incomes and net incomes per cow while Jerseys produced higher milkfat and protein yields, gross milk incomes and net incomes per ha when both breeds were stocked at the same liveweight or for maximum production or optimum economic performance. Maximum net income based on 1990/91 costs and prices occurred at 3.0 and 3.7 cows/ha for Holstein-Friesians and Jerseys respectively. At these stocking rates net income for Jerseys was 5% higher than for Holstein-Friesians.

The use of full-sibling pairs to measure plasma FSH concentrations in Booroola ewe and ram lambs - Isaacs KL; McNatty KP; Littlejohn RP (Proceedings of the New Zealand Society of Animal Production, 1991)
Forty-eight yearling Holstein-Friesian steers were assigned to three diets (Panicum virgatum (P) var. Cave-in-rock, Dactylis glomerata (D) var. Hallmark and Medicago sativa (M) var. Waterman Loomis 316) fed at two levels of intake (low (L) 65g DM kg-1 liveweight -0.75 day -1 or high (H) 90 g DM kg -1 liveweight -0.75 day -1) during a 6 month growth study. At the conclusion of the study animals were stunned, exsanguinated and promptly eviscerated and the rumen quickly emptied of its contents and subsequently weighed. Upon slaughter, rumen tissue samples were acquired from the ventral sac and placed in oxygenated M199 media. Mucosa and muscularis weights were determined along with their total 02 consumption, ouabain-senitive- (OSO2) and ouabain-insensitive-(OIO2) respiration. Tissue oxygen consumption was determined in vitro using a YSI Clark style electrode. Total, Mucosa and muscularis weights were greater (16.9-43.5%) with H and tended to be affected by diet (P<0.10). On a tissue basis, rumen muscle O2 consumption was not affected by treatment but mucosal OSO2 and percent inhibition of O2 consumption by ouabain were higher (6.9-94%) with Medicago. Total rumen O2, OSO2 and OIO2 consumption were higher (8.6-80.5%) in H (P<0.05) and diet affected OSO2. Rumen muscle total O2 consumption was greatest (3.51 ul 02/mg/hr) for D and altered by level of intake (P<0.03). Mucosal OSO2 and OIO2 were greater with H (P<0.04 and P<0.07, respectively). Total rumen O2 consumption is dominated by organ size rather than changes in weight specific O2 consumption. Therefore, at high forage intakes part of the decrease in the efficiency of ME utilisation is a consequence of increased heat production from the larger rumen.

The use of unfrozen semen for in vitro fertilisation of in vitro matured bovine oocytes - Seaton AD; Catt JW; Rhodes SL; McDonald MF; Welch RAS (Proceedings of the New Zealand Society of Animal Production, 1991)
Two herds with high (HS) or low (LS) susceptibility to pasture bloat have been selected divergently at Ruakura since 1972 using field bloat scores. The present paper continues studies on weights of rumen digesta, in 92 HS and 81 LS cull cattle experimentally slaughtered from 1985 to 1990. Traits recorded included pre-slaughter weight (PSW), hot carcass weight (HCW), the fresh weight, dry matter percentage (DM%) and dry weight of rumen digesta, weight of full abomasum and omasum, carcass composition, and weights of heart, liver, kidney and omental fat. In addition, pre-feeding and post-feeding girths at the last rib were obtained on 61 2- to 8-year old cows in mid-lactation, as a possible predictor of variation in rumen contents and in bloat susceptibility. The LS herd had a 10% greater PSW than the HS herd (P<0.001), and adjustments for body size were therefore made below to all traits from the abattoir except HCW and DM%. The fresh weights of digesta were similar in the two herds, but the DM% of digesta was 17% greater in LS than HS cattle (P<0.001). The weight of abomasum and omasum was 15% greater in LS than HS cattle (P<0.001), but there was no significant herd effect on fasting weight loss. Heart and kidney weights were 8 to 9% greater in LS than HS cattle. Ratios of rib girth to chest girth, in the absence of bloat, were not significantly different between herds at 1.172

A view of recent development on the effect of nutrition on ovulation rate (the flushing effect) with particular reference to research at Ruakura - Smith JF (Proceedings of the New Zealand Society of Animal Production, 1991)
The use of unfrozen, diluted bovine semen for in vitro fertilisation (IVF) was investigated. In vitro matured bovine oocytes were incubated with various (0.125 - 4.0 x 10 6/ml) concentrations of washed sperm. Penetration rates ranged from 21% at low sperm concentrations to 80-100% above 1 x 10 6 sperm/ml (P<0.01). Unfrozen sperm gave better penetration rates than frozen-thawed sperm. Oocytes were incubated with washed sperm (1 x 10 6/ml) in increasing dilutions of caprogen extender. Sperm penetration was significantly inhibited at dilutions of 10-fold or less (P<0.01). Oocytes were inseminated with washed sperm (1 x 10 6/ml) at various concentrations (0.50 ug/ml) of heparin. No significant differences were found.

The welfare of sheep during sea transport - Black H; Matthews LR; Bremner KJ (Proceedings of the New Zealand Society of Animal Production, 1991)
Sheep and their products contribute significantly to the New Zealand economy. A map of the sheep genome would accelerate the future genetic improvement of sheep by enabling loci for agriculturally and economically important traits to be identified and manipulated. Such a map would also contribute to the development of gene maps of cattle, goats and deer. The core of the New Zealand programme comprises two research groups (DSIR and MAF Technology) located at Palmerston North and Dunedin respectively.

Within-flock ranking of loose wool bulk and fibre diameter to predict wool lustre - Nicol JJ (Proceedings of the New Zealand Society of Animal Production, 1991)
Wiltshire Horn sheep exhibit an annual moult in spring and potentially provide a model for studies on the seasonality of wool growth. Twelve, 1 year old New Zealand Wiltshire ewes (Wiltshire Horn with some Poll Doreset in ancestry) were kept indoors under natural light and fed concentrates and hay. The sheep were cored for extent of fleece shedding every 2 weeks and skin sampled monthly for histological determination of primary and secondary follicle activity. Follicle activity reached a peak in summer and autumn (January to April) with low activity over winter (May to August) resulting in partial or entire shedding of the fleece in spring and early summer (September to December). There was evidence of a subsidiary shedding cycle in the primary follicles in early summer. Seasonal follicle activity was higher and longer in duration than previously recorded in British Wiltshire Horn ewes maintained on pasture. Four sheep with highly seasonal follicle activity cycles were identified as suitable for further studies on the endocrine control of wool growth. Such sheep can be selected from skin samples collected in June, July and August when follicle activity is at a seasonal minimum.

Wool growth in autumn and spring lambing ewes - Reid TC; Sumner RMW (Proceedings of the New Zealand Society of Animal Production, 1991)
Four trials in early to mid lactation investigated the effect of supplementation with sodium bicarbonate on milk production from cows grazing pasture. In Trial 1, 3 groups of 14 cows received 0, 100 g or 200 g NaHCO3/cow/day for 28 days. Trial 2 assessed whether any effects of sodium carbonate were due to sodium by comparing no supplement, 200 g NaHCO3/cow/day and 140 g NaC1 with three groups of 20 cows for 28 days. In both trials treatments were administered by drenching at each milking. Trial 3 assessed the importance of method of administration. Treatments of no supplement, 100 g NaHCO3/cow/day by drenching at the morning milking, or 100 g NaHCO3/cow/day in the drinking water were administered to 3 groups of 20 cows, during three 21 day periods according to a latin square design. Trial 4 compared rates of 0, 50, and 100 g NaHCO3 via drinking water with 3 groups of 18 cows for 21 days. In Trial 1 milk yield and protein yield were significantly reduced (P<0.10) by drenching 200g NaHCO3/day, compared to the control cows (14.,7 vs 15.3 kg milk/cow/day). The lower dose rate did not affect milk yield or composition. In Trials 2 and 4, none of the treatments significantly affected milk solid yields. Milk, protein and lactose yields from cows on the trough treatment were higher than those for control and drenched cows in Trial 3. Plasma magnesium was lower in drenched cows than in control or trough treatment cows.

Wool sulphur concentration in fleeceweight-selected and control Romney hoggets - Sun YX; Koolaard JP; Blair HT; Lee J; McCutcheon SN (Proceedings of the New Zealand Society of Animal Production, 1991)
Dairy and beef cows (n=349) which had calved at least two sets of twins were identified in farmers' herds in 1982-85. Their calving performance is summarised here, and an experimental herd was founded from a sample of them. The calvings of 11 high twinning-rate dairy herds identified from this publicity are also summarised. Repeat-twinning cows were from factory-supply dairy herds (66%), town-supply dairy herds (10%), beef herds (21%) and house cows (2%). The twin calving rate in factory-supply survey herds with Friesians was 2.6%, greater than the national average. There were, on average, 2.44 twin or triplet sets per cow. Of all the multiple births, 1.3% were triplet sets. Data on sex ratios of calves from the twinning cows suggested that probably all their twins were the result of multiple ovulations. Perinatal calf survival rates averaged 86%, with 80% of sets having both calves surviving; 21% of twin calvings were associated with a retained placenta, and 18% of twin calvings were assisted. Mean ages of cows at first and later twin calvings were also summarised. The 11 'elite' herds averaged a 4.1% twin calving rate (21 000 records), with 16% of cows calving at least one set of twins. Subsequent twin calving frequencies were summarised. The 69 foundation experimental cows averaged 2.39 twin sets and a 50% twin calving rate/year at purchase, and subsequently (1983-89) a twin calving rate of 10.3% (18 sets/174 calvings) compared with controls at 0.8% (1/121).

Absorption of DNA to the sperm of rams, bulls and fallow bucks - Peterson AJ; Schofield KM; McLaughlin RR (Proceedings of the New Zealand Society of Animal Production, 1990)
The algorithm for a Fortran program which simulates growth of a lamb is presented. The basis of the algorithm is the theory of growth and feed intake by Emmans. The advantages of the current algorithm are its simplicity, the few generalised equations and its easy use at any stage of the growth curve.

Animal industries in the 21st century - conclusions and challenges - Wallace RD (Proceedings of the New Zealand Society of Animal Production, 1990)
Bisected embryos not only create identical twins, but can also improve the efficiency of embryo transfer. We report here our experiences in applying the technique to sheep MOET programmes. Our basic technique involves holding a Day 5-6 embryo by negative pressure on a holding pipette and tearing the zona pellucida using 2 needles. A razor blade fragment is used to bisect the embryo and if required, a suction pipette manipulates demi-embryos into suitably prepared host zonae. In a preliminary study bisected embryos were examined for development during 24-48 h culture. Bisection in Ca2+, Mg2+-free media had no effect on viability. Naked demi-embryos blastulated more readily than those which were zona-enclosed and later stages tended to be the most viable, with morulae showing particularly poor development. This was supported by transfer data, where 11% of bisected late morulae, 50% of early blastocysts and 74% of blastocysts resulted in lambs. In comparison, 40% of control (unbisected) embryos lambed. Transfer of zona-enclosed demi-embryos tended to yield more lambs per original embryo (67%) than naked demi-embryos (43%). When the technique was applied to early blastocysts and blastocysts during 3 exotic sheep multiplication programmes in 1988, 47% and 55%, 100% and 39%, 73% and 47% of bisected and control embryos resulted in lambs respectively. Survival to lambing of dehydrated late morulae, bisected and subsequently enclosed in zonae, was similar to untreated control embryos (73% VS 59%) and greater than for naked embryos (36%). Our experiences indicate that bisected early blastocysts and blastocysts can increase the number of offspring in a MOET programme. However, since few blastocysts are available for bisection, and survival of demi- embryos is variable, we do not routinely use the technique.

Animal industries into the 21st century: a wool perspective - Wiggins LK (Proceedings of the New Zealand Society of Animal Production, 1990)
The MAFTech Sire Referencing Scheme is a national programme to evaluate rams, via progeny testing, throughout New Zealand. Phenotypic effects are reduced by using "Link sires" to make comparisons between properties valid. To enable link sires to be used over large numbers of animals in diverse locations, extensive use is made of Artificial Insemination (AI). Data from over 3,000 ewes mated by AI during the 1989 breeding season are presented. Various factors and their interactions were examined by fitting a generalised linear model with binomial distribution. The model showed that: the non-return rate from cervical insemination with chilled semen was 61% for ewes which had been treated with CIDRs and 62% (SED 3.4) for naturally cycling ewes; for frozen/thawed semen inseminate by the intrauterine route the corresponding rates were 70% and 40% (SED 7.0). In ewes treated with CIDRs the non-return rate was lower for cervical compared to intrauterine in semination (61% vs 70% SED 4.0). Ewes which were in oestrus more than 24 hours before insemination had a non-return rate of 58% compared to 63% (SED 2.6) for ewes which were in oestrus between 24 and 17 hours before AI and 71% (SED 3.1) when oestrus occurred less than 17 hours before AI. There was no evidence of an interaction between inseminated increased. (Coefficient for logit regression 0.14 se 0.064). Technicians success rate ranged from 51% to 76% non returns, when adjusted for other factors. Although differences among the 31 sires did not contribute significantly to this model, predicted non-return rates when sire was added to the model ranged from 39% to 86%. There was no evidence that ewe breed influenced non-return rate.

Animal industries of the 21st century : a meat industry viewpoint - Thompson G (Proceedings of the New Zealand Society of Animal Production, 1990)
The use of modern technology is having a major effect on the structure of ram-breeding in NZ. The uptake of sire referencing schemes (SRS) and artificial insemination (AI) is having an impact on the whole structure of breeding groups and the industry. The role of traditional group breeding schemes is being questioned by the industry. The structure of New Zealand dairy breeding underwent a period of change with the introduction of AI and sire proving in the 1950's. Some aspects of these changes are relevant to the sheep industry. The decrease in the size of the national flock, increasing ram ratios and the use of AI will all impact on the industry over the next 5-10 years. The industry is responding to the new environment with groups like the NZ Romney Development Group and the Perendale Genetic Development Group re-evaluating their objectives and making major changes to their structures. This paper looks at these changes and the likely effect on the sheep breeding industry.

Animal production and the 'greenhouse gases' - Reid CSW (Proceedings of the New Zealand Society of Animal Production, 1990)
No abstract supplied

Animal production in the future - a New Zealand response - Fennessy PF (Proceedings of the New Zealand Society of Animal Production, 1990)
As a pre-requisite to examine the possibility of using spermatozoa as a vector for the incorporation of foreign DNA into livestock, the ability of sperm from sheep, fallow deer and cattle to bind exogenous DNA was examined. The DNA was obtained from the plasmid pMK1 linearised with EcORIXhoI and end-labelled with 32P. Fresh sperm from all species bound DNA with maximum binding occurring after 1hr of incubation. Frozen sperm bound less DNA and formaldehyde treated sperm did not bind. Seminal plasma inhibited binding as did heparin and also high divalent cation concentrations. Capacitated ram sperm bound more than uncapacitated (64% vs 40%) and uterine fluids from sheep two-days post-estrus did not interfere with DNA binding to the capacitated ram sperm. Increasing the concentration of washed capacitated ram sperm from 1 x 10 6/ml to 30 x 10 6/ml and with a DNA concentration of 0.25 mg/ml decreased the number of molecules of DNA bound from 38,000 to 1,600. There was wide variation among rams in the percentage of DNA bound after 1hr incubation, ranging from 15-80% (n=7). These results suggest that this procedure may be a possible method for the incorporation of foreign DNA into livestock by intrauterine insemination.

Animal researchers and farmers must take heed of changing attitudes toward animal welfare and the protection of the environment - Sutton J (Proceedings of the New Zealand Society of Animal Production, 1990)
Genetic variation in the beta chain of haemoglobin (HBB) and the beta chain of follicle stimulating hormone (FSHB) was analysed for linkage with the Booroola F gene in large half-sib families or a backcross Romney x Booroola Merino flock where the Booroola F gene was segregating. The half-sib families were highly informative at the HBB locus with 6 of 7 sires heterozygous (AB) for the two alleles. Recombination between the HBB and F gene loci were observed in all six families and the F gene was significantly excluded from within 15 centimorgans (cM) of HBB. A cDNA probe for the FSHB gene detected an insertion/deletion polymorphism close to exon 3 of the gene. Recombination was observed in 4 pedigrees in the half-sib families and the backcross flock and the F gene was excluded from within 5 cM of the FSHB gene.

Biochemical mechanisms related to overfatness in lambs - Payne E (Proceedings of the New Zealand Society of Animal Production, 1990)
A mechanistic model was used to measure the impact of changes in climate (temperature, rainfall and solar radiation) and a 75% increase in the concentration of atmospheric carbon dioxide on pasture and animal production on eight representative New Zealand lowland farming systems. The climate changes increased annual pasture dry matter production per hectare by 10-30%, assuming no changes in pasture composition. A 75% increase in CO2 concentration increased pasture production by around 40%. Together, climate change and increased CO2 concentration increased yields by 50-77%. In all cases, the seasonal distribution of pasture production was not greatly affected. Both climate change and increased CO2 concentration individually increased annual milk production per hectare by around 24%, lamb meat and beef by around 30% and wool by around 22%, under the constant farm management systems selected. The increases in production were mainly due to increases in stocking rate resulting from the increased pasture production, but increased conservation and feeding out of hay were required. The model predicted an increase in lamb growth rates. Milk, meat and wool production was higher under climate change than under increased CO2 concentration in Southland, but the opposite was true in northern New Zealand. The combined effect of climate change and increased CO2 concentration was greater, with potential increases over the two scenarios averaging 52% for milk, 57% for lamb and beef and 46% for wool.

The Booroola F gene is excluded from close genetic linkage with either the haemoglobin Beta or follicle stimulating hormone Beta loci - Montgomery GW; Tate ML; Sise JA; Hill DF (Proceedings of the New Zealand Society of Animal Production, 1990)
No abstract supplied

Carcass and meat quality in possums (Trichosurus vulpecula) - Hogg BW; Catcheside LM; Mercer GJK; Pearson AJ; Ashby MG (Proceedings of the New Zealand Society of Animal Production, 1990)
Production data were collected over 4 years from a flock of 600 mixed-age Romney, Coopworth and Perendale ewes. There were approximately equal numbers of each breed. Ewes within breeds and age groups were randomly allocated to be shorn either once-yearly in January, once-yearly in July or twice-yearly in January and July. All ewes were grazed as a single mob throughout the year, except over mating when they were divided into breed groups and joined with rams of their own breed. The twice-yearly shorn ewes gave birth to, and weaned, heavier lambs and grew more total clean wool than the 2-once-yearly shorn groups which were similar. Shearing treatment did not affect ewe live weight, aspects of lamb production other than birth weight and weaning weight or total greasy wool production. Incidence of casting was less than 1%. Net wool returns from the ewes shorn once-yearly in July exceeded that of the ewes shorn twice-yearly which exceeded that of the ewes shorn once-yearly in January.

Carcass composition of autumn- and spring-born lambs - Reid TC; Kirton AH; McQueen IPM (Proceedings of the New Zealand Society of Animal Production, 1990)
The sexual behaviour of alpacas joined under a selective breeding programme was recorded to assess performance and to examine ways of providing optimal conditions for mating. Groups of 4 females and 1 male were joined in paddocks for 5 days (3 groups) or in pens for 3.5 hours on 2 consecutive mornings (3 groups). Sexual activity was more variable in paddocks compared with pens, and more females were mated in pens. Duration of copulation was longer in pens that in paddocks, and for first compared with subsequent matings. Within pens, sexual activity was more intense during the first hour following joining than for the subsequent 2.5 hours, on Day 1 than on Day 2, and differed between groups. Females became more receptive later in the mating sessions. The study indicated that pen mating using small single-sire groups, over short periods, was a suitable method of breeding alpacas.

The challenge of endoparasitism: developments in the control of nematode infections of sheep - Anderson N (Proceedings of the New Zealand Society of Animal Production, 1990)
Twelve Romney wether lambs, average weight 28kg, were randomly divided into two groups, namely an untreated control and an Fe treated group. All animals were grazed together on a ryegrass/white clover pasture for 12 weeks. The Fe intake of the control animals was estimated to be 247 mg/day while that for the treated animals was 827 mg/day with the extra Fe (FeSO4.7H2O) given orally in a gelatin capsule. Increasing the Fe intake had no effect on DM intake or growth rates but significantly (P<0.05) increased the Fe content of the lungs, spleen and digestive tract. No other changes in Fe concentrations were found in the other soft tissues or bone. There was a marked decrease [50%] in the Cu content of the liver (a major storage organ for Cu) when the Fe treated lambs were compared with the control animals. The fact that a moderate increase in the intake of Fe can markedly reduce the Cu status of lambs may be a more important finding than has been previously realised.

Changes in the fur quality of caged brushtail possums (Trichosurus vulpecula) maintained in captivity - Pearson AJ; Ashby MG; MacGibbon RJ (Proceedings of the New Zealand Society of Animal Production, 1990)
This paper backgrounds important features which are likely to influence the future of animal production in New Zealand. They include the importance of being in the quality market, consumer attitudes, market access and environmental/welfare concerns. In view of the changing perceptions about animal production, the place of technology in on-farm production needs to be carefully considered. Technologies can be defined as 'soft' or 'hard', the latter being those which introduce major perturbations into the system. The impact on the whole system is particularly important. The possibilities for genetic improvement are considered in detail. The soft technology approach is favoured in that it works with existing genetic variation but uses new technology approach is concerned mainly with the development of transgenic animals. Overall, developments in technology have much to contribute to the animal industries in New Zealand, but the importance of off-farm issues such as marketing, market access and product development are particularly critical. There is a need to take a broad view of animal production in considering the future.

Characterisation of the insulin status of lambs and consequences for carcass composition - Willis JA; Bickerstaffe R; Munro JM; O'Connell D (Proceedings of the New Zealand Society of Animal Production, 1990)
As part of the study into the mechanism by which nutrition influences ovulation rate two trials have been conducted to examine the effect of protein intake on the negative feedback of oestradiol-17Beta (E17Beta) on plasma FSH levels. In Trial 1 three groups of ovariectomised ewes (n=8) fed on a low protein (LP 11%, 10 MJ ME) diet were treated with silastic implants of E17Beta. Four days after implant insertion one group was changed to a high protein (HP 22%) diet while another was treated orally for 10 days with phenobarbital (1 g/d). The E17Beta implants were removed 6 days after treatment started. In Trial 2 groups of ewes (n=6) were given either full (HE) or 1/2 size (LE) implants for 5 days. All ewes were fed on a LP diet but 2 groups were infused abomasally with 100g/d of protein (HP) commencing 3 days before implant. FSH levels were monitored 4 x d throughout both trials and expressed as a percentage of pre-treatment values. In Trial 1 FSH levels were 33% on day 11 after implant with no treatment difference. However after implant removal the values for the LP ewes returned to 100% by day 17 while for the HP and phenobarbital group values remained at 33%. In Trial 2 the levels 4 days after implant insertion were 37%, and 48% for the HE and LE ewes. Again protein treatment delayed recovery following implant removal. These results do not support the hypothesis that the increased ovulation rate following protein supplementation is due to a reduction in negative steroid feedback on FSH levels.

Comparative nutrition of deer and goats, goats and sheep - Domingue BMF; Dellow DW; Wilson PR; Barry TN (Proceedings of the New Zealand Society of Animal Production, 1990)
No abstract supplied

Comparison of commercial gonadotrophins using bioassays - Henderson KM; Weaver A; Wards RL; Lun S; McNatty KP (Proceedings of the New Zealand Society of Animal Production, 1990)
The immune response of sheep to nematode parasites involves a cascade of events beginning with the recognition of nematode antigen, followed by stimulation of the immune system to elicit the appropriate cellular response at the gut mucosa and finally the release of products which promote the elimination of the parasite from the gut. These processes are examined and deficiencies in the knowledge are highlighted. The application of the knowledge of the sheeps' immune system to the identification of a marker for resistance and opportunities for the control of nematodes through manipulation of sheeps' responsiveness are discussed. The progress that has been achieved in the experimental breeding of sheep for nematode resistance is examined. The use of such valuable scientific resource flocks for studies which advance the understanding of the immunology of resistance is discussed.

Comparison of growth and carcass traits of ram lambs of three breeds from a flock screened for prolificacy and a Romney control flock - McEwan JC; Davis GH; Dodds KG; Fennessy PF; Clarke JN; Hishon M (Proceedings of the New Zealand Society of Animal Production, 1990)
This paper reviews the application of intraruminal chromium controlled release capsules (CRC, Captec (NZ) Ltd, Auckland) to the measurement of herbage intake in ruminants. The capsules are designed to provide for the linear release of Cr2O3 over c. 25 days in sheep and c. 20 days in cattle. Uniform release of Cr2O3 is achieved 2 to 3 days after oral administration of the CRC but steady state levels of Cr2O3 in the faeces are usually not achieved until day 7 or 8 in sheep and day 5 or 6 in cattle. Where cross-over or multiple feeding level experimental designs are applied, time should be allowed for Cr2O3 to adjust to a new steady state in the faeces before sampling for each new treatment. The period of time required varies from 3 to more than 5 days depending on the size of feed intake change. The continuous mode of marker release in the rumen reduces diurnal variation of Cr2O3 in the faeces and this allows rectal sampling regimens to be applied at different times of each sampling day. Sward sampling of faeces reduced disturbance of animal grazing to a minimal level since Cr2O3 is delivered by a single CRC application. The effects of level of feed intake and feed type on the rate of Cr2O3 release are usually small, but release rates may be up to 13% lower in rumen-fistulated than in non-fistulated animals and may differ for capsules of the same time applied to different ruminant species. Reduced animal handling, flexible faecal sampling times and lower labour requirements with CRC technology, compared to daily drenching of Cr2O3, enable the number of experimental animals to be increased. This improves the likelihood of detecting differences in mean intake between groups. Intakes of individual animals will not be reliably estimated with chromic oxide CRC until the digestibility of herbage consumed by individual animals can be measured more accurately.

Comparison of herbage intakes estimated from in vitro or alkane-based digestibilities - Dove H; Milne JA; Mayes RW (Proceedings of the New Zealand Society of Animal Production, 1990)
No abstract supplied

A computational model to predict lamb growth - Bell ST; Cropper MR; Poppi DP (Proceedings of the New Zealand Society of Animal Production, 1990)
Two trials were conducted to study factors which influenced the amount of progesterone (P4) remaining in a CIDR intravaginal device used for a treatment period of 15 days and the associated plasma P4 concentrations. In the first trial, the initial P4 content of these devices was varied from 0 to 2.67g P4. In the second trial, animals were treated with either one or three devices which had been moulded to contain the same amount of P4 (1.9g/device). Increasing the initial P4 content of a device increased plasma P4 concentrations, but at a diminishing rate so that devices containing 1.86g P4 maintained similar levels of plasma P4 to devices containing 2.67g P4 (2.48 vs 2.63 ng/ml). This was associated with a quadratic relationship in the residual P4 content in the used devices. Using three devices per animal trebled plasma P4 concentrations and did not alter residual P4 content. These results indicated that P4 release is influenced more by device characteristics than by animal variation.

Concentration of melatonin in plasma of goats treated with Regulin - Parry AL; Paterson DJ; Litherland AJ; Death AF; Staples LD (Proceedings of the New Zealand Society of Animal Production, 1990)
Sustained release of melatonin from implants or microcapsules administered in October induced cashmere growth during November to March in all ten, treated, cashmere-bearing goats. The mean maximum length of the cashmere in this induced fleece ranged from 12-55mm. Another cashmere growth cycle followed between autumn and winter. In contrast, nineteen control goats grew cashmere only during the autumn-winter period. Melatonin treatment increased total mean cashmere staple length by up to 65% for treated animals compared with controls. The onset of growth of the autumn fleece in the treated goats was delayed as also was the time when maximum length was achieved on shedding occurred. Melatonin treatment should permit the shearing of the autumn fleece to be delayed, thus reducing the risk of post-shearing losses during inclement weather in late winter.

Development and use of gene transfer in New Zealand - Bullock DW (Proceedings of the New Zealand Society of Animal Production, 1990)
A major factor in the reduction of growth in parasitized lambs is the depression in food intake by a mechanism not yet understood. Investigation of the pattern of eating has shown that parasitized lambs have a lower (35%) cumulative intake, especially within the first hour of feeding, which return to a control level on drenching. The importance of two factors which may moderate intake depression, the activity of ventromedial hypothalamus (VMH) and elevated cholecystokinin (CCK), were investigated. Four animals with intake depression (approximately 40% P<0.05) as a result of continuous infection with 4000 T.colubriformis per day for 12 weeks together with 4 control animals received, in a replicated latin square design 0, 1, 2 and 4ml i.v. of a compound (brotizolam) used to block the satiety effect at the VMH. Intake increased (P<0.05) within the first hour of feeding of both parasitized and control animals (approximately 2.6 and 1.9 times, respectively). Four similarly infected and 4 control lambs were given varying doses of a potent antagonist of peripheral CCK action without effect on food intake. These results suggest that depression of food intake in parasitized lambs appears to involve central satiety signals and not peripheral CCK.

Developments in artificial insemination and controlled breeding in dairy cattle and deer in New Zealand - Macmillan KL; Asher GW (Proceedings of the New Zealand Society of Animal Production, 1990)
A number of techniques for directly manipulating the mammalian germline have been established in the mouse. During the past five years these have been applied to domestic livestock but, so far, only pronuclear microinjection has proved successful. The considerable resources required and the low efficiency of the procedure are major limitations and, worldwide, relatively few laboratories have produced transgenic livestock. In applying rtransgenic technology to farm animals, a major effort has gone into the manipulation of growth. This is a complex trait and progress has been constrained by the inability to control the expression of transgenes in a precise manner, and by the lack of basic knowledge at the interface between molecular biology and physiology. By contrast, the production of biomedical proteins from transgenic animals involves the manipulation of a relatively simple trait, milk composition. So far, only relatively low levels of protein production have been reported for transgenic sheep. However, very high levels of expression of human a1-antitrypsin have been obtained in transgenic mice, demonstrating the feasibility for this application of transgenic animals.

Developments in domestic animal embryo manipulation technology which support the application of molecular biology to animal production - Tervit HR; Thompson JG; Peterson AJ (Proceedings of the New Zealand Society of Animal Production, 1990)
A simulation model for mixed infections of gastrointestinal nematodes in lambs was used to compare with a series of extended drenching programmes. The model output concurs with the results of field trials showing that preventive drenching will control parasites adequately except when autumn conditions are particularly favourable for development and migration of larvae onto pasture. The model suggests that the level of pasture contamination in spring will have a significant influence on parasite control throughout much of the year. A reduction in pasture contamination was simulated by the addition of a post-lambing ewe drench prior to the preventive lamb drenching programme. This gave better parasite control and increased production compared with extended drenching of lambs in the autumn. This is likely to be the result of reduced larval challenge. These model predictions will require validation in the field.

DNA profiling in sheep - Crawford AM; Buchanan FC (Proceedings of the New Zealand Society of Animal Production, 1990)
No abstract supplied

Effect of duodenal infusion of protein or amino acids on nitrogen retention of lambs consuming fresh herbage - Fraser DL; Hamilton BK; Poppi DP (Proceedings of the New Zealand Society of Animal Production, 1990)
The first two years of a breeding trial have shown that sires with slow clearance of glucose after a glucose tolerance test will produce progeny with similar slow clearance and leaner carcasses (Line 1), than progeny from sires with fast glucose clearance (Line 2). Six extreme animals from each Line were selected to study the biochemical mechanisms controlling the effects seen in the breeding trial. An euglycaemic clamp experiment involved infusing insulin at three levels, 0.63, 3.46 and 6.29 mU/kg liveweight 0.75/min, each for four hours. At the same time glucose was infused with adjustments to maintain plasma glucose at basal levels. The amount of glucose infused is a measure of the sensitivity of the peripheral tissues to insulin. Line 1 animals required significantly (P<0.05) more glucose to maintain euglycaemia during all three levels of insulin infusion. Because there were differences in basal plasma glucose (Line 1:71, Line 2:61 mg/100ml, P<0.05), glucose utilisation was corrected for basal glucose. Line 1 animals still had greater glucose utilization. Another measure of insulin sensitivity is the change in glucose utilization relative to the change in plasma insulin as insulin infusion increases. Line 1 animals had a significantly greater insulin sensitivity index than Line 2 animals (0.505 versus 0.193, P<0.01) for the change from level 1 to level 2. When corrected for differences in basal glucose, Line 1 animals were still significantly more sensitive to the increase in insulin (0.680 versus 0.346, P<0.01). Selecting animals for breeding by glucose tolerance produces sheep with differences in glucose utilization by peripheral tissues. These biochemical differences are important in partitioning nutrients for deposition of lean or fat tissue.

The effect of early exposure to facial eczema on ewe lifetime production - Moore RW; Sumner RMW; Dow BW (Proceedings of the New Zealand Society of Animal Production, 1990)
No abstract supplied

The effect of endoparasitism on host nutrition - the implications for nutrient manipulation - Poppi DP; Sykes AR; Dynes RA (Proceedings of the New Zealand Society of Animal Production, 1990)
Colostrum is an essential post-natal energy source. We have investigated the link between lamb serum immunoglobulin concentration and colostrum intake as a means of estimating lamb energy intake. Thirty previously unsuckled Coopworth and Corriedale lambs were bottle fed fresh colostrum at 60, 135, 210 or 285 ml/kg birth weight 24 hr in equal feeds at 2 or 4 hour intervals from birth to 30 hours after birth. IgG in serum was measured before first feeding and then at 8 hour intervals to 32 hours after first feeding by ZnSO4 turbidity. Prior to feeding mean serum IgG concentration of the lambs was 0.41

Effect of increasing Fe intake on the Fe and Cu content of tissues in grazing sheep - Grace ND; Lee J (Proceedings of the New Zealand Society of Animal Production, 1990)
The fleeces of 30,000 ewe hoggets from 12 Merino flocks were sampled and the mean fibre diameter and clean fleece weight were measured in 1987 and 1988 and the best were selected to establish a superfine joint venture (SFJV) flock of 307 breeding ewes. The breeding objective is to achieve mean fibre diameter below 17um in the adult fleece while maintaining fleece weight and live weight. Concomitantly, a random control flock (RC) of 101 ewes was constituted from the flocks screened. Both flocks are farmed on MAF Technology's high country station at Tara Hills, Omarama. The screened SFJV flock has significantly lower live weight (p<0.01), greasy fleece weight (p0.05), loose wool bulk (p<0.001) and mean fibre diameter by 2 um (p<0.001). Staple length (P<0.001), staple crimp (P<0.05) and yield (P<0.05) were significantly higher for the SFJV flock compared with the RC flock. Wool returns of SFJV flock were $81.78/hd and $107/hd vs $62.21/hd and $47.00/hd for RC flock in 1988 and 1989 shearing respectively

Effect of oestradiol implants and protein nutrition on plasma FSH levels in ovariectomised ewes - Smith JF; Cruickshank GJ; Payne E; Konlechner J; Parr J; McGowan LT; McLaughlin RR (Proceedings of the New Zealand Society of Animal Production, 1990)
The possible impact of developments in artificial insemination (AI), multiple ovulation and embryo transfer (MOET), sexed semen and embryos, cloning, physiological markers, genetic markers and transgenic livestock on rates of genetic change are reviewed and discussed. Previous theoretical predictions have exaggerated the potential increases in rates of genetic change available from MOET, particularly in small, closed MOET nucleus schemes. Sexing of semen and/or embryos has a relatively small effect on rates of genetic change, but sex control can potentially have a dramatic effect on the efficiency of farming systems. Developing techniques to produce large clone families in livestock will increase rates of genetic change, particularly through faster dissemination of superior genotypes to commercial populations. A cost-benefit analysis of some different strategies for increasing genetic change in the New Zealand dairy cattle population has identified that useful contributions could come from AI (by doubling current bull coverage) and from MOET and genetic and/or physiological markers. Equally important economic returns were identified from increasing the number of bull mothers continuously bred by AI. The impact of transgenic animals, gene mapping and genetic markers (linkage) on rates of genetic change is likely to take much longer (10- 20 years) than the reproductive techniques.

The effect of pre-mating feeding level and age on liveweight change on reproductive performance of cashmere does - Parry AL; Edmonds DK; Knight TW; Hamilton GJ (Proceedings of the New Zealand Society of Animal Production, 1990)
The results in this field over the last 10 years at Ruakura and relevant international data is reviewed. The nutrients involved have been defined and a likely mechanism of action indicated. Pasture allowance experiments indicated effects of pasture quality and a series of pellet feeding trials defined effects of both energy (linear) and protein (threshold) intakes. The threshold effect of protein was confirmed by the abomasal infusion of protein. Analyses of changes in blood concentrations of amino-acids indicated the involvement of the branched-chain amino-acids (BCAA) and this has been confirmed by an increased ovulation rate after intravenous infusion of BCAA. It is concluded that the static and dynamic liveweight and the immediate nutrient effects are the same response measured at different times. The rate at which the response develops is dependant on the type of feedstuff. Studies into the mechanism of action in both intact and ovariectomised ewes have ruled out effects on pituitary release of FSH either directly or via interference with negative feedback influences. This indicates that the effect is at the ovarian level and is mediated either by direct action of the BCAA or indirectly via a metabolic hormone.

Effect of shearing once-yearly in January, once-yearly in July or twice-yearly in January and July on ewe performance - Sumner RMW; Scott ML (Proceedings of the New Zealand Society of Animal Production, 1990)
The major challenges facing the sheep industry are improving animal performance, minimising disease, reducing labour, and being attuned to consumers' long term needs. Solutions will involve new technology in sheep breeding, biological disease control and novel approaches to reducing labour associated with sheep. Environmental, health and welfare issues are shaping up to be major consumer issues by the 21st century and production techniques will come under closer scrutiny in future.

The effects of nutrition oestradiol, phenobarbital and carbon tetrachloride on ovulation rate and plasma FSH in ewes - Payne E; Smith JF; Peterson AJ; McGowan LT; Cope BC; McLaughlin R (Proceedings of the New Zealand Society of Animal Production, 1990)
Recent advances in the genetic manipulation of animals have raised some familiar and some less familiar ethical issues. The obligation to safeguard the welfare of animals must be extended to include the production of transgenic animals, to ensure that the well-being of such "products" takes precedence over profitability. Human welfare must also be safeguarded especially in relation to the equitable distribution of the benefits from genetic engineering and the protection of the environment. The change in the relationship between human and non-human animals, exemplified in the patenting of genetically modified animals, has serious implications for the integrity of animal science.

Effects of varying the progesterone content of CIDR intravaginal devices and multiple CIDR treatments on plasma hormone concentrations and residual hormone content - Macmillan KL; Washburn SP; Henderson HV; Petch SF (Proceedings of the New Zealand Society of Animal Production, 1990)
No abstract supplied

Estimation of the pasture horizons grazed by cattle, sheep and goats during single and mixed grazing - Nicol AM; Collins HA (Proceedings of the New Zealand Society of Animal Production, 1990)
The nutritional treatment of lambs influences the extent of carcass fat deposition. Suckled lambs deposit more fat than weaned lambs with associated increases in plasma glucose and insulin levels. To investigate the mechanisms involved, groups of lambs with different insulin profiles were created, either nutritionally or by infusing insulin, and the effect on carcass composition determined. Border Leicester x Dorset lambs were either weaned at 5 weeks of age or remained suckling with access to grass. Twenty four lambs were slaughtered at 12 weeks of age, the remaining lambs were slaughtered at 23 weeks of age. A subset of both weaned and suckled lambs were treated with exogenous insulin from 5 weeks until slaughter. Insulin status was assessed by the glucose tolerance test and by the response of plasma glucose to injected insulin. The prolonged suckling of lambs increased carcass fatness and decreased carcass protein compared to early weaned lambs. Infusing insulin decreased carcass fatness and increased carcass protein. The alterations in carcass composition were associated with changes in the sensitivity of peripheral tissues to insulin.

Ethics and animal production - Campbell AV (Proceedings of the New Zealand Society of Animal Production, 1990)
Research has shown some dairy cows show temporary falls in plasma calcium concentration during the first six weeks of lactation. By monitoring plasma calcium concentrations in 58 dairy cows in 4 herds for 42 days postpartum it was found that 33% showed at least one episode of a fall in plasma calcium concentration to <1.9 mmol/l. The mean plasma calcium concentration of these cows during this period was 2.15 mmol/l compared to 2.60 mmol/l for those cows which maintained plasma calcium concentrations above 2.10 mmol/l for six weeks and 2.35 mmol/l for another group which maintained plasma calcium concentration above 1.9 mmol/l but not always above 2.1 mmol/l. These mean calcium concentrations differed significantly (P<0.001) among the three groups and between sampling days after calving. There was no significant association between herd and distribution of cows in each group and age of cow was not significantly correlated with plasma calcium concentration on days 7, 9, 19, 29 and 42 after calving or with the overall mean concentrations. Sub-clinical hypocalcaemia may commonly occur in early lactation and have significant effects on production and reproduction in dairy cows.

Experiences in the application of embryo bisection in sheep MOET programmes - Wells DG; Thompson JGE; Tervit HR; James RW; Udy GB (Proceedings of the New Zealand Society of Animal Production, 1990)
Hypervariable DNA probes can be used to detect a series of polymorphic markers that are stably inherited and potentially useful in genetic analysis. We have determined the amount of informative polymorphism that would be revealed by these probes if genetic crosses were to be created within and between flocks of Romney sheep selected for resistance and susceptibility to facial eczema.

Exploiting the physiology of growth - Buttery PJ; Dawson JM; Harper JMM (Proceedings of the New Zealand Society of Animal Production, 1990)
The response of ram lambs from the Massey university backfat selection lines to a urea load were measured in order to ascertain whether there were line effects on urea space and to evaluate relationships between urea space and empty body water content. Thirty- six 6-8 month-old ram lambs held in metabolism crates and fed lucerne chaff at 1.3 maintenance, were given 120mg urea/kg through jugular catheters. Plasma urea levels were measured in samples taken before and after the urea load. All animals were slaughtered within 7d of the urea challenge and total body water was determined. In contrast to previous studies, baseline plasma urea levels were not significantly higher in the high-backfat-line animals and were not related to carcass fat or water content. The increases in urea levels following the urea load were greater for the high backfat line at 15min, but not at subsequent sampling times. Clearance rates following the load did not differ between the lines. Correlations between empty body water and estimates of urea space were low, suggesting that this is not a useful means of obtaining body composition information for live sheep at this stage. Urea space estimated in several ways was significantly higher for the low backfat line group.

Facial eczema in Jersey cattle: heritability and correlation with production - Morris CA; Towers NR; Tempero HJ; Cox NR; Henderson HV (Proceedings of the New Zealand Society of Animal Production, 1990)
Fifty-eight possums (28 male, 30 female) were captured from the wild. Animals were grouped into ages of 1, 2-4 and 5+ years. Males were always heavier than females of the same age, while carcass weight increased significantly with age up to 5+ years. Age had a more pronounced effect on carcass composition and meat quality than sex. At all ages, and in both sexes, possums produced carcasses which were high in dissected lean (78-80%) and low in fat (0.8-2.6%). Their meat was very high in protein (24-26%) and low in fat (1.4-2.0%). Tenderometer results showed that all age groups produced meat which would be rated as acceptably tender.

Factors influencing the success of a large scale artificial insemination programme in sheep - Shackell GH; Kyle B; Littlejohn RP (Proceedings of the New Zealand Society of Animal Production, 1990)
Two experiments were conducted to compare PMSG injection to GnRH infusion for induction of breeding in anoestrous ewes. In Experiment One, sixteen Suffolk ewes were pre-treated for 14 days with 30 mg Cronolone sponges. At sponge removal half of the ewes received 0.125 ug/hr GnRH for 72 hours via subcutaneous osmotic pumps. The other half received a single injection of 750 iu PMSG. Plasma LH levels gradually increased and were sustained for 24 hours. Estrus, ovulation and corpus luteum function were expressed in half of the ewes treated with GnRH. All ewes treated with PMSG exhibited estrus, ovulated and formed functional corpora lutea. In Experiment Two, 24 ewes were divided into two groups and the same treatments as in Experiment One were applied. Fertile rams were introduced to all the ewes at the time of sponge removal. Estrus was detected in 75% of the GnRH treated ewes vs 100% in PMSG treated ewes. Lambing rates were 44% and 56% in GnRH and PMSG groups respectively. These results suggest that the induction of fertility using continuous infusion of GnRH is encouraging. However, other GnRH delivery systems should be investigated.

Feasibility of intensive artificial insemination programmes using natural oestrus subsequent to synchronisation with CIDR-G in Merino ewes - van Reenen GM (Proceedings of the New Zealand Society of Animal Production, 1990)
Genetic variation among 7 sheep breeds was investigated using 10 DNA probes. No significant differences were observed between Romneys, Coopworths and Perendales at any of the loci examined. Significant variation was observed between Romney related breeds and Merinos at several loci. At the haemoglobin locus (Hb), a probe which appears to detect alleles coding for HbA and/or HbB as classified by protein electrophoresis, failed to detect alleles in all samples. The missing allele appeared predominant in Texel DNA samples, but was also seen in Romneys, Coopworths and Merinos. A new allele was detected in Texel DNA with a probe coding for the Beta subunit of follicle-stimulating hormone (FSH-Beta). This allele was observed at a high frequency in the Texel population and may be Texel specific. Similarity of allele frequencies between the Gotlands and Finns at many loci suggests that these two breeds may be related. Texels and Merinos do not appear to be closely related to any of the breeds studied.

Fertility of anestrus ewes infused with gonadotropin releasing hormone or injected with pregnant mares' serum gonadotropin - Hamra AH; Wheaton JE; Marcek JM (Proceedings of the New Zealand Society of Animal Production, 1990)
No abstract supplied

Fifty years and the future - Jury KE (Proceedings of the New Zealand Society of Animal Production, 1990)
Eleven rising 2 year old red deer stags (127 kg LW) and five yearling steer (297 kgLW) were used to examine and compare pasture dry matter and water intake when grazing a rapidly decreasing pasture mass. The two groups grazed separately on adjoining 0.024 ha paddock breaks (12 per group) for 3 day periods. Mean pre and post-grazing pasture mass for both groups was 3400 (+/-80) and 1100 (+/-40) kg DM/ha. Pasture intake (g DM/kg LW0.75/d) for stags and steer respectively was 65, 93 (day 1) 44, 45 (day 2) 28, 25 (day 3). Results indicate that at pasture allowances greater than 4.0 kg DM/100 kg LW comparatively higher intake was achieved by steers. Daily pasture intake, expressed as a proportion of initial pasture intake (day 1), of stags was less affected by decreasing pasture mass (days 2 and 3) than steers. Voluntary water intake by stags was approximately one sixth that of steers (3.6 vs. 23.2 1/hd/d). When compared on the basis of 1/kg LW0.75/d, steers consumed 3.4 times more water than stags. Faecal dry matter content (%DM) differed between species, being 25.6% for stags and 14.7% for steers. These results indicate faecal water loss may be a major factor contributing to higher water consumption by steers.

The First 50 Years - Coop IE (Proceedings of the New Zealand Society of Animal Production, 1990)

Fleece weight and wool characteristics of Merino ewes screened into a superfine selection flock - Wuliji T; Land JTJ; Andrews RN; Dodds KG (Proceedings of the New Zealand Society of Animal Production, 1990)
One hundred and eighty cashmere wethers were divided into 11 treatment groups with 9 groups receiving a single melatonin implant at various dates staggered 6 weeks apart throughout the year commencing on 22 January 1988 and finishing on 22 December 1988. The tenth group received a melatonin implant at each of the treatment dates. The control group received no implant. Down lengths were collected at 1 to 6 weekly intervals to monitor growth patterns. The continuous melatonin treatment resulted in lower peak down lengths than controls in August while down lengths were higher than controls from October to January. However the period of down growth was unchanged. Shedding of down occurred 19 weeks after melatonin treatment in all groups except those treated on 15 April, 7 July and 18 August where the interval to shedding was shorter and in phase with the natural shedding cycle. Cashmere growth was only initiated following melatonin treatment from 18 August to 22 December. Treatment on 10 November increased cashmere production by 32 %. This was the only treatment which increased cashmere production harvested in one season.

The future impact of new opportunities in reproductive physiology and molecular biology on genetic improvement programmes - Baker RL; Shannon P; Garrick DJ; Blair HT; Wickham BW (Proceedings of the New Zealand Society of Animal Production, 1990)
During the serious outbreak of facial eczema (FE) in 1989, blood samples were obtained from first-lactation heifers born in 1986, in order to study any genetic influence on the incidence of FE. Heifers were located in 60 herds in Northland (14 herds), Auckland (25) and Taranaki (21). The herds were members of the New Zealand Dairy Board's 1985 Sire Proving Scheme for young Jersey bulls. Samples were collected from 1523 heifers, the daughters of 57 young Jersey sires and 19 other Jerseys including reference sires from previous years. Blood samples were analysed for gamma-glutamyltransferase (GGT), an indicator of liver damage such as due to FE. Overall, 28% of animals had elevated GGT values (>=30IU/1), and 72% (43) of herds had 2 or more animals with elevated GGT. After setting aside data from the 17 herds where no elevations of GGT concentration were recorded, the heritability of log e GGT was 0.31

Genetic analysis in sheep using hypervariable DNA probes - Hermans IF; Chambers GK; Jordan TW (Proceedings of the New Zealand Society of Animal Production, 1990)
No abstract supplied

Genetic parameters for in vivo body measurements in Suffolk sheep - Young MJ; Simm G (Proceedings of the New Zealand Society of Animal Production, 1990)
Attention is drawn to developments in the public perception of animal farming which have the potential to adversely affect the animal industry in the future. These developments, which are occurring around the world, stem from review of ethical aspects of animal farming and from concern at the ecological impact of animal farming. Of particular concern is the emission of greenhouse gases - especially methane - by ruminants. This paper discusses measures by which these emissions could be reduced, and how national policy decisions regarding greenhouse gas emissions on farms may be reached. Opportunities for this Society are pointed out.

The germline manipulation of livestock: progress during the past five years - Clark AJ; Archibald AL; McClenaghan M; Simons JP; Whitelaw CBA; Wilmut I (Proceedings of the New Zealand Society of Animal Production, 1990)
The role of endoparasitism on host nutrition was reviewed and the opportunities for manipulation considered with emphasis on two specific nutrients for which information is becoming available-protein and copper. The major effect of parasitism on protein metabolism is to increase the protein requirement of the host as a result of increased endogenous loss of protein rather than malabsorption per se. Protein supplementation has been shown to increase liveweight gain of infected sheep and to reduce faecal egg counts and worm burdens probably reflecting enhanced immunological competence of the host. Such rates of protein supply could be achieved in practice on temperature pastures if protein losses across the rumen could be reduced. Liver copper levels have been shown to be depressed by parasitism in the abomosum. The effectiveness of oral copper supplements depends on their ability to increase soluble copper levels in abomasal digesta, which is reduced by nematode-induced increase in pH. Intake depression has by far the greatest effect on production loss due to endoparasitism. Evidence is emerging that the mechanism for this depression has a peripheral hormonal and central neural basis. It was concluded that specific nutrient manipulation in plants or via supplements may enable the host to cope better with the debilitating effects of endoparasitism.

Goat fibre response to melatonin given in spring in two consecutive years - Welch RAS; Gurnsey MP; Betteridge K; Mitchell RJ (Proceedings of the New Zealand Society of Animal Production, 1990)
No abstract supplied

Growth responses of fat and muscle in the lamb to intra-arterial infusions of bovine insulin - Brief Communication - Wolff JE; Petrie DR (Proceedings of the New Zealand Society of Animal Production, 1990)
The purpose of this paper is to summarise recent findings on the reproductive physiology of the Booroola ewe, with specific attention to factors influencing ovulation-rate (OR). The ovarian antral follicle populations, incidence of atresia, steroid secretion-rate and maximum OR potential in the different Booroola genotypes (FF, homozygotes; F+, heterozygotes; ++, non-carriers) are the same notwithstanding the fact that FF, F+ and ++ animals normal ovulate >=5, 3-4 and 1-2 follicles respectively during each oestrous cycle. Moreover, the Booroola F gene does not appear to modify the characteristics of the follicle- stimulating hormone (FSH) or luteinizing hormone (LH) receptors, or the gonadotrophin-sensitive components of the cyclic AMP generating system or the steroid or inhibin biosynthetic functions in follicular cells. It seems that the F gene influences follicular growth before antrum formation resulting in fewer granulosa cells at all phases of antral growth and smaller sized follicles at ovulation. In essence, the >=5, 3-4 or 1-2 presumptive preovulatory follicles in FF, F+ or ++ ewes are respectively 2.5-4.5 mm, 4-5mm and >5 mm in diameter just before ovulation but the total populations of oestrogen-secreting follicular or progesterone-secreting luteal cells in the different genotypes are the same. These genotypic differences in ovarian characteristics have not bee replicated by any of the known superovulation regimes. At the level of the hypothalamus and pituitary no gene-associated differences have been noted in the concentrations of gonadotrophin- releasing hormone (GnRH) in the tissues or hypophyseal portal blood nor in the binding characteristics of GnRH to the pituitary gland. However F gene-specific differences have been noted in the plasma concentrations of FSH and LH in ovary-intact and ovariectomized (OVX) Booroola ewes (FF>++; P,0.05). The F gene-specific differences in FSH but not LH in OVX ewes can be replicated by exogenous GnRH treatment of OVX ewes deficient in endogenous GnRH following surgical disconnection of the hypothalamus from the pituitary gland but with the superior hypophyseal arteries being left intact. The greater frequency of high FSH values in ewes is also observed in both intact and castrate Booroola FF rams relative to ++ rams at P<=0.07. When considered altogether the evidence suggests that Booroola sheep with the F gene have higher mean FSH concentrations in plasma relative to ++ sheep. However the differences are small with considerable overlap between animals of the different genotypes. It therefore remains to be established whether modest increases in plasma FSH concentrations in ++ Booroola ewes are sufficient to modify follicular morphology and OR without altering steroid secretion.

Hogget fleece weight and fleece characteristics of Texel x Romney, Texel x Coopworth, Romney and Coopworth sheep - Wuliji T; Andrews RN; Davis GH; Farquhar PA (Proceedings of the New Zealand Society of Animal Production, 1990)
This study investigated apparent reproductive failure occurring in seasonally anoestrous progesterone-primed red deer hinds when they were induced to ovulate with the GnRH analogue, buserelin. In March 1988 (non-breeding season), each of 11 progesterone-primed red deer hinds(Groups B and BO) were injected i.m. with 4, 3, 2, 2 and 10 ug buserelin (Receptal, Hoechst) at -48, -24, 0, 24, and 48 h relative to the time injected i.m. with 500 ug oestradiol benzoate. During the breeding season (April), ovulation was synchronised in another 4 hinds (Group C) using CIDRs. Oestrous behaviour was less noticeable and delayed (P>0.05) in Group B hinds and peak LH levels were lower (P>0.01) and occurred later (P>0.01) relative to Group ), BO and C hinds. Two weeks after CIDR withdrawal 3/5 B, 2/4 O, 3/6 BO and 4/4 C hinds had a corpus luteum present. During theses two weeks plasma progesterone levels were elevated in B, BO and C hinds but were low in the O hinds. None of the buserelin- and/or oestradiol-induced ovulations resulted in pregnancy. These results show that ovulations induced in these anoestrous red deer hinds by the use of a GnRH analogue or oestradiol were not accompanied by normal hormonal and behavioural patterns.

How does the F gene influence ovulation rates in booroola ewes? A 1990 perspective - McNatty KP; Henderson KM; Fleming JS; Price CA; Clarke IJ (Proceedings of the New Zealand Society of Animal Production, 1990)
Currently most transgenic animals are produced by microinjecting DNA into a pronucleus of in vivo derived embryos. This is an inefficient procedure because of the costs of animals, superovulation and surgery, the low numbers of embryos produced, and their poor viability after injection. Thus, in most well run programmes, only about 10% of injected sheep, pig and cattle embryos result in offspring and only 0.5 to 1% in transgenic offspring. Methods for improving the efficiency are discussed and it is concluded that effective in vitro maturation (IVM), fertilisation (IVF) and culture techniques and alternative methods of gene insertion (particularly through stem cells or sperm - mediated insertion) would make significant contributions to improved results. Ruakura's successful sheep and cattle in vitro oocyte maturation, fertilisation and culture programme and its results are discussed. Recent developments in MOET techniques are discussed and it is concluded that, in the short term, it is possible that more effective multiplication of transgenics could arise from successful IVM/IVF and nuclear transplantation procedures than from significant improvements in current MOET technology. The in vitro produced egg therefore has considerable potential for increasing the efficiency of producing and multiplying transgenics.

Induction oestrus in the ovariectomised red deer with exogenous progesterone and oestradiol benzoate - Meikle LM; Fisher MW (Proceedings of the New Zealand Society of Animal Production, 1990)
Preventive control programmes for nematode infections of sheep, which depend upon strategically timed treatments of anthelmintics, are based on epidemiological knowledge of the time relationships between contamination of pastures and seasonal availability of infective larvae in different climatic regions. In Australia by the time these programmes were being actively promoted resistance to two of the three families of anthelmintic drugs had already emerged. A high prevalence of resistance is now widespread in Australia and measures for the management of resistance have been incorporated into recommendations of worm control. These include, a reduction in frequency of treatments, elimination of underdosing, assessment of effective drugs, their use at high dose rates in an annual rotation and the integration of treatment with grazing management. Nevertheless, there is concern that preventive control programmes may not be sustainable over the long term. Increased attention is now directed to alternative means of control, such as vaccination of sheep against nematode infections and breeding sheep with enhanced resistance to infection. The integration of these measures into preventive control programmes and the extent to which they can replace chemotherapy are topics for ongoing study.

The insulin status of sheep with genetic differences in glucose tolerance and carcass composition - Francis SM; Bickerstaffe R; O'Connell D (Proceedings of the New Zealand Society of Animal Production, 1990)
Twenty four Coopworth ewes, selected on the basis of an increased ovarian response to lupin grain supplementation, were ovariectomised and fitted with a Foley catheter in the abomasum. They were individually penned and offered a low protein pelleted diet at maintenance levels. Following a five week stabilisation period 12 ewes were infused abomasally with 100g/d whey protein concentrate in 1 litre of water for 8 days. Twelve ewes received 1 litre of water only. Blood samples were collected four times daily for FSH analysis, from 2 days before until 2 days after infusion. Protein infusion did not influence FSH levels. Mean values were 8.5 ngFSH/ml plasma for both treatments and means for individual ewes ranged from 4.5 to 11.5 ng/ml. These results indicate that the reported increase in FSH with increased protein intake is not due to a direct effect on the pituitary gland.

Intraruminal chromium controlled release capsules for measuring herbage intake in ruminants - a review - Parker WJ; Morris ST; Garrick DJ; Vincent GL; McCutcheon SN (Proceedings of the New Zealand Society of Animal Production, 1990)
No abstract supplied

Magnetic resonance imaging of live pigs to assess body composition - Davies AS; Baulain U; Henning M; Kallweit E (Proceedings of the New Zealand Society of Animal Production, 1990)
Two hundred 2-tooth (2T) and mixed age (MA) cashmere does were randomly allocated to one of 4 feeding levels to evaluate the effect of pasture allowance on liveweight change and reproductive performance. Pasture allowances of 0.8 (L), 1.2 (M), 2.5 (M+) and 5.0+ (H) kgGM/hd/d were imposed for 8 weeks prior to mating. Does were weighed fortnightly and laparoscroped at 10 (CL10) and 20 (CL20) days post buck introduction. Weight change over 8 weeks was -2.2kg (L), 0.1kg (M), 0.3kg (M+) and 1.8kg (H) and was significant (P<0.01) for L, M+ and H treatments. Pasture allowance had no effect on proportion of does ovulating (CL10 and CL20) but does on the L and M allowance averaged fewer multiple ovulations than does on the M+ and H allowances (14% vs 23%) at day 10 after mating. A high proportion (P,0.01) of MA does were ovulating 10 days after mating (78.7% vs 58.2%) and MA does had more multiple ovulations at 10 (52.1% vs 11.3%) and 20 (40.2% vs 13.5%) days after mating than 2T does. There were more (P<0.01) MA does pregnant (76.3% vs 57.1%) and more multiple pregnancies in MA does (44.6% vs 17.3%) than 2T does. This trial showed that age is a major factor in determining proportion of multiple ovulations and multiple pregnancies in cashmere goats. It highlighted the confounding effect of age on liveweight and the difficulty in separating the effects of pasture allowance from the effects of liveweight, on reproductive performance.

Mating performance of Texel rams - Davis GH; Knight TW; Sorenson E; Shackell GH; Holmes MR; Farquhar PA (Proceedings of the New Zealand Society of Animal Production, 1990)
Romney, Coopworth and Perendale ewes were accidentally exposed to facial eczema before May 1 hogget mating at 9 months of age. Serum gamma-glutamyl transferase (GGT) levels of individual animals were determined on 21 April. The ewes were divided into 3 classes for analysis based on the GGT levels: 1.<100 IU/1;2. 100-350 IU/1; and 3.>350 IU/1. At all matings over 4 years the ewes in class 3 had a lower fertility than class 1. These differences were only significant at the hogget and two-tooth mating. The total number of lambs weaned per ewe mated were class 1-5.0; class 2-4.4; and class 3-4.3 (P<0.1). There were no lifetime effects on fleece weight.

The measurement of serum immunoglobulin concentration to estimate lamb colostrum intake - Parker RJ; Nicol AM (Proceedings of the New Zealand Society of Animal Production, 1990)
Sixty-four wild possums, housed in individual cages, were divided into four groups based on sex and colour phase (dark or grey). The animals were assessed for fur quality and growth in March and were pair-matched for sex, colour phase, fur quality and growth. One possum from each pair was implanted with a 18 mg melatonin implant. By June there was a small improvement in fur quality which was independent of the localised regrowth of patches of missing fur. No overall change in the level of fur growth representing seasonal pelage renewal was recorded. The younger possums had a higher fur quality than older animals (p<0.001) but over the course of the experiment the difference (p0.05) than male pelts. Melatonin had no effect, either on pelt characteristics or on live weights.

Melatonin for cashmere production - Litherland AJ; Paterson DJ; Parry AL; Dick HB; Staples LD (Proceedings of the New Zealand Society of Animal Production, 1990)
Relative to an industry Romney control line, three lines derived from screening for high prolificacy, consisting of Romneys, Perendales and Coopworths had significantly heavier weaning weights after adjustment for non-genetic factors with weights of 19.9 (100), 22.3 (112), 24.0 (121) and 23.9 (120) kilograms (percentage relative to the Romney controls) for the respective flocks. The differences increase post-weaning and when slaughtered, between 175 and 219 days of age, the carcass weights (kg) were 12.0 (100), 14.3 (119), 16.1 (134), 15.7 (131) respectively for the different strains. Although the base populations of Romneys are not genetically comparable the results suggest that the intensive screening for prolificacy has indirectly resulted in animals capable of more rapid growth to slaughter. The differences between strains in their carcass weight adjusted subcutaneous fat depths were minor except that the high prolificacy Perendales had lower increases in fat depths with increasing carcass weight and had the lowest subcutaneous fat depths at heavy weights. Additionally the high prolificacy Perendales had 2 to 6 percent larger estimated L. dorsi areas than the other genotypes.

Milk production and plasma prolactin levels in spring- and autumn-lambing ewes - Peterson SW; MacKenzie DDS; McCutcheon SN (Proceedings of the New Zealand Society of Animal Production, 1990)
Methane and nitrous oxide produced by farmed ruminants may cause over one third of the potential greenhouse warming which can be attributed to New Zealand. This is a result of high populations of domestic ruminants (mainly sheep and cattle), and the large warming potential of methane and nitrous oxide. New Zealand's total greenhouse gas production is an insignificant component of the global total, but this fact cannot be used as a reason to ignore New Zealand's contribution. International negotiations have commenced with the aim of producing a treaty to limit global greenhouse gas production by ruminants in New Zealand, and identifies areas needing further research. It concludes that; (1) the accuracy of estimate of greenhouse gas emissions from agriculture needs to be improved; (2) technology to reduce greenhouse gas emissions from ruminants should be developed for, and applied to, New Zealand farming systems; and (3) that equitable methods of implementing limitation policies need to be investigated.

Milk production by cows grazing on Matua prairie grass (Bromus willdenowii Kunth) pastures maintained under difference - Rugambwa VK; Holmes CW; Chu ACP; Varela-Alvarez H (Proceedings of the New Zealand Society of Animal Production, 1990)
From a population of 1270 Coopworth ewe hoggets 70 were selected for high greasy fleece weight (CHFW) at hogget shearing and 50 controls were selected at random (CC). The CHFW ewes were joined in 1987 and 1988 to sires from a Romney high fleece weight (RHFW) flock, also mated contemporaneously within that flock. The CC were mated with commercial Coopworth rams. The CHFW and CC flocks were grazed with the RHFW flock and its control (RC). Results for progeny showed that relative to the RC (100) the greasy fleece weight of the RHFW, CC and RHFW x CHFW were 118, 112 and 125 respectively. Corresponding values for lamb fleece weight were 112, 106 and 121; and for October (12 month) live weight were 106, 109 and 114 respectively. RHFW rams crossed with CHFW ewes generated progeny markedly superior to Romney and Coopworth controls for greasy fleece weight, showing that appropriate breeding programmes can rapidly improve this trait.

A model for nematodiasis in New Zealand lambs: preliminary evaluation of strategies for nematode control - Leathwick DM; Barlow ND; Vlassoff A (Proceedings of the New Zealand Society of Animal Production, 1990)
During 1989, two groups of weaner red deer stags (n=18) grazed either perennial ryegrass (PRG) or Moata annual ryegrass (ARG) based pastures from mid-May until the end of November. Within each group, animals (n=6) were either not immunised or immunised against melatonin using Freund's or Dextran adjuvants. Treatment effects upon winter (W) and spring (S) LWG, proportion of animals attaining target liveweight (93kg; 50kg carcass weight by November 30), pasture composition, voluntary DM intake (VFI), anti-melatonin titres and plasma prolactin concentrations were determined. During winter, LWG (165 v 140 g/day; P<0.05) and VFI (1.62 v 1.20 kg DM/day; P<0.001) were greater for animals grazing ARG than PRG pastures, resulting in a greater proportion of deer attaining the target slaughter weight (60 v 41%). Organic matter digestibility and N content were higher (P<0.05) for the ARG than PRG pastures during winter. Maximum anti-melatonin titres of 1:15,215

Neuroendocrine control of growth hormone release in sheep: Effect of dose and route of administration of growth hormone releasing factor on plasma growth hormone levels - Spencer GS; Bass JJ; Hodgkinson SC (Proceedings of the New Zealand Society of Animal Production, 1990)
IN a factorial experiment involving 4 treatment affecting ovulation rate and 20 ewes per cell the effect of oestradiol was dominant, reducing the ovulation rate. In the non-oestradiol treated ewes a positive effect of high protein intake was evident. Phenobarbital increased ovulations in ewes on a low protein diet whilst carbon tetrachloride (CC14) had a slight negative effect only on the low protein diet. Neither phenobarbital or CC14 had any effect on the high protein diet. There was a decrease in plasma FSH at day 11 with oestradiol, protein and phenobarbital and an increase with CC14. Hence an increase in FSH does not always accompany increases in ovulation rate.

Nutrition effects on fibre quality in Angora goats during spring - Bigham ML; Bown MD; Clayton JB (Proceedings of the New Zealand Society of Animal Production, 1990)
No abstract supplied

Nutrition of the grazing ruminant - Black JL (Proceedings of the New Zealand Society of Animal Production, 1990)
Muscle fibres in the adult are giant multi-nucleated cells which originate in the foetus from myoblasts and later fuse to form myotubes. Protein deposition is the balance between synthesis and degradation. The proliferation of cells and protein metabolism is controlled by a variety of growth factors and hormones which in the whole animal influence lean deposition. This endocrinological control of growth can be exploited to enhance lean deposition in animals and some of the currently available and potential methods are reviewed. In most cases data would indicate that the animal must be fed a diet that will allow the increased potential for lean deposition to be expressed. Unfortunately many of the methods which have been shown to be safe for the consumer of the meat and the animal are not permitted for a variety of reasons by many government authorities. Future exploitation of the physiology of growth to enhance lean deposition is likely to be increasingly constrained by political decision; a luxury available to the affluent developed world.

Nutritional partitioning of growth for productive gain - Harris PM; Waghorn GC; Lee J (Proceedings of the New Zealand Society of Animal Production, 1990)
Artificial insemination (AI) is widely used throughout New Zealand dairy herds because it is convenient and allows herd owners to utilise semen from intensively selected genetically superior sires. The future focus of AI use will be to synchronise oestrus in maiden heifers and cows to further concentrate seasonal calving patterns. There will also be continued use of progesterone-based treatments to stimulate ovarian activity in anoestrous cows and to increase pregnancy rates in inseminated cows. Aspects of behaviour and marked seasonality in red deer and fallow deer currently present challenges to increasing the use of AI and controlled breeding in these species. It would be preferable to have fawning/calving in spring instead of summer, with or without the use of AI. However, the semen production of stags is best from 4 weeks after the onset of the induced or normal rut. This potentially increases the dependence on deep frozen semen and increases the need for the uterine deposition of sperm to increase sire coverage and achieve satisfactory pregnancy rates. Controlled use of hormones will produce altered calving/fawning dates and developing semen collection/processing techniques will increase the use of AI in deer.

Occurrence and effects of sub-clinical hypocalcaemia in dairy cows - Daniel RCW; Kerr DR; Mulei CM (Proceedings of the New Zealand Society of Animal Production, 1990)
The duration of melatonin release from Regulin implants and the diurnal variation in plasma melatonin concentration was investigated in 18 cashmere wethers, divided into 3 treatments: C-control; T-treated with melatonin 18mg Regulin implant on 10.11.88; PT - previously treated with melatonin every 6 weeks for 10 months before receiving an implant on 10.11.88. Mean concentration of plasma melatonin in T remained high 52 pg/ml for up to 42 days after implant, then declined to 8.5 pg/ml at 50 days remaining relatively low for the rest of the sampling period. Goats from PT maintained much high concentration of plasma melatonin 226 pg/ml for 42 days after implant. Control goats showed very low mean concentration at 5 pg/ml. Between animal variation in plasma melatonin concentration was high coefficients of variation were between 100% and 200% within all treatments. At 8 days post-implant plasma melatonin concentration of goats in C showed a nocturnal increase averaging 12.5 pg/ml, between sunset and sunrise. The same diurnal fluctations were evident at 29 days post- implant. Goats in treatment T also showed a nocturnal rise in plasma melatonin concentrations with average increases of 15 and 24 pg/ml at 8 and 29 days post implant between sunset and sunrise. It can be concluded that the melatonin implants used in this trial lasted for 42 days after administration and a nocturnal rise in melatonin concentration was evident in control and treated goats.

Oestrus activity in Booroola Merino, New Zealand fine wool Merino and Poll Dorset ewes from October to February - Knight TW; Kannegieter SG; Gibb M; Haack NA (Proceedings of the New Zealand Society of Animal Production, 1990)
No abstract supplied

The pastoral animal industries in the 21st century - Robinson JJ (Proceedings of the New Zealand Society of Animal Production, 1990)
Performance test data for ram lambs from a selection programme in a Suffolk flock were used to estimate heritabilities for and correlations (genetic and phenotypic) between three variables (liveweight, ultrasonic fat depth (FD and ultrasonic muscle depth in the live animal). Close agreement was found with previously published values with the exception of the heritability for FD for which a high value was estimated (0.55

Pasture dry matter and drinking water intake of grazing red deer stags and steers - Alexander GL; Segiura T (Proceedings of the New Zealand Society of Animal Production, 1990)
There has been considerable interest recently in the use of growth hormone (somatotrophin) to enhance growth, carcass leanness and milk yield in a number of species. Despite the similarity of bovine and ovine growth hormone, the administration of exogenous somatotrophin to lambs has produced disappointing results. Conceivably, stimulation of endogenous GH secretion may be more beneficial, and in this communication we present our preliminary results on the effective doses and rates of administration of growth hormone releasing factor in a study of the neuroendocrine regulation of growth hormone secretion in sheep. Sheep were housed indoors on a complete pelleted diet and were fitted with jugular vein catheters. Some sheep were also fitted with cannulae placed in a lateral ventricle of the brain. Bovine GRF was given at different doses to the sheep either intravenously (iv), intracerebroventricularly (icv) or intramuscularly (im) and plasma GH levels monitored. There was a dose-dependent increase in GH levels when the GRF was given iv, with both 30 and 3 ug being effective, while im administration was only effective at 30 ug. Central administration (icv) was also effective at both dose but did not stimulate GH release at 300 ng. Further studies are required to elucidate the mechanisms underlying GRF stimulation of GH release, but the efficacy of GRF as a growth promoter can be investigated using intramuscular administration.

Plants for grazing systems - Hodgson J (Proceedings of the New Zealand Society of Animal Production, 1990)
The somatotrophic axis has a major effect on lean growth in a number of species. GH, the main hormone of the somatotrophic axis, is controlled by growth hormone releasing hormone and somatostatin. GH can act directly on fat by increasing lipolysis, but its main anabolic effects are on muscle and bone via the Insulin like growth factor-I (IGF-I). IGF-I stimulates amino acid uptake into muscle in vitro but does not necessarily promote growth if given in vivo. The reason for this is that GH is now considered to control circulating IGF- I as well as local tissue production of IGF-I, the dual effector theory. This theory proposes that GH not only controls IGF-I production but controls differentiation of cells so that they can respond to the mitogenic effects of IGF-I. Insulin is another anabolic hormone which is affected by GH. Insulin, unlike GH, stimulates fat deposition, although it also increases protein accretion. The manipulation of the growth hormone axis by immunological procedures, selection or genetic engineering may provide an economic way for NZ farmers to increase the production of lean meat.

Plasma urea dilution patterns in Southdown ram lambs from high and low backfat selection lines - Abdullah AY; Purchas RW; McCutcheon SN; Van Dinther PC (Proceedings of the New Zealand Society of Animal Production, 1990)
Exogenous progesterone and oestradiol benzoate (OB) were used in long-term ovariectomised red deer to investigate a simple technique for induction of oestrus. Up to 12 days of intravaginal progesterone (CIDR-S; replaced at 4 day intervals) was followed 24h later by a single intramuscular injection of OB. Continual observations (for behavioural oestrus) and blood sampling every 6h (for plasma LH concentrations) were conducted over the subsequent 48h period. In Experiment 1 (December), 12 days of progesterone preceded 0, 1.0, 2.5 or 5.0 mg OB. Onset of oestrus (28-44h post-OB; mean 33h) was similar in all treated hinds. Plasma LH concentrations fell (P<0.01) after OB administration, followed 30 to 36h later by a dramatic increase (to 6.4 ng/ml) indicative of pre-ovulatory-like LH surge. Hinds receiving no OB exhibited 4% of all mounting interactions but showed no increases in LH concentration. Experiment 2 (January) consisted of no treatments or 12 days or progesterone followed by 0, 0.1 or 1 mg OB resulted in suppression of plasma LH after OB. However, all other plasma LH and behaviour responses elicited were anomalous. In Experiment 3 (February), 0,4, 8, or 12 days of progesterone pretreatment were terminated 24 hours prior to administration of 1 mg OB. Plasma progesterone concentrations were elevated above 1 ng/ml during all progesterone treatments. Onset of oestrus was observed later (P<0.5) after 4 days of progesterone treatment (33.4h; sem 1.2h). Tonic plasma LH secretion was elevated (P<0.01) from Experiment 1 through to Experiment 3 but the plasma LH suppression in response to OB was similar in all 3 experiments. These results indicate that oestrus can be induced in the red deer hind by at least four days of intravaginal progesterone treatment followed by i.m. oestradiol benzoate administration 24h after progesterone removal.

Postweaning growth and carcass leanness of lambs that differed in preweaning growth rate - Bray AR; Moss RA; Burton RN; Saville DJ (Proceedings of the New Zealand Society of Animal Production, 1990)
An experiment was conducted to investigate the effect of nutritional status on fibre quality from Angora goats during spring. Two groups of 28 non-pregnant Angora does were grazed on ryegrass/white clover pasture at one of two pasture allowances; 1.0 kg and >4kg DM /head/day (low and high respectively) for twelve weeks during spring. Groups were balanced for live weight, age, fibre diameter, medullation and kemp measurements and genetic background. Live weight and fibre quality (fibre diameter, % medullaltion and % kemp) were measured at the start, after 6 weeks and at the end of the experiment. Mean live weight of does at the start of the experiment was 22.6 + 0.20 kg and after 12 weeks 30.9 and 25.2; sed 0.63kg for high and low allowance respectively. Neither mean fibre diameter (35.2 vs 34.1; sed 0.66 microns) nor medullation (5.38 vs 6.51;s ed 53%), was affected by pasture allowance over the experiment (high and low allowance respectively). However, after 12 weeks, there was a trend for % kemp measured in the fleece in does on high pasture allowance to be higher than in does on low allowance (8.16 vs 6.52; sed 1.04%). All does were fibre tested again in March 1989 after grazing at a common allowance, but differences in fibre characteristics between the previous spring pasture allowances treatments were small. It appears that doe nutrition during spring can influence the kemp content in the Angora fleece. The mechanism of this effect is, however, not known.

Present and future grazing systems - Bryant AM (Proceedings of the New Zealand Society of Animal Production, 1990)
Various tissues in the sheep, because of their individual specialist roles, have very different nutrient requirements. These differences in metabolic behaviour provide a potential opportunity to manipulate biochemical pathways in specific peripheral tissues to enhance production characteristics and, consequently, commercial gain. Factors affecting such partitioning are discussed with particular reference to the sheep industry in New Zealand, which unlike most other international sheep systems, needs to produce meat and wool from the same animal. Because the relative returns from meat and wool vary from season to season there is a need to manipulate independently their relative production to achieve maximum economic return.

Regulation of growth by the growth hormone axis - Bass JJ; Gluckman PD (Proceedings of the New Zealand Society of Animal Production, 1990)
The bovine conceptus induces an array of physiological and biochemical responses that lead to the establishment of pregnancy. Among the most studied of these is secretion of prostaglandin (PG) F2alpha (F) from the uterine endometrium. Pregnancy appears to be associated with laterations in many of the regulatory systems that cause PGF secretion leading to luteolysis in cyclic animals. The conceptus secretes an antiluteolytic protein (bovine trophoblast protein-1 complex [bTP-1] that appears to induce an inhibitor of prostaglandin synthesis. The bTP-1 antiluteolytic protein is an alphaII interferon. The secondary effects associated with interferon-like activities (antiviral, antiproliferative, altered gene expression, immunosuppressive) may complement development and sustenance of the conceptus. Both ovarian CL function and follicular activity are altered in early pregnancy. Changes in follicular activity may reinforce the antiluteolytic signals from the conceptus leading to maintenance of the CL. Potential management systems to improve reproductive efficiency that are based on supplementation with bTP-1-like molecules, controlled ovarian follicular management, and progesterone therapy are discussed.

Responses in venison production to grazing pastures based upon perennial ryegrass or annual ryegrass and to immunisation against melatonin - Ataja AM; Wilson PR; Hodgson J; Hoskinson RW; Purchas RW; Varela-Alvarez H; Barry TN (Proceedings of the New Zealand Society of Animal Production, 1990)
Annual patterns of fur growth are described from captive possums skin biopsied at three-weekly intervals between April 1985 and May 1987. Counts of hair follicles showed that follicle activity was poorly synchronised between individual possums, with maxima occurring mostly in spring and summer. No more than 40% of follicles sampled were active at one time in any individual. Derived follicles continued to develop in adult animals, increasing the follicle population by 23

Responses to modern technology within the New Zealand sheep breeding industry - Harvey TG; Haydon R; Blair HT; Daniell D; Hilson R (Proceedings of the New Zealand Society of Animal Production, 1990)
In 34 lactating ewes (10 fistulated at the rumen and abomasum), herbage intakes were calculated using herbage digestibilities estimated either in vitro, or by using the plant cuticular wax component pentatriacontane (C35 alkane) as an internal marker. Alkane-based herbage intakes in intact ewes rose from 1672g OM/d at 14d of lactation to 2798g OM/d at 42d. In the fistulated ewes, the equivalent herbage intakes were 1736 and 2240g OM/d respectively. Alkane-based and in vitro-based intakes were not significantly different at 14d of lactation in either intact or fistulated ewes. Later in lactation, alkane-based intakes were significantly higher in both groups of ewes. In the fistulated ewes, estimates of the proportion of digested OM apparently disappearing across the rumen and of the efficiency of microbial protein synthesis were calculated from abomasal flows of digesta and microbial protein. These results suggested that the alkane- based herbage intakes were the more accurate.

Seasonal fibre replacement and harvesting of fur in brushtail possums (Trichosurus vulpecula) - Nixon AJ (Proceedings of the New Zealand Society of Animal Production, 1990)
No abstract supplied

The sheep's immune response to nematode parasites and prospects for its exploitation - Douch PGC (Proceedings of the New Zealand Society of Animal Production, 1990)
Perennial ryegrass (RG) and Matua prairie grass swards of low (LMPG) and high (HMPG) pre-grazing herbage masses were compared in 8 grazing trials (2-3 weeks) during early spring, late spring, summer and autumn (1987/88 and 1988/89) to assess their feeding values. Pre- grazing masses were approximately 3000, 4000 and 5500kg DM/ha for RG, LMPG and HMPG treatments, respectively. Friesian cows (8 per treatment) were allowed 50 kg DM/cow/d. Mean concentrations of N (% in OM) and OMD (%) for RG, LMPG and HMPG herbage were 2.7, 2.6, 2.3 (s.e.lsm 0.04, P<0.001); and 74.7, 73.1 and 70.7 (s.e. 0.18, P<0.001), respectively, HMPG values were lowest during all seasons and were influenced by high compositions of dead material, low leaf:stem ratios and low compositions of clover in the swards. Daily yields of milk and protein on RG swards were 3% higher (P<0.05) than LMPG yields, and 11 and 13% higher (P<0.001), respectively than those of HMPG swards. Milkfat yields were similar on RG and LMPG swards, but were 11% lower (P<0.001) on the HMPG treatment. The results indicate that leafy prairie grass and leafy ryegrass swards have similar feeding and productive values. Further research is needed on Matua's persistence under grazing.

Studies into the mechanisms by which nutrition influences ovulation rate: use of the ovariectomized ewe model - Cruickshank GJ; Smith JF; Konlechner J; Parr J (Proceedings of the New Zealand Society of Animal Production, 1990)
Gene transfer offers vast potential for improvements in animal agriculture. Improvements in quantity, quality and efficiency of production as well as entirely new forms of production can be envisage. Realising this potential, however, is hampered by dilution and duplication of effort, an acute shortage of trained personnel, and the perceived gulf between scientific developments and the launching of a product on the market. Overcoming these obstacles will require participation in decision-making by experts from other fields as well as science, and national co- ordination of effort coupled with identifiable, committed funding from government and the private sector. Producer groups and professional societies such as the New Zealand Society of Animal Production should play a leading role in these developments.

Studies on the physiological basis of appetite depression in nematode infection in sheep - Dynes RA; Ankersmit AEL; Poppi DP; Barrell GK; Sykes AR (Proceedings of the New Zealand Society of Animal Production, 1990)
The influence of preweaning growth rate on postweaning growth and carcass grading characteristics was investigated in two experiments with lambs at pasture. Differences in preweaning growth rate due to within mob variation, feed allowance treatments or rearing rank had small or no effects on postweaning growth when lambs were offered the same pasture allowance per unit of liveweight or per head after weaning. Therefore lambs with slower preweaning growth rates had lighter carcasses at a common age (P<0.01) or were older at a common weight (P<0.05). Carcass GR measurements were not significantly influenced by preweaning growth rates when compared at the same carcass weight and slaughter date. An increase in weight-adjusted GR measurements was observed over autumn.

Understanding and exploiting the physiology and endocrinology of reproduction to enhance reproductive efficiency in cattle - Thatcher WW; Hansen PJ; Plante C; Badinga L; Van Cleeff J; Danet-Desnoyers G; Savio JD; Mirando MA; Bazer FW (Proceedings of the New Zealand Society of Animal Production, 1990)
The FSH:LH bioactivity ratios, determined by radioreceptor assays, of four commercial gonadotrophin preparations were Folligon 5; F.S.H.-P. 18; Folltropin 49 and Ovagen 1090. The mean number of oocytes produced in immature rats after ovulation induction following administration of these gonadotrophin preparations by injection (Folligon, 10 to 50 i.u.) or 48h continuous infusion (others, 30 to 1000 ug/day) was dose-dependent, except at the highest doses when mean oocyte numbers either remained unchanged, or fell significantly in the cases of Folligon and F.S.H.-P. The highest mean number of oocytes produced in response to Folltropin (48+9) and Ovagen (47+7) were significantly higher (P<0.05) than those attained with Folligon (21+6) or F.S.H.-P (31+5). Mean ovarian weights also increased in a dose-dependent fashion in response to each of the gonadotrophin preparations. Co-infusion of NIADDK-ovine LH-25 at 10 to 20 ug/day with Ovagen (250 ug/day) or NIADDK-ovine FSH-17 (10 ug/day) (both low in LH activity) increased mean oocyte production 1.5 to 3-fold. Co-infusion of ovine LH at 40 ug/day significantly reduced mean oocyte numbers.

Use of high fleece weight Romney rams for out-of-season lambing - Reid TC; Monigatti AC (Proceedings of the New Zealand Society of Animal Production, 1990)
The export of live sheep by sea to the Middle East is an area of public concern due, in part, to the high death rates on some voyages, and to the perceptions of poor animal welfare during transport. This paper review the history of sea transport of sheep, the practice, investigations, welfare guidelines, and management progress in the New Zealand live sheep trade. A recent study of sheep exported to the Middle East has identified important behavioural indicators of stress and welfare. The results of this study have led to the implementation of new management systems to meet the identified behavioural characteristics and requirements of British breed sheep. Voyage mortalities consistently less than 1% in sheep transported from NZ to the Middle East can be expected.

The use of the somatic cell count of composite milk samples to predict the infection status of the udder in cows from New Zealand dairy herds - Holdaway RJ; Holmes CW; Steffert IJ (Proceedings of the New Zealand Society of Animal Production, 1990)
No abstract supplied

What the market will need from milk production - Fenwick RM; Kirkpatrick KJ (Proceedings of the New Zealand Society of Animal Production, 1990)
DNA profiles, or fingerprints as they are often called, provide the basis for a powerful parentage test that has a number of applications for the animal breeding industry. Two examples of its use are presented here. During a breeding program where single sires were being mated to groups of ewes, two groups became mixed, compromising the experiment. Using DNA profiling results, each of the progeny could be assigned to one of the two rams. The second example involves the auditing of pedigrees which the Booroola gene is segregating. In searching for a DNA marker that segregates with the Booroola gene it is essential that flock records are accurate. In one pedigree a number of individuals that were wrongly assigned as daughters of a heterozygous Booroola sire were identified. In another pedigree all daughters were correctly assigned.

Wool production and other characteristics of progeny from high performance Coopworths x Romney rams - Andrews RN; Dodds KG; McEwan JC; Wuliji T (Proceedings of the New Zealand Society of Animal Production, 1990)
Masked by the short-term influences of under or over-production at national level, concerns about the quality and hygiene of animal products and fears regarding dietary influences on human health, long- term projections of what will be expected of the pastoral animal industries are difficult to make. Concerns about the welfare of animals in intensive systems coupled with the political changes taking place in Russia and Eastern Europe are likely to swing animal production more towards pastoral systems. The removal of large quantities of fat from the food chain is likely to become a permanent feature. So too is the trend for a more even flow of high-quality products on to the market. In meeting these goals the role of the current biotechnological revolution, both directly in primary animal production, and indirectly through its contribution to the animal-product and food-processing industries, will be essential. We can not afford intellectual scientific complacency in a world where famine could, however remotely, become a truly global phenomenon. It is against this background that those aspects of the pastoral animal industries that currently limit production are viewed and the opportunities for implementing new technologies outlined.

An alternative hogget-two tooth shearing policy for summer-dry regions in New Zealand - Parker WJ (Proceedings of the New Zealand Society of Animal Production, 1989)
No abstract supplied

Artificial insemination of farmed feral goats with frozen-thawed semen - Moore RW; Dow BW; Staples LD (Proceedings of the New Zealand Society of Animal Production, 1989)
A trial was conducted over 2 years in which the comparative wool growth rates of wethers and dry, single and twin-rearing ewes were measured. The sheep were pasture fed according to 3 regimes of either continuous maintenance or alternating 3-monthly periods of either high or low plane and maintenance feeding. At any one time, groups of sheep were either gaining, maintaining or losing live weight. This paper reports preliminary analyses of the effects on wool growth of year, breed, sheep age and rearing status. Coopworths were consistently heavier than Romneys. As a result of practical constraints associated with the trial design, ewes which reared twins were lighter at the end of the trial than ewes which reared singles which were lighter than wethers and ewes which did not raise any lambs. Romneys grew more wool than Coopworths with no difference in wool production between wethers and ewes which did not rear a lamb. Overall, the clean wool growth rate of the dry sheep was a minimum of 7.2 g/d in July/August and a maximum of 12.5 g/d in November/December. Wool growth rates of the single and twin rearing ewes relative to the dry sheep (100) were 63 and 55 in July/August and 90 and 82 in November/December respectively. Wool growth rates after weaning did not differ between rearing status groups. The combined effect of these differential wool growth patterns on clean fleece weight of single and twin rearing ewes relative to the dry sheep (100) were 86 and 77 in December and 99 and 97 in May respectively. Despite the apparent large reduction in wool production associated with rearing lambs it is still economic at present prices for most farmers to run breeding ewes rather than dry sheep of the same breed.

Biological efficiency for venison production in red deer - Fennessy PF; Thompson JM (Proceedings of the New Zealand Society of Animal Production, 1989)
To study the influence of melatonin on seasonal changes in wool production of crossbred sheep, a pharmacological dose of sustained release melatonin was administered over a month in early summer to both fleeceweight-selected and control rams from the Massey university Progeny Test lines. Wool growth and testis diameter were compared with those of untreated animals during the period of melatonin treatment and for a further 2 month period. Melatonin treatment did not significantly change either greasy or clean fleeceweight production. However, the testis diameter of the melatonin- treated animals was significantly greater than in untreated animals during the period of melatonin treatment and significantly smaller during the recovery period. Hence, although the melatonin treatment was sufficient to produce a change in reproductive characteristics, it was not sufficient to induce a measurable change in the pattern of wool production.

Breeding season of Romney and Poll Dorset ewes at different locations and the reproductive penalties of a June joining - Knight TW; Kannegieter SG; Hamilton GJ (Proceedings of the New Zealand Society of Animal Production, 1989)
The age at which permanent incisor teeth came into wear was recorded in 23 yearling flocks that differed in breed and management, and one mixed-age flock, of spring-born sheep. In female yearling flocks the first pair of incisors came into wear at a median age of 15 months, with a normal range of 13 to 17 months. Variation within flocks was seven times greater than between flocks. Teeth erupted 21 days earlier in male lambs than in half sib sisters. Time of eruption was not affected by lamb breed, date of birth or growth path. Data from the yearling flocks identified a substantial pool of animals older than 12 months of age that did not have two incisors in wear. These animals could be given dispensation for grading as lamb after the normal cut-off date if incisor teeth in wear is accepted as the cut-off criterion. This would help overcome the shortfall in supply of lean, heavy carcasses that occurs each spring before new season's lambs reach suitable size. In the mixed age female flock, the median ages when 2, 4, 6 and 8 incisors came into wear were 15, 23, 30 and 42 months. Later pairs of incisors came into wear earlier than commonly assumed and individuals with the same number of incisors varied in age by up to two years. These findings highlight substantial limitations to the use of number of incisors for determining age in sheep.

Carcass composition of New Zealand Saanen goats - Colomer-Rocher F; Kirton AH (Proceedings of the New Zealand Society of Animal Production, 1989)
Resistance and the 'self-cure' phenomenon were examined in Coopworth lambs and Saanen kids when they were between 6 and 8 months old. The animals had been reared on pasture from birth until February 1987 at which time they were treated with anthelmintic and withheld from pasture for two weeks. They were given Trichostrongylus colubriformis (500 infective (L3) larvae kg-1) weeks after the initial dose. Faecal egg counts estimated at weekly intervals were significantly higher in kids than in lambs throughout the experiment. Furthermore, a strong acquired resistance was effected in the lambs subsequent to and as a result of the second dosing. The kids failed to show a similar response. Worm counts estimated at necropsy confirmed that spontaneous rejection, against Trichostrongylus and Ostertagia had been produced only in the lambs. These results how clearly that there are some significant differences between grazing lambs and kids in their ability to acquire and sustain a resistance to nematode parasites.

Changing the body composition of sheep by feeding - Cropper MR (Proceedings of the New Zealand Society of Animal Production, 1989)
Effects of autumn-winter feeding level on live weight and the timing and success of hogget mating were studied in 180 cashmere doe hoggets bred from ferals in each of 2 years. They were fed pasture allowances of 0.8 (L nutrition) or 3 kg DM/hd/d (H nutrition) from 10 March to 30 June in 1986 and from 1 May to 10 July in 1987. Start live weights were 13 and 13.3 kg in 1986 and 1987, respectively. In both year H and L hoggets entered a period of weight stasis. H and L group live weight increased to 15.2 and 13.9 kg respectively by 2 May 1986 and then remained almost static. In 1987 H live weight increased to 14.8 kg by 29 May before stasis. L live weights declined slightly. Entire bucks were joined from 1 May to 12 June each year. Teasers were present outside of these times. Peak incidence of puberty occurred between 14 and 29 May in both years and for both H and L treatments. More H hoggets showed oestrus than L hoggets (74 v 37% in 1986 and 62 v 42% in 1987). This reflected in a greater percent of H hoggets diagnosed as pregnant when scanned ultrasonically in July (HP/HJ) of 45% v 18% in 1986 and 50% v 34% in 1987. High nutrition appeared to improve hogget puberty rate over and above its effect on live weight in 1986 but not in 1987. Low levels of cashmere down production were recorded (57 g) and these were not influenced by differences in nutrition.

CIDR-B for managed reproduction in beef cows and heifers - McMillan WH; Macmillan KL (Proceedings of the New Zealand Society of Animal Production, 1989)
There is a long-standing disagreement about the influence that feeding has on body composition, particularly in ruminants, yet the problem remains of finding ways to produce lean lambs. This paper attempts to revive the view that feeding can alter, independently, the rate of growth and the relative rate of fattening in sheep. A numerical illustration is given of the relationship between a lamb's potential for growth, its feed requirements and the rules it uses to partition feed resources when they are scarce. For simplicity, the feed is considered only in terms of its metabolisable energy; digestible crude protein ratio. Published data are then review to test whether it is reasonable to retain the proposed theory. The review closes with a discussion of our current options and future possibilities for changing body composition by feeding.

Comparative effects of dietary molybdenum concentration on distribution of copper in plasma in sheep and red deer (Cervus elaphus) - Osman NHI; Sykes AR (Proceedings of the New Zealand Society of Animal Production, 1989)
Implants of melatonin can improve reproductive performance in sheep but timing of joining is important. In this study, 531 Coopworth ewes were used in a 2x4 factorial design to investigate the effects on reproductive performance of Regulin (melatonin) implants and time of joining. Implanted ewes were treated about 1 month prior to joining on either 1 December, 15 December, 29 December or 12 January. Control ewes were untreated. Matings with Poll Dorset rams were recorded fortnightly until the rams were removed on 5 February. About 10% of the implanted and control ewes joined on 1 December mated by 29 December. By the end of joining, over 90% of these early joined ewes had mated. Melatonin treatment had no effect on mating pattern in these 2 joining groups. By contrast, melatonin treatment improved the total number of ewes mated when joined on 29 December (100% v 58% P<0.001). About 50% of the treated and control ewes joined on 12 January had mated by the end of joining, but not melatonin treatment affected return to service rates. Melatonin treatment reduced the pregnancy rate in ewes joining on 1 December and 15 December (69% v 83% P<0.01). In contrast, melatonin treatment increased the pregnancy rate for 29 December joinings (72% v 41% P<0.001) but not 12 January joinings (49% v 46%). The incidence of multiple pregnancies was increased by melatonin treatment (40% v 30% P<0.05). The melatonin treatment trend was for fewer lambs per ewe joined for early joining times to more lambs per ewe joined for later joining times. These results demonstrate that reproduction responses to melatonin implants are very sensitive to time of joining. With a late December to mid January joining time and an early February end of joining, between 20 and 40 more lambs per ewe joined was achieved in this study. The onset to the breeding season in these Coopworth ewes is about 2 months earlier than expected. The use of Poll Dorset rams may be an important factor in this early onset.

Construction of a bovine gene map - Hetzel DJS (Proceedings of the New Zealand Society of Animal Production, 1989)
A single intramuscular injection of 10g of Buserelin (Bus), a potent analogue of gonadotrophin releasing hormone (GnRH) was administered to non-lactating Holstein cows (Experiment 1) or Brangus cross animals (Experiment 2) on cycle day 12 (oestrus + cycle day 0). This treatment altered normal patterns of ovarian follicle development, causing atresia or premature luteinisation especially in follicles of 6 to 9 mm diameter. Injecting 8 or 10g Bus every third day from cycle day 12 to cycle day 48 (Experiment 3), extended the average inter-oestrous interval to 56.2 days, maintained diaoestrous concentrations of plasma progesterone (5 to 12 ng/ml), and increased corpus luteum lifespan to at least 49 days in 5 of 6 Holstein cows. This 3 day interval was also used with 18 cows and heifers which were embryo recipients when they had been in oestrus from 2.5 to 7.5 days before their contemporary embryo donors (Experiment 4). The average pregnancy rate following these asynchronous transfers was 38.9%, varying from 20% when morulas were transferred to 62.5% with blastocysts. Inserting a CIDR-B into heifers 12h after the onset of oestrus for 3 to 15 days produced alterations in inter-oestrus intervals which indicated that progesterone treatment during metoestrus could potentiate the capacity of the uterus to synthesise and release prostaglandin F2a (Experiment5). The results from these five experiments showed that manipulating ovarian follicle development with Bus, or altering normal follicle-uterine interactions could be utilised as forms of oestrous cycle control which may be applied after insemination or embryo transfer.

Control of the oestrous cycle in farm animals: A review - Swanson LV (Proceedings of the New Zealand Society of Animal Production, 1989)
The pregnancy status of over 4700 ewes, divided into 21 flocks (137 to 688 ewes) and grazed on 14 properties in the Hawkes Bay, were diagnosed using either or both real time ultrasonic body scanner (ultrasonic) and video-fluoroscopy (X-ray) systems. The diagnosis was checked with the number of lambs born, dead or alive, to each ewe. For the ultrasonic system the percent of ewes whose lambing status was correctly predicted ranged from 96.1 to 100% for 19 flocks examined. In the case of the X-ray system the values for 13 flocks examined, except for one property, ranged from 94.3 to 99.6%. The operators must have a special aptitude in handling the instruments and interpreting an image on a screen if good results are to be obtained. The maximal throughputs for the ultrasonic and X-ray systems were 200 and 250 ewes per hour respectively. The major differences between the two systems (ultrasonic v X-rays) were: i) The capital outlay for the ultrasonic system was about a twelfth of that of the mobile X-ray system. ii) A good backup service is needed to maintain the X-ray equipment. iii) To sustain a throughput of over 200 ewes per hour, excluding the operator, 5 labour units were required for the sheep handling associated with the ultrasonic system compared to one for the X-ray system.

Correlated responses in a weight-selection experiment with beef cattle - Morris CA; Baker RL; Hunter JC (Proceedings of the New Zealand Society of Animal Production, 1989)
Two experiments investigated the post-weaning nutritional requirements and subsequent growth rates of lambs born in May and June. The objective was to produce heavyweight lamb carcasses during the period of otherwise difficult supply (November to January). Experiment 1 examined the feed intake, growth rate and carcass composition of ram and ewe lambs born in late May (weaned late July) offered three pasture allowances. Pasture dry matter allowances of 6%, 12% and 22% of liveweight/head/day resulted in average growth rates of 68, 1109 and 148 g/d, respectively in weaned lambs over the period from July to January. Experiment 2 investigated growth rates of June born lambs fed pelleted supplements (420 g DM/head/day) at pasture. Weaned ram lambs were offered either high protein, medium protein or no supplements at two pasture allowances (12% and 22% of live weight/head/day) for 12 weeks between September and December. At the low pasture allowance the high protein supplement gave a 13% improvement in growth rate (P<0.05) over the medium protein supplement. For the final six weeks of the experiment, half of the high pasture allowance group was offered a white clover dominant pasture. Over this latter period the "clover" group had significantly higher growth rates (233 g/d) than lambs offered either high protein (204 g/d) or medium protein (184 g/d) or no supplements (161 g/d) at high pasture allowances. Carcass weights at slaughter (11th December) were 19.6, 18.6, 18.2 and 16.5 kg, respectively, for these four groups. High protein supplements at pasture increased lamb growth rates, particularly at a low pasture allowance. This would be useful during times of poor or unseasonal pasture production to ensure supply contracts are met, particularly for early, heavyweight lambs.

Development of cattle of superior genotypes: Novel approaches to increasing tolerance of dairy cows to extended milking intervals - L'Huillier PJ; Davis SR; Carruthers VR; Morris CA; Bryant AM (Proceedings of the New Zealand Society of Animal Production, 1989)
Active immunisation of Romney ewes with bovine follicular fluid (bFF) at monthly intervals for 4 months in the breeding season increased monthly mean ovulation rates by 8 to 100%, relative to non-immunised ewes, by increasing the frequency of double ovulations. The increases in ovulation rate were independent of the dose of bFF (from 1 to 10 ml) and whether an aqueous- or oil-based adjuvant was used. Immunisation with porcine FF (1 or 5 ml) did not increase ovulation rates significantly. Active immunisation with an androstenedioned-based immunogen (Androvax), increased the mean monthly ovulation rates 31 to 63% by increasing the frequency of double and triple ovulations. Immunisation with bFF and Androvax together did not increase ovulation rates any more than immunisation with Androvax alone. These results show that active immunisation with bFF can increase ovulation rates in sheep, though generally less effectively than by immunisation with an androstenedione-based immunogen.

Development of cattle with a modified genotype: Embryological techniques needed for the efficient production of transgenics - Thompson JGE; Peterson AJ; Tervit HR (Proceedings of the New Zealand Society of Animal Production, 1989)
The manipulation of ovulation rate in the red deer hind was investigated by administration of steroid-free bovine follicular fluid (bFF). Twenty-four adult hinds, treated with intravaginal progesterone (CIDR), received a daily intramuscular injection of either 0, 4, 7.5 or 11 mls of dextra-charcoal treated bFF (n = 6 per group) on days -1, 0 and +1 from the time of CIDR withdrawal. After CIDR removal, plasma progesterone concentrations declined in all animals. In control hinds, oestrus occurred 2-3 days later and mean plasma progesterone concentrations began to increase thereafter. In bFF-treated hinds, oestrus was delayed by 3-5 days, and plasma progesterone concentrations remained low for at least 7 days after CIDR withdrawal. Plasma LH concentrations were 2-3 fold higher in the bFF- treated groups, relative to the control hinds, for at least 6 days after the end of bFF treatment. Twin ovulations were recorded in 1/6 control and 5/17 treated animals. At pregnancy diagnosis, 10/23 hinds were pregnant having conceived at the treated oestrus (3/6 control and 7/18 treated), but none had more than one foetus. There was no evidence of a dose-response to bFF treatment. These results indicate that in the hind, bFF can be used to manipulate the timing of oestrus and ovulation rate. A component(s) of bFF may thus have the potential to regulate fecundity in deer.

Do melatonin implants influence the breeding season in Coopworth ewes? - McMillan WH; Sealey RC (Proceedings of the New Zealand Society of Animal Production, 1989)
Although the Booroola F gene increases litter size in the ewes by one lamb there have been no unequivocal reports of its expression in the ram. In this report the presence of the F gene in the ram has been shown to increase sperm swimming speed and a sperm activity index as measured by a dual and single beam laser respectively. The lambing rate of ewes artificially inseminated with sperm from rams with the FF genotype was slightly higher than those inseminated with sperm from rams without the F gene.

Early lambing in Hawkes Bay: The effect of pasture allowance and protein supplementation at pasture on lamb growth rates - Muir PD; Wallace GJ; Smith NB; Ryan AM (Proceedings of the New Zealand Society of Animal Production, 1989)
Groups of Coopworth ewes were mated to Polled Dorset rams at 2 monthly intervals for 12 months following induced ovulation and synchronised oestrus. The ram lambs were made cryptorchid and grown to a target slaughter liveweight of 40 kg. The influence of birthdate on birthweight, pre- and post-weaning growth rate, time from birth to slaughter and carcass leanness was studied. The major influence on lamb performance was the timing of lambing in relation to spring pasture growth and the subsequent summer period, characterised by low pasture growth and quality. When late gestation was during summer lamb birth weight was lower (3.5 and 3.6 kg for January and March born lambs respectively) than for other periods (4.3, 4.4, 4.8 and 4.5 kg for May, July, September and November born lambs respectively). Similarly, pre- and post-weaning growth rates were higher during spring (pre-weaning maximum, 276 g/d for lambs born in July; post-weaning maximum 223 g/d for lambs born in May) and lowest during summer (pre-weaning minimum 150 g/d for lambs born in November, post-weaning minimum 123 g/d for lambs born in September). Age at slaughter was lowest for lambs born in May and July and highest for lambs born in September and November. When corrected to an average liveweight of 42 kg the average age was 230, 208, 176, 175, 245 and 236 days for lambs born in January, March, May, July, September and November respectively. These data suggest that lamb growth to these comparatively high slaughter weights was optimal when lambs were born in May and July. If premiums are offered for out-of-season production of heavy carcasses to supply the chilled meat trade, May appears to be the optimal time for lambing as the average slaughter date for this group was 27.10.87, compared to 12.01.88 for lambs born in July.

Early lambing in Hawkes Bay: Use of the ram effect - Muir PD; Smith NB; Wallace GJ (Proceedings of the New Zealand Society of Animal Production, 1989)
Three trials involving a total of 345 animals have been conducted in widely separated geographical regions in New Zealand, using a similar trial design to compare different treatment regimes for invermectin in beef weaners. Commencing at weaning and continuing into late winter/spring, trial animals received ivermectin subcutaneously at 200

Effect of active immunisation with follicular fluid on ovulation rates in Romney ewes - Henderson KM; Ellen RL; Weaver A; Ball K; McNatty KP (Proceedings of the New Zealand Society of Animal Production, 1989)
Twenty four beef carcasses, all visually graded as P1, were assigned on the basis of fat depth D, to fat classes L (n=5), P (n=7), K (n=8) and G (n=4). The percent dissected lean of these samples for each class was: L, 66.9; P, 64.6; K, 63.4; G, 60.7, while total dissected fat % was: L, 14.5; P, 17.3; K, 19.0 and G, 21.8. There were no significant differences in chemical composition of individual joints across fat classes, but there were highly significant differences between joints. Percent intramuscular fat content of the lean was: topside, 5.0; chuck, 7.5; loin, 12.1 and brisket, 12.4. Overall acceptability of the cooked loin was similar for all fat classes, despite a range from 4 to 24% in intramuscular fat content. There was not significant association between intramuscular fat and eating quality, which suggests that if pre- and post-slaughter conditions are well controlled, meat of satisfactory eating quality can be obtained from lean carcasses.

Effect of different ivermectin treatments on weight gains in beef weaners - McPherson WB; Cairns GC; Leaning WHD; Newcomb KM (Proceedings of the New Zealand Society of Animal Production, 1989)
Detailed sward measurements made before and after grazing can detect the changes in mass and composition of vertical sward horizons which result from grazing. When animal species are grazed in mixtures, it is impossible, by this method to relate such sward changes to any one particular species. We estimated that quantitative importance of different sward horizons to the diet of cattle (CA), sheep (SA) and goats (GA) grazing alone or in a mixture; cattle with sheep (CS), sheep with cattle (SC) and cattle with goats (CG), goats with cattle (GC) in a progressive defoliation of ryegrass/white clover pasture. A least squares optimisation routine estimated the contribution of 5, 40mm sward horizons, each containing 6 botanical components to oesphageal extrusa (OE), containing the same 6 components, from each of the treatments. The results suggest that the diet of CA was more equally derived from horizons above 40mm than was that of SA which was concentrated in the 80- 120mm horizon. GA was intermediate. The contribution of the upper sward horizons to the CS diet was greater than for CA and SC moved lower down the sward horizons than SA. The mixing of goats and cattle had less effect on the relative contribution of the sward horizons to the diet selected than mixing sheep and cattle.

The effect of exogenous melatonin, administered in summer, on wool growth and testis diameter of Romneys - Harris PM; Xu ZZ; Blair HT; Dellow DW; McCutcheon SN; Cockrem J (Proceedings of the New Zealand Society of Animal Production, 1989)
The expansion of molecular biology across most biological fields has meant an increasing application of this technology to agriculture. One of the most exciting new areas to emerge has been that of transgenic animal production. Genes, from a variety of sources, can be incorporated into the early embryo and therefore effectively alter the genotype, and even the physiology of an animal. Most of the work has been conducted using the laboratory mouse. Translation of the technology to the domestic animal has not met with great success, partly because of the genes and promoters chosen and partly because of the difficulty and expense in obtaining large numbers of suitable early embryos for gene incorporation. An efficient gene incorporation system is cow embryos ideally requires the development of a number of novel embryological techniques. They include in vitro maturation and fertilisation of bovine oocytes from abattoir- sourced ovaries, in-vitro culture to allow the development of fertilised embryos to readily transferable stages, satisfactory techniques for incorporating genes into the embryo and techniques such as embryonic cloning to exploit the transgenic cattle produced. The various techniques, their problems and successes are described in depth in this paper. A research programme has been initiated to link embryology, dairy science and molecular biology techniques with the aim of producing transgenic cattle with modified milk composition.

The effect of integrated grazing of goats, sheep and cattle on animal productivity and health on high-producing hill country pastures - Bown MD; McCall DG; Scott ML; Watson TG; Dow BW (Proceedings of the New Zealand Society of Animal Production, 1989)
A selection experiment at Waikite (Rotorua) began in 1971 with closed Angus herds selected for adjusted 13-month weight (AS1), adjusted 18-month weight (AS2) or with random replacement (ACO). A closed Hereford herd, selected for adjusted 13-month eight (HS1), was also established. At both 13 and 18 months of age, annual responses in live weight in the AS1, HS1 and AS2 herds averaged 0.96, 0.62 and 0.48% of the ACO herd means (calvings 1972-85). Five correlated responses were estimated. 1. Cow weight: From all ages of cows recorded over 4 seasons (on average 11 years of selection completed), AS1 and AS2 cows were 7.5 and 8.2% heavier respectively than ACO cows; HS1 cows were 2.5% heavier than AS1 cows, the same margin as in 1971. 2. Maternal weaning weight: (AS1 and AS2 herds only, relative to ACO): responses was estimated in a tester herd from calvings in 1982-86. The maternal grandsires were selected AS1 and AS2 bulls born after almost 2 generations (6 years) of selection. The AS1 herd was superior by 8.6 kg (5.7%) and the AS2 herd by 2.2 kg (1.5%). 3. Scrotal circumference: From the 1982-85 crops, the AS1 and AS2 bulls had respectively 0.9 (P<0.01) and 0.3 cm larger circumferences at 13 months of age and 0.7 (P<0.01) and 0.4 cm below corresponding AS1 values. 4. Height at withers: AS1 and AS2 bulls from the 1981 calf crop were respectively 3.5 and 2.5 cm taller (P<0.05) than the ACO bulls; the HS1 bulls were 2.3 cm taller (P<0.05) than the AS1 bulls. 5. Food intake: Average intake of silage by Angus bulls from the 1980 and 1981 crops were 10.4% and 11.7% greater (P<0.01) for AS1 and AS2 than ACO cattle respectively. Expressed relative to body weight, there was no significant difference due to herd. The pooled regression of daily intake of dry matter on 18-month weight was 0.0091 kg/kg (P<0.05), with a correlation of 0.32. The correlations of pre-fasting plasma tryptophan and the fall in plasma tryptophan concentration with average previous intake were 0.50 and 0.41, for bulls fasted over a 48 h period.

Effect of liveweight gain or loss on lamb meat quality - Kirton AH; Thorrold BS; Mercer GJK (Proceedings of the New Zealand Society of Animal Production, 1989)
No abstract supplied

Effect of melatonin immunisation on liveweight gain of red deer - Duckworth JA; Barrell GK (Proceedings of the New Zealand Society of Animal Production, 1989)
The primary constraint to extended milking intervals of dairy cattle without loss of solids production is the storage capacity of the udder needed to accommodate the milk produced over the extended period. This constraint may be overcome by the production of more concentrated milk as the volume of production is a major determinant of udder capacity. The production of more concentrated milk is being explored by two approaches. The first exploits the natural variation in milk solids' concentration present in commercial dairy herds. The herd test records from LIC, NZDB were used to identify 2 groups of 19 high breeding index Jersey cows with either high or low milk solids content, which were subsequently established at Ruakura in June 1988 along with 19 high BI Friesians. Mean fat concentration in November 1988 was 6.61, 5.32, and 4.74 for high and low solids and Friesian groups respectively. Corresponding values for protein content were 4.34, 3.72 and 3.42%. Effective hours worth of udder capacity in October-November 1988 was 27.4, 24.8 and 22.9 hours for high solids, low solids and Friesian groups respectively. The second approach involves the use of recombinant DNA techniques to modify the expression of the a-lactalbumin gene, a key component in water secretion in milk. Alpha-lactalbumin, one of the major whey proteins and a component of the enzyme lactose synthetase, plays a major role in regulation and synthesis of lactose, which in turn is the major osmole of milk. Antisense RNA and RNA enzymes can be used for highly specific inhibition of gene expression. These gene blocking agents bind to the 'natural' mRNA and block translation of the message into a protein. An antisense RNA construct with RNA enzyme cleavage activity against the a-lactalbumin gene has been constructed and is currently under evaluation. This construct will be placed downstream to a mammary specific promoter region and inserted into the bovine genome by gene transfer techniques to produce a transgenic animal. These techniques have considerable potential as tools in physiological studies and for producing animals of superior genotypes.

The effect of pH on colour and drip loss of lamb chops thawed in air and CO2 - Moore VJ (Proceedings of the New Zealand Society of Animal Production, 1989)
Kidding and multiple kidding rates following artificial insemination (AI) either at the second oestrus after CIDR withdrawal or after vasectomised buck introduction to isolated does were compared in a factorial design. Other factors were a comparison of cervical and laparoscopic AI; Regulin melatonin implants 4 weeks before AI versus no implants; and once daily oestrus detection with AI 2-5 hours after detection versus twice daily oestrus detection with AI 9-18 hours after detection. AI was carried out from 6-14 April, 20-28 days after CIDR withdrawal or 6-14 days after buck introduction. Laparoscopic AI resulted in a high kidding rate (65%) than cervical AI (34%). Regulin implants resulted in a lower kidding rate (38%) than no implants (47%) but a higher multiple kidding rate (68% versus 50%). There was no effect of once versus twice daily oestrus detection on kidding rate. CIDR treatment led to a higher proportion of the does present being inseminated (98%) than buck introduction (88%) during the 9 day AI period, but had no effect on overall fecundity.

Effect of Regulin implants on spring fertility, lactation and down growth of cashmere does - Moore RW; Bigham ML; Staples LD (Proceedings of the New Zealand Society of Animal Production, 1989)
Ultrasonography has permitted close visualisation of follicular development in cattle and has revealed that three waves of follicles normally develop during the oestrous cycle. Follicle stimulating hormone is important for the recruitment of follicles but it is not known how the recruited follicles are selected to become dominant over other follicles and eventually to ovulate. Hypothalamic, pituitary and ovarian hormones are secreted and released episodically. During the luteal phase of the oestrous cycle, the negative feedback of progesterone prevents any rise in luteinising hormone (LH). As progesterone levels fall, LH increases, prompting an increase in oestradiol which triggers the ovulatory LH surge and behavioural oestrus. LH causes ovulation and luteinisation of follicular cells. Luteal phase progesterone may be responsible for later increases in prostaglandin F2a (PG)F2a, a luteolytic hormone in cattle and sheep which is transferred from the uterus, its site of synthesis, to the corpus luteum. Oestradiol and oxytocin, synthesised in the ovary, may be involved in regulation of uterine synthesis of PGF2a, hastening luteolysis. At this time it is not known how essential these two hormones are to the process of luteolysis. The discovery and synthesis of new ovarian hormones should permit superovulation to become a more exact and a less expensive procedure and for embryonic mortality to be reduced.

Effect of spraying pasture with fungicide on growth rates of grazing lambs in autumn and spring - Reid TC; Lauren DR (Proceedings of the New Zealand Society of Animal Production, 1989)
The hogget reproduction of 67 FF/F+ and 27 ++ (Booroola x Romney) x (Booroola x Perendale), 30 Waihora (WR) and 39 Marshall Romney (MR) hoggets was compared under 4 nutritional treatments. The September born ewe lambs were grazed from 6 January to 5 June at 4 different pasture allowances: 2, 4, 6, and 10 kg DM/ewe/d. Three allowances (2, 4, 10) were continued until 11 September, following this date all ewes grazed together. There were significant effects of allowance on the percentage of ewes tupped and pregnant. There was no effect of genotype on these fertility traits. The percentages of ewes lambing multiples/ewes lambing were FF/F+ 58, ++ 0, MR11, and WR 27. The percentages of lambs weaned/lambs born were similar: 72, 59, 77 and 79 respectively. The percentages of lambs weaned/ewes joined were 58, 26, 26, and 49 respectively.

The effect of the F gene on characteristics of Booroola x Romney ram sperm - Moore RW; Woolhouse JK; Wilson MC (Proceedings of the New Zealand Society of Animal Production, 1989)
Real-time (B-mode) and simple (A-mode) ultrasonic instruments were evaluated in 2 experiments to assess their potential for measuring carcass fat and muscle variables. In a third experiment, progeny of five Romney selection lines were ultrasonically scanned at regular intervals from 5 to 14 months of age to record backfat thickness (C), GR and the width (A) and depth (B) of the L. dorsi muscle. In the one calibration experiment where the Toshiba machine was used, the machine was found to be particularly appropriate for measuring GR depth achieving a weight adjusted partial correlation of 0.81 with the carcass measurement and repeatability of 0.86. Comparable figures for the AIDD scanner in two experiments averaged 0.75 and 0.82 respectively for C fat depth measurements. Prediction equations for the chemical carcass lipid content showed that including either C or GR ultrasonic fat depths provided significantly improved estimates over those using only live weight. The addition of ultrasonic muscle widths or depths provided little additional advantage. The ultrasonic C and GR measurements confirmed that the production index line, selected on an index comprising dam's number of lambs born and the animals own weaning and hogget fleece weight, was the leanest. The single trait line selected on dam's number of lambs born, was slightly leaner than the controls, while the hogget fleece weight line was similar to the control line. The ranking of the 100 day weight selection line was found to vary with year of birth measured, but on average was similar to the control line. In contrast no major differences were detected in muscle width or depth among any of the selection lines.

Effects of cold conditions on the oxygen consumption of shorn goats - Holmes CW; Clark DA (Proceedings of the New Zealand Society of Animal Production, 1989)
Visual culling of 16-month old Romney ewe hoggets without access to performance records was carried out by five different groups of farmers who had contributed rams to the Rotomahana Strain Trial. Reasons for culling decisions were recorded and then all ewes, including those 'culled', were retained and farmed as a single flock to compare lifetime performance of culled and selected ewe replacements. Each group of farmers put most of its culling emphasis on size (i.e. smaller sheep were culled), with varying culling emphasis on mouth structure, woolly faces and wool. Less than five percent of the culling emphasis was for foot structure or breed type. All groups of farmers were able to 'select' ewes that had subsequent performance (number of lambs weaning and wool weight produced) superior to their 'culled' group of ewes. There was about a two-fold range among breeders in the effectiveness of their culling in terms of economic returns for lambs weaned plus wool produced over three lambings. Evaluation of ewe production through to seven years of age showed that the effects of visual culling on subsequently ewe performance were maintained over the lifetime of the ewe. The effect of 'culling' using performance traits in the same ewe hoggets as were subjected to visual culling was also assessed. Culling on most performance traits in the same ewe hoggets as were subjected to visual culling was also assessed. Culling on most performance traits was more effective than visual culling, resulting in up to 50% greater economic returns. Post-weaning body weights or fleece weights or a combination of these traits, were the most useful objective culling criteria.

Effects of melatonin on body weight, appetite and seasonal fur growth in the ferret - Pearson AJ; Ashby MG; Staples LD (Proceedings of the New Zealand Society of Animal Production, 1989)
A controlled internal drug release device, containing progesterone (CIDR-B), was evaluated as an aid to reproductive management in beef cattle in 2 trials. In Trial 1, 223 animals, comprising 64 early calving cows, 61 late calving cows, 59 maiden cows and 39 15-month heifers (yearling heifers), were treated intravaginally with CIDR-B for either 12d (plus 10mg oestradiol benzoate; 12d CIDR-B + ODB) or for 15d (15d CIDR-B). CIDRs were reused for 5d in half the animals from 16d after initial use. In Trial 2, 145 animals, comprising 53 early calving cows, 43 late calving cows and 49 15 month heifers, were treated intravaginally with CIDR-B for either 14d (14d CIDR-B) or 21d (21d CIDR-B). At CIDR-B withdrawal, half of the animals received an intra-muscular injection of 400IU PMSG. In Trial 1, within 48h of CIDR-B withdrawal, 58% and 54% of the animals were mated in the 15d CIDR-B and 12d CIDR-B + ODB groups respectively. Within 96h, the incidence of mating was 87% and 76% respectively with the difference between treatments being more pronounced in cows (88% v 74%; P<0.05) than in yearling heifers (86% v 84%). In cows, pregnancy rate to mating over the first 4 days was 50% in the 15d CIDR-B group and 67% in the 12d CIDR-B + ODB group (P<0.05). In yearlings, there was an opposite tendency (71% v 44%; P>0.1). Final pregnancy rate was 92% with no treatment group differences. CIDR-B ruse did not alter conception rates to first or second service but did synchronise returns. In Trial 2, within 4d of CIDR-B removal, 88% and 97% of the 14d CIDR-B and 21d CIDR-B groups had mated. In the 0 and 400 IU PMSG groups, 90% and 95% had mated. Pregnancy rate in treated animals to mating over the first 4 days following CIDR-B withdrawal were similar in the 14d CIDR-B and 21 CIDR-B groups (54% v 57%) and 0. and 400 IU PMSG groups (55% v 56%). However, pregnancy rate tended to be lower in yearling heifers compared to cows (46% v 57%; P>0.1). Final pregnancy rate tended to be higher in the 21d CIDR-B group than in the 14d CIDR-B group (89% v 82%; P>0.1). Fewer heifers were finally pregnant compared to early and late calving cows (74% v 85% v 95%). In both trials, longer CIDR-B treatment intervals were associated with earlier and more synchronised matings. Acceptable pregnancy rates were achieved with CIDR-B treatment intervals of between 12d and 21d. These results indicate that CIDR-B treatment without supplementary hormones can produce acceptable synchrony and fertility in naturally mated suckling beef cows and yearling heifers.

Effects of nutrition and shearing during pregnancy on birth weight in highly fecund Booroola-cross sheep - Orleans-Pobee J; Beatson PR (Proceedings of the New Zealand Society of Animal Production, 1989)
Current views and recent research findings on the plant characteristics influencing (a) herbage production and tolerance of grazing and (b) herbage intake and nutritive value, are reviewed and used to define desirable plant ideotypes for grazing systems. The conflict of interest between physical and physiological characteristics conferring high production and consumption potential on the one hand, and flexibility of production and grazing tolerance on the other, is emphasised. Current progress in and future prospects for the improvement of plants for grazing systems are discussed briefly, with reference to the potential for using mass selection and genetic engineering techniques in the modification of physical and biochemical characteristics. The need for objectivity in screening and evaluation programmes is discussed.

Effects of selection for shear strength on structure and rumen digestion of perennial ryegrass - John A; Inoue T; Brookes IM; Hunt WF; Easton HS (Proceedings of the New Zealand Society of Animal Production, 1989)
Lamb production from May or August lambing by Merino and Comeback ewes was compared from 1982 to 1985 in a factorial design experiment at Hamilton, Western Victoria. Groups of 50 ewes were stocked at 500 kg live weight/ha or 12.4 Merinos/ha and 10.8 Comebacks/ha. Natural fertility levels were similar for all treatments with an average of 5% ewes not lambing. Comeback ewes had a higher lambing rate (lambs born/ewes joined) at August compared with May lambing (1.28 v 1.19 sed 0.052) whereas the Merinos had similar lambing rates (1.03 v 1.07 sed 0.02), indicating that the Western Victorian Merinos were relatively insensitive to seasonal effects (photoperiod) on fecundity. Lamb mortality was higher at August compared with May lambing (18.5 v 14.5% sed 1.8%) and was associated with higher chill factors in August due to cooler, wetter weather. The effects of lamb mortality lead to similar weaning rates (lambs weaned/ewes joined) for Comebacks at May and August lambing and lower weaning rates for Merinos at August compared with May lambing. Lamb weaning weights were similar for both lambing times, except in 1985 when severe internal parasite infections before weaning in groups lambing in May restricted lamb growth. The lower stocking rate (ewes/ha) balanced the higher per head production for Comeback ewes and lead to no significant differences between breeds or lambing times in weight of lamb weaned per ha.

Effects of selection for shear strength on the voluntary intake and digestion of perennial ryegrass fed to sheep - Inoue T; Brookes IM; Barry TN; John A (Proceedings of the New Zealand Society of Animal Production, 1989)
Mature Romney ewes were involved in three experiments at Flock House Agricultural Centre and Limestone Downs (near Raglan) to identify factors affecting the percentage of ewes pregnant to mating in November and December following treatment with CIDRs and PMSG. Dorset rams were no better than Romney rams for mating and increasing the ram percentage from 10% to 15% failed to overcome the low conception rate of 50-65%. Rams that had been used for mating 11 days previously increased the percentage of ewes pregnant. Ewes previously lambing in autumn had only a 4.8% increase in ewes mated and pregnant compared with ewes previously lambing in spring. Despite the reuse of CIDRs reducing the percentage of ewes mated by 6.1% it was still economical to reuse CIDRs. There was a consistent increase in ewes pregnant and multiple pregnancies with increasing dose of PMSG. By contrast live weight had no effect on the reproductive performance of ewes except for those ewes less than 40 kg live weight. Regulin implants failed to overcome the low conception rate of ewes mating following treatment with CIDRs and PMSG in December.

Efficacy of Coprin in deer and sheep: An evaluation and comparative study - Harrison TJ; Sykes AR; Familton AS (Proceedings of the New Zealand Society of Animal Production, 1989)
The effect of treatment with melatonin (Regulin(r)) implants on spring down growth, oestrus and conception rates was examined in dry does (n=84), while the effect of this treatment on down growth, lactation and kid growth rates was examined lactating does (n=109). Treated does were implanted 3 times at 8 weekly intervals starting in early September. The animals were shorn and fleeces sampled on 26 January. Regulin(r) melatonin treatment increased down weight by 43%, 92% and 88% in dry hoggets, dry mixed-age and lactating mixed-age does, respectively, and increased down diameter by 6%, 2% and 4% and total fleece weight by 22%, 29% and 30% respectively. The down weight of the untreated lactating does (12.3g) was half that of the untreated dry does (24.3g). The lactating mixed-age does kidded from 30 August to 29 September, 4 does kidded before the first implant. Regulin(r) treatment had no effect on the appearance of milk secretions or the weaning weight of kids. Fertile bucks were joined from 6 October to 20 October and from 24 November to 8 December to the dry does. There was 1 mating mark and pregnancy in the treated does in the first joining period and no mating marks in either groups in the second period.

Estimates of environmental effects and genetic parameters for live weights and fleece traits of Angora goats - Nicoll GB; Bigham ML; Alderton MJ (Proceedings of the New Zealand Society of Animal Production, 1989)
Low voluntary intake and animal performance with perennial ryegrass has been attributed to its high leaf strength. Perennial ryegrass populations were selected for high or low shear strength and individual plants of low (LS) and high (HS) selections grown in a controlled environment. Shear strength of LS leaves (290 g) was half that of HS leaves. LS leaves were shorter, narrower and lighter. However, shear strength of LS remained significantly lower after adjustment for differences in leaf width. Shear strength in both selections declined from leaf base to leaf tip. LS leaves contained less sclerenchyma but had similar vascular tissue content. Sclerenchyma was significantly correlated with shear strength (r=0.82). Chopped leaves (5 cm) from both selections, placed in polyester bags were subjected to rumen microbial digestion. The higher shear strength of HS selected plants was maintained for at least 24 h rumen digestion. It is concluded that lower shear strength was a result of decreased sclerenchyma content and that potential improvements arising from easier breakdown would be maintained during rumen digestion in vivo.

Fibre growth cycles of unselected, reproducing cashmere does discussed in relation to winter shearing - Mitchell RJ; Betteridge K; Welch RAS; Gurnsey MP; Nixon AJ (Proceedings of the New Zealand Society of Animal Production, 1989)
Animalplan is an integrated set of data processing packages that meets the pedigree and performance recording requirements of many animal species in a unified way. The package offers much flexibility in terms of specification of breeding objectives, the traits to be recorded and presentation of reports. Technical aspects discussed include breeding objectives, trait adjustment for non-genetic effects using standard or flock/herd specific adjustments, prediction of breeding values using selection index techniques, restricting a trait to zero genetic change and the estimation of direct and maternal effects.

The growth of lambs throughout the year in the Waikato - Cruickshank GJ; Smith JF (Proceedings of the New Zealand Society of Animal Production, 1989)
No abstract supplied

Induction of twin ovulations in red deer hinds with steroid-free bovine follicular fluid - Fisher MW; Fennessy PF; Henderson KM; Newman RE; Manley TR (Proceedings of the New Zealand Society of Animal Production, 1989)
Because the enzyme catalase is involved in the peroxisomal pathway of fatty acid oxidation in the liver, it is possible that higher levels of catalase activity may be associated with higher levels of fatness. This was investigated in the high and low backfat Southdown sheep selection lines at Massey University. Liver biopsies were taken from 13 high backfat (HBD) and 14 low backfat (LBD) ewe hoggets with mean liveweight-adjusted ultrasonic backfat depths (LABF, expressed as percentage deviations) of +42% and -20% respectively. The HBD group had significantly higher (P<0.05) liver catalase activity (1944

The influence of sward height on the mechanics of grazing in steers and bulls - Mursan A; Hughes TP; Nicol AM; Sugiura T (Proceedings of the New Zealand Society of Animal Production, 1989)
A low cost system for producing early lambs is desirable both to capitalise on Hawkes Bay's climatic advantage of a mild winter and to minimise the feed deficit that results from a dry summer. A series of trials was undertaken to develop a system for using the "ram" effect to stimulate early oestrus (December/January) in otherwise anoestrous Romney ewes. When Poll Dorset rams (5%) and oestrous Poll Dorset ewes (10%) were joined with Romney ewes in early December, more ewes were mated after 3 cycles than when Poll Dorset rams alone were joined. The effectiveness of social facilitation appeared to vary between years with between 39 and 97% of Romney ewes mated after 3 cycles to an early December joining. The social facilitation effect also appeared to be less marked at a January joining. Romney ewes with a range of lambing rates from May to September and mean lactation periods of 12 weeks were weaned at varying intervals (12. 6 and 0 weeks) prior to ram introduction in early December. There was no difference in rate of onset of oestrus. Mean lambing dates for 90% of the ewes in the 3 groups were 18th, 12th and 10th June, respectively. There was no effect of live weight or body condition on date of first oestrus. Romney ewes were exchanged between Hawkes Bay and Wanganui to examine the effect of genotype and environment on the onset of oestrus. Poll Dorset rams (6%) were introduced on 30th November. By the 27th January 87% of ewes had been mated at the Hawkes Bay site compared with 15% at Wanganui. At each location there was little difference between ewes from the two sources in rate of onset of oestrus.

Inheritance of loose wool bulk - Sumner RMW; Clarke JN; Johnson DL (Proceedings of the New Zealand Society of Animal Production, 1989)
The digestive efficiency of deer, goats and sheep fed on chaffed lucerne hay was compared during summer (S) and winter (W). VFI, rumen pool size and rumen ammonia concentration showed seasonal cycles in red deer, with maximum values in S and minimum values in W, whereas rumen FOR showed lower values in S than in W, especially for particulate matter. Despite an increase in VFI, deer were thus able to maintain DM and fibre digestibility in S, due to simultaneously increasing rumen size and reducing outflow rate. Goats showed higher fibre digestibility relative to sheep, associated with a larger proportion of small particles in rumen digesta. Goats also had the highest rate of rumen ammonia production. Relative to goats and sheep, deer showed very low levels of VFI and rumen pool size in W, emphasising the importance of understanding the factors controlling winter inappetence in red deer, whilst the superior fibre digesting capability of goats suggests they could be most efficiently used to utilise low quality fibrous feeds.

Lamb production from Merino-type ewes lambing in May and August in Victoria - Thompson KF; Obst JM (Proceedings of the New Zealand Society of Animal Production, 1989)
An assortative breeding programme was carried out in 4 industry Perendale flocks and at Whatawhata using Cheviot, Perendale, Romney and Coopworth sheep. Within the industry flocks rams of high and low loose wool bulk were progeny tested. At Whatawhata Cheviot and Perendale rams of high, medium and low loose wool bulk were mated to ewes of equivalent bulk type within their own breed. High and low loose wool bulk Cheviot and Perendale rams and high loose wool bulk Romney rams were also mated to randomly allocated groups of Romney and Coopworth ewes. Progeny data provided an estimate of the phenotypic correlation between loose wool bulk measured at lamb and hogget shearing of 0.5. Breed effects on hogget loose wool bulk were essentially additive and complementary to the effects of sire selection within breeds. Statistical methods for evaluating heterogeneity of within-family variance of loose wool bulk at hogget shearing were used to investigate the possibility of a major gene influencing loose wool bulk. These methods could not confirm the hypothesis of a major gene controlling loose wool bulk. Offspring-parent relationships were consistent with previously published heritability estimates of around 0.5.

Lambing of Romney and Booroola cross hoggets with and without the F gene under different pasture allowances - Moore RW; McMillan WH; Dockrill G; Dow BW (Proceedings of the New Zealand Society of Animal Production, 1989)
Ruminants grazing pasture rarely approach their genetic potential for meat, milk or wool production. There are wide differences also between plant species and between leaf, stem and inflorescence fractions in their capacity to sustain animal production. The relatively low productivity of grazing ruminants and the differences between plant components in nutritional value can be explained from an understanding of the factors that determine nutrient supply to the animal's tissue and the efficiency of metabolism. Nutrient supply to the tissues depends on Ii) the nutrient contents of the forage available, which varies between plant species, their component parts, their stage of maturity and the growing conditions; (ii) the pasture components actually selected by the animal which are influenced by ease of eating, taste, odour and tactile characteristics of the plant material available, its water content, the structure of the sward, the dimensions of the animal's incisor arcade and its previous experience; (iii) the amount of each selected component eaten, which is influenced by the potential of the animal to utilize nutrients, the capacity of the reticulo-rumen and factors that affect the rate of digestion and outflow of organic matter from the rumen, and the time spent in eating and ruminating activities; (iv) modifications of consumed nutrients by rumen microbes, particularly the extent of breakdown of plant protein and the relative proportions of volatile fatty acids produced; (v) the efficiency of biochemical reactions metabolising the absorbed nutrients. Although a great deal is known about the way each of these factors influence nutrient supply to grazing animals, the complexity of the interactions between them often makes it extremely difficult to identify the specific reasons for reduced performance in any particular situation. However, by integrating current concepts and knowledge using computer simulation techniques, the factors limiting nutrients supply to the animal's tissues can be determined and the value of alternative management strategies for improving animal productivity assessed.

Liver catalase in Southdown sheep selected for high and low backfat depth - Peterson SW; Purchas RW (Proceedings of the New Zealand Society of Animal Production, 1989)
Four pairs of shorn Cashmere-type goats, fed at 1.5 x maintenance, were exposed to air temperatures between 5

Magnesium absorption from the large intestine of sheep - Dalley DE; Sykes AR (Proceedings of the New Zealand Society of Animal Production, 1989)
The proportions of ewes ovulating and ovulating multiples were recorded monthly from July-April in Poll Dorset ewes at 2 locations, and in Romney ewes at 4 locations. Flocks of 50-100 ewes were split into two groups and alternated from being isolated to being with vasectomised Dorset rams. Romney ewes differed between locations in ovarian activity even in July (83 and 56% ovulating in Levin and Ohakune). Romney ewes were anovular by September-October. By contrast, Poll Dorset ewes had a similar trend to ewes ovulating. Poll Dorset ewes at both locations returned to full ovarian activity between late December and January. In Romney ewes there were differences between locations in onset of ovarian activity, with the earliest location being Takapau, and Ohakune the latest. Onset of ovarian activity was 2-3 weeks earlier for teased than for isolated Romney ewes. The response to teasing at the end of the breeding season was small (12-15%) compared to the beginning of the season (44%). In a second experiment, 2500 mature Romney ewes were randomly allocated to two groups. One group was joined on 15 April and the other on 10 June. There were no differences in ewes lambing (96 v 97%) but multiple births declined from 44% for the early to 18% for the late joined ewes. This was partially offset by higher lamb survival in the later joined ewes (88 v 79%).

Mating Romney ewes in November-December using CIDRs and pregnant mare serum gonadotrophin - Knight TW; McMillan WH; Kannegieter SG; Sorensen ES; Ridland CJ; Gibb M (Proceedings of the New Zealand Society of Animal Production, 1989)
The policy on most New Zealand sheep farms is to pre-tup shear two tooths in late February/early March two to four weeks prior to mating. However, in summer-dry regions, where feed supplies are typically low in late summer, this practice may potentially depress two tooth performance because post-shearing increases in feed requirements cannot be met. An alternative hogget-four tooth shearing arrangement which does away with late summer/autumn two tooth shearing has therefore been investigated at Massey University's "Riverside" sheep farm in the Wairarapa; a farm prone to summer droughts. In trials over three years the alternative shearing arrangement was found not to disadvantage ewe liveweight gains, fertility, wool production or financial returns. In addition to reducing autumn feed requirements, earlier objective selection of flock replacements and hogget mating are potential benefits of the alternative shearing programme. A slightly poorer spring cashflow results but otherwise management requirements are similar.

Meat yields and chemical composition of muscle in New Zealand goats - Hogg BW; Catcheside LM; Mercer GJK; Duganzich DM (Proceedings of the New Zealand Society of Animal Production, 1989)
Three data sets comprising 2329, 2102, and 720 Angora goats sired by 30, 29 and 17 bucks used in the Land Corporation's Waitangi Angora flock, were used to obtain estimates of the effects of age, of dam, sex, rearing rank and birth day (age). Characters studied (and years of birth) in the three data sets were: Set 1: weaning weight and 12-month fleece weight (1978-1986); Set 2: 6-month fleece weight and yearling fleece weight (the sum of both 6- and 12-month fleece weights; 1978-1985); Set 3: 12-month live weight and 12-month fibre measurements of fibre diameter, standard deviation of fibre diameter, percent medullation and percent kemp (1984-1986). The weaning weights of kids out of dams aged 3, 4, 5 and 6 + years were heavier than those out of 2-year old dams by 0.7, 1.0, 1.5 and 1.8 kg respectively (P<0.001). Corresponding differences in 6-month fleece weight were 0.01, 0.02, 0.03 and 0.03 kg (P<0.05). Age-of-dam effects were variable for 12-month live weight and arcsine-transformed percent kemp, and nonsignificant for the remaining traits studied. Males had heavier live weights and fleece weights than females (P<0.001), but differences between the sexes were generally small for the fibre measurement traits. Multiple-reared kids (and later-born kids) had significantly lighter live weights and fleece weights than single-reared kids (and earlier-born kids). Both rearing rank and birth day effects were generally small and not significant for the fibre measurement traits. Heritability estimates for weaning weight, 6-, 12-month and yearling fleece weights, 12-month live weight, fibre diameter and standard deviation of fibre diameter were respectively 0.10, 0.24, 0.25, 0.36, 0.24, 0.51 and 0.21. Arcsine transformation of percent medullation and percent kemp data yielded heritabilities of 0.16 and 0.02 respectively. Subject to the limited number of sires represented in the data sets studied, genetic correlations between 12-month fleece weight and the two live weight traits were negative and of medium magnitude. There were also strong positive genetic correlations between 12-month fleece weight and both fibre diameter and arcsine- transformed percent kemp. Phenotypic correlations among live weight, fleece weight, and fibre diameter traits were all positive and of medium to high magnitude. Corresponding correlations with arcsine-transformed percents medullation and kemp were generally small and positive. It was concluded that direct incorporation of the genetic and phenotypic parameter estimates obtained in this study into selection index calculations, could not be advocated without due attention to the limited sample sizes and associated errors of estimation.

Multiple pregnancy diagnosis of ewes using real time ultrasonic body scanner and video-fluoroscopy systems - Grace ND; Beach AD; Quinlivan TD; Ward B (Proceedings of the New Zealand Society of Animal Production, 1989)
Eighteen entire male Saanen goats (liveweight range 5 to 115 kg; carcass weight range 2 to 52 kg; age range young to mature) and 19 female (liveweight range 17 to 64 kg; carcass weight range 8 to 32 kg age range several months to mature) were slaughtered. Carcasses were dissected into fat, muscle and bone. Based on allometric regression relationships an increase in carcass weight from 10 to 30 kg was accompanied by a decline in carcass muscle from 60.5 to 59.9% for the males, but from 61.8 to 51.5% for females. The greater decline in muscle content for the female carcasses reflected an increase in carcass fat content from 10.6 to 33.7%, while for male carcasses the increase was only from 11.7 to 15.5%. Over the same increase in carcass weight, carcass bone decreased from 24.7 to 14.1% for females, but only from 23.4 to 20.4% for males.

New Zealand - the sheep seed basket of the world - Binnie DB (Proceedings of the New Zealand Society of Animal Production, 1989)
Red deer calves (10 of each sex) were immunised at birth against a melatonin conjugate or injected with adjuvant only (10 of each sex). Booster injections were given on 5 occasions over the next two years and effects of immunisation on live-weight gain, pelage and reproductive changes were monitored throughout this period. Immunised stags were 7- 10% heavier than their controls between 9 and 11 months of age and at 16 and 20 months of age and a similar, but not significant, effect was recorded for immunised hinds. Immunisation did not affect calving date of the hinds, or casting date and time of stripping of the antlers in the stags or pelage changes in deer of either sex. These results indicate that immunisation of red deer against melatonin can modify the seasonal pattern of liveweight changes during their first two years of growth.

A note on the use of number of permanent incisor teeth for determining age in sheep - Bray AR; Burton RN; Murray MA; Saville DJ (Proceedings of the New Zealand Society of Animal Production, 1989)
Lambs in pens were infused duodenally with increasing amounts of casein or a mixture of four essential amino acids (EAA) to examine effects upon N retention. Eight Dorset Down x Coopworth lambs (39+/-1.1 kg) each fitted with rumen and duodenal cannulae were housed indoors and offered freshly cut ryegrass/white clover pasture at a rate of 470g fresh herbage/kgW0.75(MW)/d. The metabolizable energy intake from herbage was approximately 870 kJ/kg(MW)/d. Experimental treatments were duodenal infusions of water (control), 3, 6, 9 and 12g casein/kgMW/d and three levels of a mixture of AA (methionine, lysine, histidine and arginine) in amounts equivalent to the supply of these AA in 3, 6 and 9g casein. Treatments were allocated in an 8 x 8 latin square design. Duodenal non-ammonia N (NAN) flow indicated that 33% of forage protein N intake was lost across the rumen, the mean flow being 1.46gNAN/kgMW/d. Infusions of casein resulted in significant linear increases (P<0.01) in N balance up to 6g casein/kgMW/d, the casein N supply at this level being equal to the N lost across the rumen from the basal forage. The increase in N balance with infusion of 6g casein was equivalent to an additional 96% of the N balance observed with the control treatment. No further significant change in N balance was observed with casein infusions greater than 6g/kg/MW/d. A small non-significant response to infusions of 4 AA was observed indicating that these 4 essential AA were not solely responsible for the response. These results indicate that liveweight gain responses can be expected if the losses of protein that occur in the rumen of lambs grazing temperate pastures can be reduced.

Nutrition effects on live weight and reproduction of Cashmere doe hoggets - McCall DG; Clayton JB; Dow BW (Proceedings of the New Zealand Society of Animal Production, 1989)
Often effective breeding programmes are dependent on the assumption that heritabilities and genetic correlations between traits are the same in both sexes and that the genetic correlation for the same trait measured on both sexes is unity. A total of 12 302 records from 149 sire groups were analysed using mixed model techniques to test these assumptions. The results provide an indication that genetic and phenotypic parameters differ for male and female sheep. Cognizance of this fact should be taken when considering alternative selection strategies.