@conference {3729, title = {Farming within limits {\textendash} can system fundamentals be the key?}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {74}, year = {2014}, month = {06/2014}, pages = {241-244}, address = {Napier}, abstract = {The design of dairy systems with increased production and profit, but reduced environmental footprint, presents a problem with objectives that are seemingly at odds. We argue that this is why we have to go back to the ecological principles that underpin farm systems and use these to develop new systems that will achieve the above objectives. Healthy topsoil is a living nutrient trap. It requires long term thinking and action to achieve and maintain healthy topsoil. The rumen is a very complex ecosystem with the microbes as a key component. Farm systems aimed at optimal performance per cow, with lowest possible methane and urinary nitrogen waste products consistent with this performance, need to ensure effective rumen function. Maintenance dilution and cow longevity are important principles for sustainable and profitable farming. Pastoral livestock systems need ecological and financial buffers to remain resilient in uncertain times. We present a plan consisting of five strategies, based on some of these fundamentals, that we believe is a step towards farming profitably and within limits. }, issn = {1176-5283}, author = {Beukes PC and Romera AJ and Clark DA} } @conference {89220, title = {The changing nature of farm system research}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {73}, year = {2013}, month = {Jan}, pages = {54-64}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {

A personal review of the contribution of farm systems research to New Zealand pastoral agriculture. Case studies have been selected from the author{\textquoteright}s experience in sheep, dairy beef and dairy cow research over the past 40 years. These are used to emphasise the importance of progress in agricultural science and of wider societal concerns. The change in emphasis over time for farm systems research, from animal production per se, to production and profit, and now to production, profit and environmental protection is highlighted. Examples are also given of the value of thinking in a systems context in order to maximise the value of investment in basic and applied agricultural research.

}, issn = {1176-5283}, author = {Clark DA} } @conference {41801, title = {Jersey cows milked once-a-day can produce 1,200 kg milk solids per hectare}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {68}, year = {2008}, month = {Jan}, pages = {96-97}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Brisbane, Australia}, abstract = {While dairy cows are generally milked twice-a-day (TAD) in New Zealand, more farmers are adopting a once-a-day (OAD) milking routine to improve their lifestyle, reduce farm costs and improve animal welfare. Clark et al. (2006) reported that the yield of milksolids (MS) from Jersey cows was less affected (-19.9\%/cow) by OAD milking than the MS yield from Holstein-Friesian cows (-29.4\%/cow). Jersey cows milked OAD in Taranaki between 2000 and 2004 averaged 222 kg MS/cow and 979 kg MS/ha (Clark et al., 2006). In the 2006/07 season average per cow production from cows milked TAD in New Zealand was 330 kg MS ...Continued}, issn = {1176-5283}, author = {Dalley DE and Clough JW and Hofmann LA and Phyn CVC and Clark DA} } @conference {41555, title = {The effects of once a day milking on mastitis and somatic cell count}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {65}, year = {2005}, month = {Jan}, pages = {137-142}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {A four-year study examined the effect of once a day (OAD) milking for complete lactations on mastitis and milk quality. The study comprised two herds of Jersey cows and two of Friesian cows, milked either OAD or twice a day (TAD) for a total of 4 lactations. Prevalence of intramammary infection (IMI) was determined by isolation of mastitis pathogens from quarter foremilk samples, collected aseptically at calving, mid lactation and at drying off. In the second and third years of the study, at drying off, cows milked OAD had three times as many (P < 0.01) quarters with IMI by major mastitis pathogens compared with TAD cows. Across all pathogens and years however, prevalence of IMI was not significantly or consistently higher for cows milked OAD compared with TAD. The somatic cell count (SCC) for uninfected cows milked OAD was approximately double that for TAD milked cows although this difference was only significant (P < 0.05) after the first 1-2 months of lactation had elapsed. Cows with minor or major pathogen infections also showed an approximate doubling of the SCC if milked OAD. Results suggest that milking OAD consistently increases the individual cow SCC but does not significantly increase prevalence of mastitis. KEYWORDS: once daily milking; mastitis; SCC; milk quality; milking frequency. }, issn = {1176-5283}, author = {Lacy-Hulbert SJ and Dalley DE and Clark DA} } @conference {41851, title = {Feeding maize silage to dairy cows : implications for methane emissions}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {65}, year = {2005}, month = {Jan}, pages = {356-361}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {Maize silage was used on 25\% of New Zealand dairy farms in 2003/2004, with 26\% of these farms feeding 2 t DM/ha as maize silage. The nutritional value and animal responses to maize silage fed with pasture are well defined, but its impact on rumen methane emissions is not. In an 11-day indoor feeding trial, 32 Friesian dairy cows in mid lactation were fed ad libitum pasture with 0, 12, 24 and 36\% of the dry matter (DM) intake supplied by maize silage. Pasture and maize silage intakes, milk production and methane emissions were measured. Half of the cows in each treatment group were given intra-ruminal slow release monensin capsules. Total DM intakes were similar for all feed treatments. As maize silage intake increased, milksolids (MS) production decreased linearly from 1.73 (pasture only) to 1.46 kg/day (P = 0.0043, SED = 0.09) and methane emissions increased from 16.3 to 19.0 g/kg DMI (P = 0.0061, SED = 1.03). Increasing proportions of maize silage in a pasture-based diet increased methane emissions from lactating dairy cows. These effects were alleviated by monensin. KEYWORDS: dairy cows; methane emissions; milk production; perennial ryegrass; maize silage. }, issn = {1176-5283}, author = {Waugh CD and Clark DA and Waghorn GC and Woodward SL} } @conference {41852, title = {Impact of monensin on methane production and performance of cows fed forage diets}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {65}, year = {2005}, month = {Jan}, pages = {362-366}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {Monensin is an ionophore used to increase the efficiency of feed utilisation when grain-based rations are fed to beef cattle, but it can also lower energy losses to methane. A series of feeding experiments has been undertaken to measure the impact of monensin on methane production by dairy cows fed ryegrass-dominant pastures alone or with white clover, or maize silage. Methane production measured from 15 sets of identical twin cows fed indoors was reduced by 9\%, from 16.9 to 15.3 g/kg dry matter (DM; P < 0.01), and remained 10\% lower (P < 0.05) than Controls 72 days after the monensin capsule was given. When pasture was substituted with maize silage at 12, 24 and 36\% of DM intake, monensin reduced methane (g/kg DM) by 1, 6.5 and 10.5 \% respectively (P = 0.05). However, methane emissions were not affected in cows fed pasture with white clover at 15, 30 or 60\% of DM intake. Although monensin provides an important opportunity for methane reduction, the data demonstrate a need to understand reasons for variable responses to treatments under differing nutritional regimes. The added benefits of improved feed efficiency and reduced bloat suggest further investigation of monensin for forage fed ruminants is warranted. Keywords: monensin; dairy cows; methane; pasture; white clover; maize silage. }, issn = {1176-5283}, author = {Van Vugt SJ and Waghorn GC and Clark DA and Woodward SL} } @conference {41568, title = {Modelling dairy system efficiencies}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {65}, year = {2005}, month = {Jan}, pages = {203-208}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {The Dexcel Whole Farm Model (WFM) is being developed to simulate dairy systems based on the interaction of system components. The WFM was fitted against observed data from the Resource Efficient Dairying (RED) trial, Scott Farm, Hamilton (Treatment A, 2002/2003 season) and used to explore the effects of different stocking rates on measures of system efficiency, i.e. feed utilisation (FU) and feed conversion efficiency (FCE). At the same stocking rate as RED treatment A (3 cows/ha), and with the observed {\textquoteleft}bestpractice{\textquoteright} management principles in place, the WFM predicted a FU 7\% higher compared with the observed (73\% vs 66\%). Increasing stocking rate in the WFM resulted in an increase in FU, but the predicted FCE did not decrease as was expected. The model showed the importance of adhering to proven management principles to reduce feed wastage and thereby improve system efficiencies. Key words: stocking rate; simulation modelling; pasture utilisation; dairy farm. }, issn = {1176-5283}, author = {Jensen RN and Beukes PC and Clark DA and MacDonald KA} } @conference {41512, title = {Modelling farm systems with once-a-day milking}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {64}, year = {2004}, month = {Jan}, pages = {237-240}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {Our objectives were to investigate how a cow model, "Molly", deals with once-a-day milking and to use "Molly" in a Whole Farm Model to explore farm systems where once-a-day milking might produce results on a per hectare basis comparable to twice-a-day milking. We compared our model outputs to observed data from a Milking Frequency trial run by Dexcel at a research farm in Taranaki. Changing the rate constants for milk removal and degradation of the lactation hormone complex in "Molly" resulted in the model expressing the acute and chronic effects of once-a-day milking. The once-a-day cow model fed ad lib seasonal grass pasture showed a decrease in milksolids yield (kg/cow) of 31\% in Friesians compared to the observed 28\%. When we used .Molly. in the Whole Farm Model it showed that farm performance with once-a-day milking was 1135 kg milksolids/ha when a Friesian herd was stocked at 7\% higher and their lactation was extended by 14 days compared to a twice-a-day herd (1132 kg milksolids/ha). We conclude that farm performance with once-a-day milking is strongly dependent on selecting cows with higher lactational persistence under once-a-day milking and managing for extended lactations. }, issn = {1176-5283}, author = {Beukes PC and Thorrold BS and Wastney ME and Palliser CC and Clark DA} } @conference {41354, title = {Implementation of environmental regulations on-farm}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {62}, year = {2002}, month = {Jan}, pages = {219-224}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Palmerston North}, abstract = {

A case study of the consultative process concerning water clarity in Lake Taupo was used to identify the key elements required to reach consensus between land-owners, users and regulatory authorities. These elements included: the identification of all stakeholders; impacts at the farm level where individual behaviour change must occur; the scientific validity of data used and the decision support models available to assess biological and economic impacts. The importance of the consultative {\textquoteleft}process{\textquoteleft} itself and the need for sufficient time for this process to occur were other key elements. The Lake Taupo case study was then compared with the larger scale issue of greenhouse gas emissions (GHG) from New Zealand agriculture. We concluded that a much greater level of scientific uncertainty existed for the effect of GHG emissions on climate change than for Lake Taupo water clarity. This fact, coupled with the potentially much greater economic impacts on agriculture and individual farmers helped explain farmer reluctance to accept proposed solutions. Findings from the Lake Taupo study suggest the way forward in the GHG emission debate requires a major improvement in the underpinning science and a clearer understanding of the implications of GHG emission control at the farm scale. Mitigation options must consider both physical and financial inputs and outputs. The consultative process must involve farmers at policy, economic and science levels and be long enough to cover all issues.

}, issn = {1176-5283}, author = {Clark DA and Lambert MG} } @conference {41355, title = {Lactoferrin concentration is increased in milk from cows milked once daily}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {62}, year = {2002}, month = {Jan}, pages = {225-226}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Palmerston North}, abstract = {

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

}, issn = {1176-5283}, author = {Farr VC and Prosser CG and Clark DA and Tong M and Cooper CV and Willix-Payne D and Davis SR} } @conference {41228, title = {Effect on milk characteristics to supplementing cows on a restricted pasture allowance with different amounts of either turnips or sorghum}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {60}, year = {2000}, month = {Jan}, pages = {320-323}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {The effect of supplementary feeding 0, 4 or 8 kg DM/cow/d of turnips or sorghum to cows offered a restricted pasture allowance (25 kg DM/cow/d) on milk characteristics (fat, protein and lactose, N fractions, serum proteins, fatty acids (FAP) and solid fat content (SFC)) was investigated. Thirty identical twinsets were used (10 cows/treatment) in a partial cross-over designed experiment comprising two, 10-day periods. Sorghum was higher in fibre (NDF, 65\% v 23\%), total lipid (3.5\% v 1.5\%) and similar for crude protein (9.6\% v 12.0\%) than turnips. Lipid composition differed between crops; turnips had more lauric (C12:0) and less linolenic (C18:3) fatty acids than sorghum. Differences in the chemical composition of the crop were reflected in different milk compositions. Milkfat content was lower for cows fed turnips than sorghum and the effect was greater (P<0.001) with increasing amount of turnips fed (5.5\%, 5.1\% and 5.0\% for 0, 4, and 8 kg DM/cow/d respectively). Milkfat composition also differed for cows fed turnips compared to sorghum. With an increased amount of turnips fed, short, medium and long-chain fatty acids increased (P<0.001) and total unsaturated fatty acids decreased (P<0.001). As a consequence, SFC (an indication of milkfat hardness) also increased. Conjugated linoleic acid (cis-9- trans-11-C18:2) declined (P<0.001) as the level of supplementation with crop increased. The effect was greater (P<0.001) with turnips than sorghum. Compared with the fat components in milk the treatments had minimal effect on milk protein and nitrogen fractions. Feeding cows turnips compared to sorghum decreased (P<0.001) milk urea levels and increased (P<0.001) casein: whey protein ratio. This ratio declined (P<0.05) with increasing rates of supplementation with sorghum. These results show that different feed types can change milk components that influence the efficiency of milk processing, physical characteristics and nutritive value of the final dairy products. }, issn = {1176-5283}, author = {Thomson NA and Clark DA and Waugh CD and van der Poel WC and MacGibbon AKH} } @conference {41106, title = {Effect of Lotus corniculatus and condensed tannins on milk yield and composition of dairy cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {59}, year = {1999}, month = {Jan}, pages = {152-155}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Experiments at DRC have demonstrated birdsfoot trefoil (Lotus corniculatus) increases milk yield and milk protein concentra-tion of grazing dairy cows. An experiment was conducted in March 1998 to determine what proportion of the increased milk yield and milk protein\% was due to the condensed tannins (CT) in Lotus, and what proportion was due to factors typically associated with legumes (increased herbage intake and improved forage quality). Twenty Friesian cows were housed and fed twice daily on either perennial ryegrass or Lotus for 10 days. Five cows on each diet were also drenched with 1.2 l of 50\% polyethylene glycol (PEG) three times per day. PEG blocks the action of CT, preventing them binding to plant proteins. Milk yields (l/cow/d) were higher on Lotus (16.5) than on Lotus+PEG (13.8), ryegrass (10.2) or ryegrass+PEG (9.9) indicating that CT contributed to 42\% of the increased milk yield that resulted from feeding Lotus rather than ryegrass. CT had no effect on intake, since intakes (kgDM/cow/d) of cows fed Lotus (16.8) and Lotus+PEG (16.7) were similar and higher than for cows fed either ryegrass (14.7) or ryegrass+PEG (13.7). CT, however, accounted for all of the increase in herbage conversion efficiency as indicated by the higher efficiencies (ml FCM/MJ ME) of cows fed Lotus (147) compared with those fed Lotus+PEG (126), ryegrass (123) or ryegrass+PEG (127). CT accounted for 57\% of the increase in milk protein\% as cows fed Lotus (3.61) had higher protein\% than those fed Lotus+PEG (3.44), ryegrass (3.31) or ryegrass+PEG (3.30). Herbage or CT had no effect, however, on the casein or whey protein concentrations. CT had no effect on either milk fat or lactose concentration but cows fed Lotus had lower concentrations than cows fed ryegrass (P<0.05). Overall the trial showed legumes containing CT have potential as a forage for dairy cows.}, issn = {1176-5283}, author = {Woodward SL and Clark DA and Laboyrie PJ and Jansen EBL} } @conference {41135, title = {Milk production from perennial ryegrass pastures containing different levels of endophyte}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {59}, year = {1999}, month = {Jan}, pages = {258-262}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {These experiments aimed to compare milk production in spring and autumn from perennial ryegrass pastures containing either low (L) (<10\%) or high (H) levels of endophyte infection at two pasture allowances. In October 1997 milk yield was higher (P<0.05) from L compared with H endophyte (15.1 v 14.4 kg/cow/day), similarly for fat yield (0.95 v 0.9 kg/cow/day), and milksolids (MS) (1.53 v 1.46 kg/cow/day), but not protein yield. In October 1998 there was no effect of endophyte level on milk, fat, protein and MS yield. In March 1998 milk yield was higher (P<0.001) from H compared to L endophyte (8.5 v 7.4 kg/cow/day), similarly for fat yield (0.53 v 0.48 kg/cow/day), protein yield (0.35 v 0.34 kg/cow/day) and MS yield (0.89 v 0.81 kg/cow/day). No carryover effects were recorded on milk yield or composition in any period.}, issn = {1176-5283}, author = {Clark DA and Thom ER and Waugh CD and Burggraaf VT} } @conference {41006, title = {Use of {\textquoteright}Barkant{\textquoteright} turnips and {\textquoteright}Superchow{\textquoteright} sorghum crops to increase summer-autumn milk production}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {58}, year = {1998}, month = {Jan}, pages = {121-124}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {{\textquoteleft}Barkant{\textquoteleft} turnips and {\textquoteleft}Superchow{\textquoteleft} sorghum were compared as summer-autumn crops for lactating cows. Crops were fed at three levels (0, 4 and 8 kg DM/cow/d) to supplement pasture offered at a constant allowance. Sixty twin cows were used in two experimental periods in February and March 1997. Feeding 4 or 8 kg DM/cow/day increased milksolids (MS) yield/cow by 29\% or 36\% for turnips, and 26\% or 32\% for sorghum compared with pasture alone. Turnips gave responses of 58g and 45g MS/kg DM offered, at the lower allowance, in summer and autumn respectively, compared with 45g MS/kg DM in both seasons for sorghum. For both crops, increasing allowance from 4 to 8 kg further increased MS yield. Crop utilisation was lower on sorghum than turnips but substitution rates for turnips were higher than for sorghum at both allowances in both summer and autumn. This means that although both crops have a {\textquoteleft}pasture sparing{\textquoteleft} effect, sorghum contributed more to increased per cow intake. }, issn = {1176-5283}, author = {Harris SL and Clark DA and Waugh CD and Copeman PJA and Napper AR} } @conference {40827, title = {Dairy cow performance on limpograss (Hemarthria altissima)}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {56}, year = {1996}, month = {Jan}, pages = {245-250}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Limpograss is a perennial subtropical grass which has the potential to produce a bulk of standing feed (34 t DM/ha/yr) for consumption by cattle during summer. To assess the value of limpograss for lactating dairy cows, two experiments were conducted comparing limpograss and mixed temperate pasture diets. In both experiments a four day adjustment period was allowed before milksolids yield was assessed on three of the following ten days. Forage samples were taken for nutritional value assessment. During March 1994, two groups of six Friesian cows on once a day milking late in lactation were pen fed diets of freshly harvested limpograss (Hemarthria altissima) or temperate pasture at equal intakes of 13.1 }, issn = {1176-5283}, author = {Woods PW and Couchman JN and Clark DA} } @conference {40838, title = {Milk production from pastures and pasture silage with different levels of endophyte infection}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {56}, year = {1996}, month = {Jan}, pages = {292-296}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Perennial ryegrass (Lolium perenne L.) pastures in New Zealand contain the fungal endophyte (Acremonium lolii). This association produces a range of toxins; some, such as lolitrem B and ergovaline have been associated with ryegrass staggers, decreased serum prolactin, heat stress and decreased milk yield. Grazing trials with lactating cows have given equivocal results in terms of milksolids yield. Two experiments examined the effects on autumn milk production of supplementing cows grazing pasture with grass and grass/clover silages containing different endophyte concentrations on autumn milk production. Forty cows were used in a 2 x 2 factorial experiment with low (L) and high (H) levels of endophyte in both pasture and silage. In Experiment 1 (28 March - 6 April 1995) cows were grazing clover free pastures and supplemented with either L or H endophyte grass silage. In Experiment 2 (7-12 April 1995) cows were grazing pastures containing about 17-25\% white clover and supplemented with either L or H endophyte grass/clover silage. At the first milk sampling three days after treatments started in Experiment 1, milk yield from cows given L pastures was 6.9\% higher than from those grazing H endophyte pastures (P=0.006), and 4.1\% more when L rather than H endophyte silages were given (P=0.10). These effects were additive so the cows fed L endophyte silage and L endophyte pasture produced 11.3\% more than those fed H silage and H pasture (P=0.002). The effect of pasture endophyte on milk yield was still evident after seven and ten days of treatment, with 10.3\% more milk from L than from H endophyte pastures (P=0.01). Milk protein yields paralleled milk yields after seven and ten days but there was an endophyte x silage interaction (P=0.05) for milkfat yield and protein and fat yields were not effected by treatment. In Experiment 2 when clover was included in the diet there were no significant effects from either pasture or silage endophyte status on any milk yield components. A comparison of milksolids yield from Experiment 1 and Experiment 2 shows that changing to diets containing white clover increased milksolids by 6.4, 13.9 and 21.9\% for the L/L, L/H and H/L pasture/silage combinations, respectively, but only increased milksolids by 2.7\% for the H/H pasture/silage combination. We conclude that endophyte in both pasture and pasture silage can have a transitory effect on milk and protein yield during the autumn and the nutritional benefits of white clover for increasing milksolids was much reduced by endophyte in both pasture and silage diets. }, issn = {1176-5283}, author = {Clark DA and Thom ER and Waugh CD} } @conference {40572, title = {Some effects of feeding pasture silage as a supplement to pasture on reproductive performance in lactating dairy cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {54}, year = {1994}, month = {Jan}, pages = {95-98}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Supplementation of a ryegrass/white clover pasture diet with pasture silage is a common management practice in New Zealand dairy herds. The effect of this supplementation during early lactation on reproductive performance has not been investigated. Five herds of 20 cows were formed before calving commenced on June 1 1992. From August 5 to September 4, two of these herds were fed 5 kg dry matter/cow/day of pasture silage in addition to the ryegrass/white clover pasture offered to all herds. Pasture silage supplementation did not alter the intervals from calving to first ovulation, first oestrus, or to conception. However, it reduced the first service conception rate(37.5\% vs 53.3\%; (sed = {\textpm} 10.0\%), for pasture and silage and pasture only cows; respectively). A positive effect on reproductive performance of pasture silage supplementation was not demonstrated in this trial}, issn = {1176-5283}, author = {McDougall S and Clark DA and Macmillan KL and Williamson NB} } @conference {40303, title = {The effect of varying leafy sward height and bulk density on the ingestive behaviour of young deer and sheep}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {51}, year = {1991}, month = {Jan}, pages = {159-166}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {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. }, issn = {1176-5283}, author = {Mitchell RJ and Hodgson J and Clark DA} } @conference {40163, title = {Effects of cold conditions on the oxygen consumption of shorn goats}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {49}, year = {1989}, month = {Jan}, pages = {175-178}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {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 {\textquoteright}culled{\textquoteright}, 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 {\textquoteright}select{\textquoteright} ewes that had subsequent performance (number of lambs weaning and wool weight produced) superior to their {\textquoteright}culled{\textquoteright} 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 {\textquoteright}culling{\textquoteright} 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.}, issn = {1176-5283}, author = {Holmes CW and Clark DA} } @conference {39802, title = {Animal production from hill country: Effect of fertiliser and grazing management}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {42}, year = {1982}, month = {Jan}, pages = {173-176}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {In each of 2 years mixed age Coopworth ewes (1978, 58 kg; 1979, 55 kg) were randomised immediately before lambing and offered a range of herbage allowances (2, 4, 6, 8 and 10 kg DM ewe) from mixed pasture of contrasting mass (1978, 2300 v 4140; 1979, 2100 v 3600 kg/ha) and lucerne (1978, 4390 kg/ha; 1979, 3000 kg/ha) until weaning at 10 weeks post-lambing. Final ewe weight, weight change, weight of lamb weaned per ewe and ewe fleece weight all increased with allowance. Lamb weaning weights started to level off above 8 kg DM/ewe but ewe gains and fleece weight continued to increase. On the higher-mass pasture ewes were lighter in 1978 and lambs were lighter in 1979. Lucerne-fed ewes lost more weight and produced less wool, but had similar (1978) or heavier (1979) lambs at weaning than pasture-fed ewes. The importance of feeding during lactation on lamb weaning weight was highlighted and management implications discussed.}, issn = {1176-5283}, author = {Clark DA and Lambert MG} } @conference {39796, title = {Diet selection by goats and sheep on hill country}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {42}, year = {1982}, month = {Jan}, pages = {155-158}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Diet quality was measured using oesophageally-fistulated lactating Dorset ewes offered herbage allowances of 8 (H), 5 (M) and 2 (L) kg DM/ewe/d. Ewes on all allowances tended to have a similar selection preference for grass and clover; those on H and M allowances consumed proportionately more clover and less dead material than L ewes. The mean DDM of herbage selected by ewes in H and M groups averaged 0.790 and was 0.734 for L ewes compared with 0.727 for sward samples taken pre-grazing. The ME content of DM consumed by H and M ewes was 7\% greater than for L ewes. It is suggested that the lower digestibility of the diets of L ewes was due to a higher consumption of dead material and plant stalk than in ewes on H and M allowances.}, issn = {1176-5283}, author = {Clark DA and Lambert MG and Rolston MP and Dymock N} } @conference {39717, title = {Modelling a hill-country sheep production system}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {41}, year = {1981}, month = {Jan}, pages = {90-94}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, issn = {1176-5283}, author = {Field TRO and Clark DA and Lambert MG} } @conference {39648, title = {Feed intake of grazing Friesian bulls}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {39}, year = {1979}, month = {Jan}, pages = {265-274}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, issn = {1176-5283}, author = {Clark DA and Brougham RW} } @conference {39407, title = {Feed Conversion Efficiency in High Liveweight Gain and Low Liveweight Gain Friesian Bulls}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {33}, year = {1973}, month = {Jan}, pages = {206-207}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, issn = {1176-5283}, author = {Clark DA} }