@conference {3672, title = {Estimation of genetic parameters for milk yield traits at different herd production levels in cows milked once- or twice-daily in New Zealand}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {76}, year = {2016}, month = {07/2016}, pages = {49-53}, address = {Adelaide}, abstract = {The objective of this study was to estimate genetic parameters for lactation yields of milk (MY), fat (FY) and protein (PY) for cows milked either once- (OAD) or twice-a-day (TAD) at different production levels (PL), calculated as average milk solids yield (FY + PY) for dairy cattle in New Zealand. Lactation records of 124,620 and 194,631 cows from 298 and 350 herds milked OAD and TAD, respectively were used. Heritiabilities (h2) were lower in low PL herds milked OAD compared to low PL herds milked TAD (0.11-0.18 vs. 0.22-0.37). Across PL, h2 for MY at medium and high PL were greater than 0.30 at both MF, while for FY and PY, those values were less than 0.30. Genetic correlations (rG) between MY and PY were greater (>0.70) compared to rG between FY and any of the other traits (<0.65). The lowest rG was observed between MY and FY at low PL (0.09{\textpm}0.087). In conclusion, lower h2 at low PL from cows milked OAD reveal unequal genetic expression of milk traits genes compared to higher PL. Ignoring the heterogeneity of variance in the genetic evaluation could result in systematic inaccuracies and biases in the estimation of breeding values for cows milked OAD.}, issn = {1176-5283}, author = {Lembeye F and Lopez-Villalobos N and Burke JL and Davis SR} } @conference {3672, title = {Supply curves for yields of dairy products from first-lactation Holstein Friesian, Jersey and Holstein Friesian-Jersey crossbred cows accounting for seasonality of milk composition and production.}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {76}, year = {2016}, month = {07/2016}, pages = {139-143}, address = {Adelaide}, abstract = {The economic efficiency of a milk-processing system is influenced by seasonality of the milk supply, and changes to milk composition, influences the product potential of that milk. Lactation curves for milk yield and composition for seasonal calving first-lactation Holstein Friesian (F), Jersey (J) and Holstein Friesian-Jersey crossbred (FxJ) cows were used as inputs in a deterministic simulation model to produce seasonal curves for daily yields of dairy products. The dairy products were whole milk powder, skim milk powder, cheese, or butter. Dairy product potential was estimated for each animal from a population of 4333 mixed-breed, first-lactation cows. Lactation lengths differed (P<0.0001), among F, FxJ, and J, which averaged 219, 222 and 221 days respectively. Total-lactation milk yield was different (P<0.0001) among breeds and averaged 3257, 3092 and 2902 litres for F, FxJ and J cows, respectively. Whole-milk powder potential (yield per 1000 L of milk) was greatest at the start of the season and least at the end of the season, whereas cheese-production potential (yield per 1000 L of milk) followed the opposite pattern. Total-lactation whole-milk powder yield was different among breeds (P<0.0001) at 366, 338 and 312 kg of whole-milk powder for F, FxJ and J cows, respectively. Total-lactation cheese yield was also different among breeds (P<0.0001), and was 371, 375 and 361 kg for F, FxJ and J cows, respectively. The supply curves indicate that milk is best processed into whole or skim milk powder during peak season, and cheese and butter at the end of lactation. However, seasonal production of specific products would limit the use of by-product lactose from cheese manufacture in the production of milk powders, and thus negate the efficiency gains from changes to processing priorities.}, issn = {1176-5283}, author = {Sneddon NW and Lopez-Villalobos N and Davis SR and Hickson RE and Shalloo L and Garrick DJ} } @conference {3672, title = {BRIEF COMMUNICATION: Metabolite profiling in New Zealand milk}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {75}, year = {2015}, month = {07/2015}, pages = {39-41}, address = {Dunedin}, abstract = { }, issn = {1176-5283}, author = {Davis SR and Jaine J and Obolonkin V and Braggins TJ and Cooney TP and Scott A and Spelman RJ} } @conference {3672, title = {Estimation of breed and heterosis effects for milk traits and somatic cell scores in cows milked once and twice daily in New Zealand}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {75}, year = {2015}, month = {07/2015}, pages = {60-63}, address = {Dunedin}, abstract = { Crossbreeding is widely used by famers milking twice-a-day (TAD) to increase farm profitability. Effects of crossbreeding on farm productivity and profitability have not been investigated in farms practicing once-a-day (OAD) milking. The aim of the study was to estimate breed and heterosis effects for lactation length (LL), total yields of milk (MY), fat (FY) and protein (PY) and average somatic cell score (SCS) in cows milked OAD or TAD. Records from 36,276 Friesian (F), 31,560 Jersey (J) and 90,081 crossbred (F{\texttimes}J) cows that calved in spring between 2008 and 2012 were used. Compared to J cows, F cows had a higher MY (657 kg in OAD and 1034 kg in TAD), FY (2.9 kg in OAD and 7.8 kg in TAD), PY (13.6 kg in OAD and 22.4 kg in TAD) and SCS (0.28 in OAD and 0.05 TAD). Lactation length in OAD cows was five days shorter than in TAD cows (P<0.05). These results show a significant interaction between breed and milking frequency for production traits (P<0.001). Expressed as a percentage of the average of parental breeds, first-cross heterosis effects ranged between 4.92 to 6.84\% for production traits, and were similar across milking frequencies. The estimates of breed and heterosis obtained in this study can be used for simulation studies to evaluate the profitability of crossbreeding systems under OAD and TAD milking systems of typical New Zealand dairy farms.}, issn = {1176-5283}, author = {Lembeye F and Lopez-Villalobos N and Burke JL and Davis SR} } @conference {3678, title = {BRIEF COMMUNICATION: Milk production, live weight, body condition and somatic cell score during the first 150 days of lactation in Friesian, Jersey and crossbred cows milked once daily}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {74}, year = {2014}, month = {06/2014}, pages = {46-48}, address = {Napier}, abstract = {Pasture-based dairy farming in New Zealand has predominately been with cows milked twice a day (TAD). However, since the last decades, milking once a day (OAD) has been adopted by some farmers in New Zealand for herd management and lifestyle benefits (Davis 2005)...}, issn = {1176-5283}, author = {Lambeye F and Lopez-Villalobos N and Burke JL and Davis SR} } @conference {89235, title = {Insulin response to a glucose tolerance test in 18-month pregnant heifers as a predictor of subsequent survival}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {73}, year = {2013}, month = {Jan}, pages = {117-119}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {

A decline in dairy cow fertility in the USA and in the UK (Beam \& Butler 1999; Royal et al. 2000) has also been noted in New Zealand. Calving rate, the proportion of cows re-calving within the first 42 days of the subsequent seasonal calving period, in New Zealand decreased from approximately 70\% in 1991 to 60\% in 2004 (Harris et al. 2006). There has been no further deterioration in subsequent years.

}, issn = {1176-5283}, author = {Hutchinson KJ and Davis SR and MacKenzie DDS and Blair HT and McNaughton LR and Sanders K and Spelman RJ} } @conference {89246, title = {Quantitative trait loci associated with variation in maximum milk flow rate in Friesian -Jersey cross bred cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {73}, year = {2013}, month = {Jan}, pages = {168-170}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {

On New Zealand dairy farms, the milking process consumes more than half of the available labour hours (Jago et al. 2010). While some recent research has shown some potential to improve labour efficiency of dairy farms during milking (Jago et al. 2010), the speed of milking is, in large part, dictated by the slowest milking cows in the herd.

}, issn = {1176-5283}, author = {Davis SR and Littlejohn M and Ellison R and Spelman RJ} } @conference {75905, title = {Effect of lactation stage and breed on the concentration of unsaturated fatty acids in milkfat of New Zealand dairy cattle}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {71}, year = {2011}, month = {Jan}, pages = {203-207}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Invercargill}, abstract = {Milkfat composition influences the nutritional value and manufacturing characteristics of milk. This research studied the influence of: 1) stage of lactation on the concentration of unsaturated fatty acids (UFA) in milkfat of Holstein-Friesian, Jersey and Crossbred cows, 2) segregation of cows according to their UFA concentration in milkfat. The concentration of UFA in milkfat was predicted with a calibration equation using Fourier transform infrared spectroscopy. The data (21,757 test-day records) were analysed using a mixed model with a third-order orthogonal polynomial. In the three breeds studied, after early lactation the concentration of UFA in milkfat decreased steadily as the lactation progressed, but in Holstein-Friesian cows it increased slightly at the end of lactation. Throughout lactation, Holstein-Friesian cows produced milkfat with a higher concentration of UFA than Jersey and Crossbred cows. In each herd, cows were split into a high and a low group according to the average UFA concentration of the herd. The high UFA group had higher (P <0.001) milk yield, but lower (P <0.001) yields and concentrations of fat and protein than the low UFA group. This study indicates that concentration of UFA in milkfat is affected by breed and stage of lactation in New Zealand dairy cattle.}, issn = {1176-5283}, author = {Silva-Villacorta D and Lopez-Villalobos N and Blair HT and Hickson RE and Spelman RJ and Melis J and Davis SR and Berry SDK and Lehnert K and Snell RG} } @conference {69515, title = {Variation in feed conversion efficiency in Holstein-Friesian heifer calves}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {70}, year = {2010}, month = {Jun}, pages = {250-252}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Palmerston North}, abstract = {Feed conversion efficiency (FCE) is a measure of an animal{\textquoteright}s ability to convert feed into product and is a major determinant of profitability in livestock production. This study evaluated two determinants of FCE in Holstein-Friesian heifer calves, growth rate and residual feed intake (RFI). The improvement in FCE, measured as feed intake per unit of liveweight gain (kg/kg), associated with increased growth rate is well known (see Archer et al., 1999). It is measured when the energy costs of maintenance are relatively small compared to the energy intake that is partitioned into growth of animal tissues or lactation.}, issn = {1176-5283}, author = {Carnie KR and Davis SR and MacDonald KA and Waghorn GC and Obolonkin VV and Spelman RL} } @conference {60943, title = {Breed effects for lactoferrin concentration determined by Fourier transform infrared spectroscopy}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {69}, year = {2009}, month = {Jun}, pages = {60-64}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {A calibration equation based on partial least squares using Fourier transform infrared spectroscopy (FTIR) data was derived to predict concentration of lactoferrin (Lf) in bovine milk. The concordance correlation coefficient of the calibration equation was estimated at 0.81 using 246 milk samples collected in the 2003-04 season from second-parity crossbred cows during late lactation. The calibration equation was then used to predict the concentration of Lf (pLf) in 9,742 milk samples from 814 Holstein-Friesian (HF), 955 Jersey (J) and 842 crossbred HF x J cows sampled on average 3.7 times during the 2007-08 season. A repeatability animal model was used to obtain breed effects and estimates of variance components for pLf. Concentrations of pLF (mg/L milk) were significantly (P <0.001) different between breed groups (HF = 163 {\textpm} 3.8, HF x J = 175 {\textpm} 5.0 and J = 193 {\textpm} 6.3). Heritability and repeatability of pLf concentration were 0.16 {\textpm} 0.036 and 0.35 {\textpm} 0.012, respectively. These results confirm previous studies showing that Lf concentration in milk can be predicted using FTIR spectroscopy and that there are significant breed differences and animal variation that can be exploited in a breeding program. }, issn = {1176-5283}, author = {Lopez-Villalobos N and Davis SR and Beattie EM and Melis J and Berry S and Holroyd SE and Spelman RJ and Snell RG} } @conference {42057, title = {Testing for quantitative trait loci for lactation persistency in dairy cattle}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {68}, year = {2008}, month = {Jan}, pages = {107-110}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Brisbane, Australia}, abstract = {Lactational persistency has not been selected for in New Zealand dairy populations. Existing milk production data and pedigrees from New Zealand Holstein-Friesian cattle at pasture, recorded in the Livestock Improvement Corporation database were utilized with a grand-daughter design, for a genome-wide search for a quantitative trait locus for persistency of lactation. Persistency was defined as a weighted sum of test-day yields. A significant region was identified in one grandsire family on Chromosome 3 at microsatellite marker position AGLA247 (chromosomal position 67cM; P <0.05). To verify this result, data from a research dairy herd defining persistency as the mean of three weekly tests of daily yield in March (late lactation) divided by the equivalent daily yields in October (early lactation)) for three seasons beginning in 1997/98 were used in a phenotypic association study on Chromosome 3 only. One allele of marker HUJ246, close to the original region appeared to show an additive effect. The maximal difference between this genotype and the others at this marker locus was 12.3 {\textpm} 4.4\% of the mean persistency. The potential use of this marker in the New Zealand dairy cattle population depends on the current allele frequencies in the industry. }, issn = {1176-5283}, author = {Morris CA and Spelman RJ and Henderson HV and Cullen NG and Hyndman DL and Miller FM and Johnson DL and Molenaar AJ and Grigor MR and Davis SR} } @conference {41765, title = {Induced physical distension of rat mammary glands accelerates the onset of apoptosis and involution compared with milk accumulation alone : Brief Communication}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {67}, year = {2007}, month = {Jan}, pages = {403-406}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Wanaka}, abstract = {Extended periods of milk accumulation result in reduced milk secretion, increased apoptosis and eventually, involution of mammary glands. The subsequent change in epithelial cell shape from a cuboidal to a flattened morphology as the alveoli distend with milk may initiate changes in protein and gene expression (mechanotransduction) triggering the process of involution (Davis et al., 1999).}, issn = {1176-5283}, author = {Phyn CVC and Dobson JM and Davis SR and Stelwagen K and Singh K} } @conference {41903, title = {Effect of an extended milking interval on recovery of milk yield and somatic cell count in dairy cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {66}, year = {2006}, month = {Jan}, pages = {241-244}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Napier}, abstract = {The objective of the study was to determine whether lactation could be re-initiated after several days without milking. Thirty-six cows in mid lactation were subjected to a single period without milking of either 2, 4 or 7 days. Following these periods twice daily milking resumed. Two days after resumption of twice daily milking, milk yield was depressed to 92, 80 and 51\% of pre-treatment (twice a day milking) rates in the 2, 4 and 7-day treatments. The 2- and 4-d treatments achieved pre-treatment milk yields 3 and 4 days after the resumption of milking, respectively. The 7-d treatment failed to achieve pre-treatment yields in this time period. However, 6 days after the resumption of twice-daily milking there was no difference in average milk yield between the 3 groups. Following the resumption of milking, SCC exceeded 2 million cells/ml for the first day in all treatments. Within 3 days the SCC for the 2 and 4-day treatments were below the 400, 000 cells/ml penalty threshold. However, it took five days milking to achieve this level for the 7-day treatment. The results indicate that successful lactations can be re-established after up to 7 days without milking in mid-lactation, with minimal carry-over effects on milk yield for the rest of the lactation. }, issn = {1176-5283}, author = {Dalley DE and Davis SR} } @conference {41459, title = {Decreased gene expression of integrins in epithelial cells during mammary engorgement}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {64}, year = {2004}, month = {Jan}, pages = {11-13}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {In ruminants, the molecular mechanisms regulating mammary involution and apoptosis (programmed cell death) are not well characterised, but extensive research in rodents has established that many cell types, including mammary epithelial cells, require anchorage to the extracellular matrix for survival. This anchorage is mediated via the integrins, a family of transmembrane glycoproteins that bridge intra- and extracellular compartments enabling direct communication between adaptor molecules in the cytoplasm and specific receptor motifs on the ECM proteins (Clark \& Brugge, 1995; Giancotti \& Ruoslahti, 1999; Hynes, 1992). Integrins form heterodimers between α and β subunits to produce more than 20 different receptors, and many subtypes have been identified in mammary glands (Clark \& Brugge, 1995). We have shown previously that one such integrin, β1, is reduced rapidly as a result of induced weaning in rodents, and these changes are followed by apoptosis (McMahon et al., 2004). The aim of this study was to investigate the molecular mechanisms that may regulate mammary involution in the bovine by examining cell-matrix interactions that may be involved in survival of mammary epithelial cells, ultimately to improve lactational persistency and tolerance of extended milking intervals ... }, issn = {1176-5283}, author = {Singh K and Dobson J and Stelwagen K and Prosser CG and Farr VC and Molenaar A and Davis SR} } @conference {41469, title = {Expression of the tight junction protein zonula occludens-1 during mammary engorgement}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {64}, year = {2004}, month = {Jan}, pages = {43-47}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {An increase in tight junction (TJ) permeability occurs during extended milking intervals and is associated with reduced milk secretion. This paper examines temporal changes in the expression of a major TJ protein, zonula occludens-1 (ZO-1), during mammary engorgement. Alveolar mammary tissue was collected from 52 mid-lactation dairy heifers at 0, 6, 12, 18, 24, 36 and 72 h, and at 8 d following abrupt cessation of milking (n >= 6 cows per time point). ZO-1 protein expression significantly decreased during mammary engorgement (P<0.05). Similarly, ZO-1 mRNA expression had halved by 36 h to 8 d post-milking (P<0.05). In a second trial, alveolar tissue was collected from the udder halves of late-lactation dairy cows (n = 4) that were milked unilaterally, either once-daily or twice-daily for 4 days. A 1.7-fold increase in ZO-1 mRNA expression was detected after once-daily milking, compared with twice-daily milking (P<0.05). The down-regulation of ZO-1 during mammary engorgement is consistent with increased TJ permeability. However, the up-regulation of ZO-1 mRNA expression during short-term once-daily milking suggests that TJ function is repaired as the mammary gland adjusts to the extended milking interval. In conclusion, we have identified changes in ZO-1 critical to TJ function in bovine mammary glands. }, issn = {1176-5283}, author = {Cooper CV and Stelwagen K and Singh K and Farr VC and Prosser CG and Davis SR} } @conference {41457, title = {Northern analysis of temporal and spatial variation in milk protein expression during early mammary involution in dairy cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {64}, year = {2004}, month = {Jan}, pages = {5-7}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {Understanding the mammary responses that occur at the cessation of milking whether natural, forced, or which occur at the end of the milking season and during the subsequent initiation of mammary involution (Holst et al., 1987; Hurley, 1989) has relevance in milk production traits such as milk yield, persistency and extended milking intervals and may suggest ways of improving milk production in later lactation (Stelwagen, 2001) (Vetharaniam et al., 2003). The proportions of secretory, support and milk storage components vary significantly between the alveolar (main milk synthesis), peripheral (a several cm thick layer of secretory tissue surrounding the main alveolar bed) and cisternal (main milk storage area adjoining the teats) compartments of the udder (Farr et al., 1996; Sordillo and Nickerson, 1988; Weber, 1977). In addition, variations in the local proportions of these components has also been observed in the main alveolar areas and dramatic variations of gene expression depending on the local mammary tissue composition have been observed (Molenaar et al., 1992). Ignorance of the effect on gene expression profiles resulting from sampling variations could lead to improper interpretation of experimental results and hence there is a need for more extensive spatial and temporal surveys to be done. }, issn = {1176-5283}, author = {Molenaar AJ and Farr VC and Oden KE and Wheeler TT and McMahon CD and Good LL and Stelwagen K and Singh K and Davis SR} } @conference {41458, title = {The use of cDNA microarrays to investigate changes in gene expression in the involuting bovine mammary gland}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {64}, year = {2004}, month = {Jan}, pages = {8-10}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {The molecular mechanisms and pathways involved in involution of the udder and which coordinate and regulate the processes of cell death and proliferation after weaning/cessation of milking in ruminants, are poorly understood. The aim of this study was to use cDNA microarray analysis to identify genes and pathways involved in involution of the bovine mammary gland. Ultimately, because this process underpins lactation traits such as persistency and mammary responses to milking frequency (Stelwagen, 2001; Vetharaniam et al., 2003), this information may allow the development of novel strategies for improving milk production especially in the later stages of lactation. Involution of the bovine mammary gland was induced by abrupt termination of milking in 48 non-pregnant Friesian dairy cows at mid-lactation (average days in milk, 92 {\textpm} 3) {\textellipsis} }, issn = {1176-5283}, author = {Singh K and Molenaar AJ and Stelwagen K and Farr VC and Good L and Swanson K and Oden K and Wheeler T and McMahon C and Henderson H and Wilson T and Hyndman D and Baird D and McCulloch A and Davis SR} } @conference {41460, title = {The use of microarrays to investigate gene regulation in the bovine mammary gland during Streptococcus uberis mastitis}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {64}, year = {2004}, month = {Jan}, pages = {14-16}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {Bovine mastitis is one of the most costly dairy-based diseases worldwide with an estimated $60 M loss to New Zealand per season. Mastitis infections are a result of bacterial or fungal pathogens becoming established in the udder, and are detected by the increase of somatic cells in the mammary gland, bacteriology data and physical signs of infection. In New Zealand, mastitis is usually a result of a gram-positive bacterial infection (Brookbanks, 1966). Of these bacteria, Streptococcus uberis is emerging as one of the most prevalent causative organism of mastitis in New Zealand (McDougall, 2002). It resides naturally in the environment making prevention of the disease difficult. Currently the main means of controlling the disease is through administering antibiotics following identification of infection. The mammary gland is protected from invasion by the activation of non-specific (innate) and specific defence mechanisms. The innate immune response is the predominant defence during the early stages of infection and is induced rapidly at the site of infection (Sordillo et al., 1997). Although the local mammary innate immune response has been widely investigated, studies have focussed on known antibacterial compounds and little is known about the novel compounds in bovine milk and how these contribute to the defence system of the mammary gland. The mechanism by which the mammary gland innate immune system is active against S. uberis is poorly understood. By developing an understanding into the way S. uberis induces an immune response in the mammary gland and the effect of infection on mammary gland metabolism we may identify components which can be utilised to either reduce the symptoms of/or prevent or cure S. uberis mastitis. }, issn = {1176-5283}, author = {Swanson KM and Henderson HV and Farr VC and Davis SR and Oden K and Stelwagen K and Molenaar A and Singh K and Prosser CG} } @conference {41400, title = {The effects of insulin on the milk production of pasture-fed Jersey cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {63}, year = {2003}, month = {Jan}, pages = {35-39}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Queenstown}, abstract = {The aim of this experiment was to determine the effects of insulin on milk protein production in lactating, pasturefed dairy cows. Five lactating rumen-fistulated Jersey cows were subjected to a hyperinsulinaemic euglycaemic clamp (HEC) with and without an abomasal infusion of casein (310g/d) in a two period cross-over design experiment. The HEC significantly reduced milk yield in the control cows compared to casein-infused cows (9.9 {\textpm} 0.5 vs 13.2 {\textpm} 0.5 kg/d, P<0.001). Milk protein yield was significantly higher in the casein-infused cows compared to the control cows (482 {\textpm} 16 vs 421 {\textpm} 16 g/d, P<0.05). The HEC significantly reduced milk protein yield in the control cows compared to casein-infused cows (311 {\textpm} 16 vs 459 {\textpm} 16 g/d, P<0.001). The use of the HEC technique in pasture-fed cows did not result in the milk protein response reported in concentrate-fed cows. }, issn = {1176-5283}, author = {Back PJ and MacKenzie DDS and Davis SR and Harris PM and Lee J} } @conference {41305, title = {Increased milk lactic acid concentration is an early indicator of mastitis}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {62}, year = {2002}, month = {Jan}, pages = {22-23}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Palmerston North}, abstract = {The cost of mastitis to the dairy industry in NZ is substantial, with economic losses accruing from antibiotic costs, acute and chronic milk yield losses and reduced longevity of susceptible cows. Early detection and treatment of mastitis is a critical factor in reducing the severity of the infection and tissue damage within the udder (Douglas et al., 1997). However, increases in labour productivity are reducing contact time with cows, making early detection of mastitis increasingly difficult. In particular, the development of robotic milking equipment has highlighted the need for remote detection of mastitis. Apart from visual examination of fore-milk, somatic cell count (SCC) is used as the standard marker of milk quality. An increase in bulk milk SCC or a high SCC at herd test is used to diagnose new infections. However, one of the most widely used methods for cow-side or automated in-line testing for mastitis is the detection of changes in electrical conductivity of milk. This approach has several problems, not least of which is the limited accuracy of the method (see Woolford et al., 1998) and the relatively high cost of sensors (claws). The following study was undertaken as part of a screen of a number of potential markers in milk which could be used to indicate mastitis {\textellipsis} }, issn = {1176-5283}, author = {Farr VC and Prosser CG and Nicholas GD and Lee J and Hart AL and Davis SR} } @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 {41271, title = {Effects of insulin on amino acid uptake by the mammary gland of the pasture-fed lactating ruminant}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {61}, year = {2001}, month = {Jan}, pages = {144-147}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {Twelve lactating ewes housed indoors were allocated to one of two treatment groups (hyperinsulinaemic euglycaemic clamp (HEC) or control) in a randomised block design experiment. Mammary amino acid uptake from plasma and utilisation for milk protein synthesis was measured during the fourth day of the HEC using the arterio-venous concentration difference (A-V) technique. There was no change in milk protein output during the HEC (P>0.05). The HEC induced a significant decrease in arterial concentrations of all essential amino acids (EAA) except for histidine and an increase in the extraction efficiency of isoleucine (HEC, 61 {\textpm} 3\% vs. control, 52 {\textpm} 3\%, P<0.05) and leucine (HEC, 64 {\textpm} 3\% vs. control, 53 {\textpm} 3\%, P<0.05). There was no significant change in extraction efficiency of other EAA or mammary blood flow. The ratio of amino acid uptake from plasma to output in milk protein suggested deficits in uptake for some EAA in both treatments, especially histidine. These results indicate that the mammary gland can adapt to a changing arterial supply of amino acids to maintain milk protein output by increasing extraction efficiency and/or a greater reliance on amino acids supplied by erythrocytes and/or plasma peptides. }, issn = {1176-5283}, author = {Back PJ and Davis SR and MacKenzie DDS and Harris PM and Roy NC and Lee J} } @conference {41296, title = {Modelling the impact of milking frequency on lactation}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {61}, year = {2001}, month = {Jan}, pages = {239-240}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {Increasing milking frequency from the usual practice of twice-daily can enhance milk production and, thus, may be profitable in high-intensity dairy production systems. A decrease of milking frequency to once-daily decreases yield but may be used to alleviate nutritional stress, to conserve cow condition, or simply as a lifestyle choice. Published values in the literature indicate that reducing milking frequency from twice daily to once daily decreases yield by 7{\textemdash}34\%, and increasing milking frequency from twice daily to thrice daily increases yield by 7{\textemdash}20\% (Davis et al., 1999; Stelwagen, 2001). Additionally, milking frequency can influence the rate of decline in post-peak production in cows (Stelwagen, 2001). In order to further understand and quantify the manner in which milking frequency affects lactation, a mechanistic mathematical model of mammary function has been developed (Vetharaniam, Davis, Soboleva, Shorten \& Wake, Unpublished), based on mechanisms presented by Davis et al. (1999). As well as allowing analysis of the effect of milking frequency, this model also facilitated the exploration of some of the pathways through which nutrition influences mammary gland development (Davis et al. 2001). }, issn = {1176-5283}, author = {Vetharaniam I and Davis SR and Soboleva TK and Shorten PR and Wake GC} } @conference {41295, title = {Modelling the impact of nutrition and genotype on lactation}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {61}, year = {2001}, month = {Jan}, pages = {237-238}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {Dairy cows grazed on pasture experience variation in their nutritional status during lactation, as both pasture quality and availability vary seasonally. This has both immediate and long-term consequences on cow performance. Acute effects of nutrition are related to availability of nutrients for milk secretion, and are manifested in day-to-day variation in milk yields. Of further importance are the chronic effects of nutrition, which act on the development of the mammary gland, impacting on the persistency of lactation. Typically, cows in a New Zealand, pasture-grazing environment exhibit a decline in milk yield of around 10\% per month, after peak lactation, whereas cows fed a concentrate diet in Northern Hemisphere systems show declines of less than 4\%. Post-peak declines in milk yield are associated with a proportional and permanent decline in the number of secretory cells in the udder, and this decline is modulated by nutrition (Davis et al., 2000). Quantifying the milk-yield response of a cow to different nutritional regimes is useful from a breeding and selection point of view, but on its own does not give insight into which pathways are likely to be affected by nutrition, nor does it explain the origin of differences in responses between cows. To this end, mechanistic mathematical models that reflect the underlying biology of the udder are particularly useful. }, issn = {1176-5283}, author = {Davis SR and Vetharaniam I and Upsdell M and Kolver ES and Pleasants AB} } @conference {41298, title = {y-glutamyl transpeptidase and amino acid transport for milk protein production in vivo}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {61}, year = {2001}, month = {Jan}, pages = {244-247}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {Activity of the enzyme g-glutamyl transpeptidase (g-GT) (EC 2.3.2.2) a putative facilitator of amino acid (AA) transport in the mammary gland, increases before lactation and decreases at weaning, suggesting a role in AA transport for milk protein synthesis. The effect of g-GT inhibition by acivicin and supply of cyst(e)ine from N-acetylcysteine (NAC) on mammary AA uptake and milk production was studied in lactating goats. NAC increased (P<0.05) arterial supply of some AA but did not increase arterio-venous difference as a percentage of arterial supply (extraction \%) and did not alter milk protein yield. Acivicin decreased (P<0.05) milk protein yield but this effect was not found when NAC was administered in combination with acivicin. This indicates that NAC, by indirectly enhancing intracellular cysteine, countered the effect of acivicin inhibition, suggesting a role for g-GT in supply of cysteine for milk protein synthesis. }, issn = {1176-5283}, author = {Johnston SL and Roy NC and Davis SR and Tweedie JW and Kitson KE and Lee J} } @conference {41214, title = {Effects of diet on udder function and regression in Holstein-Friesian Cattle}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {60}, year = {2000}, month = {Jan}, pages = {275-276}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {The rate of decline in milk yield after peak lactation is about 10\% per month, for cows in New Zealand grazing pasture diets, and less than 4\% per month in concentrate-fed animals in northern hemisphere environments. Much of the decline in milk yield after peak lactation is associated with a similar proportional loss of secretory cells from the udder and, once lost, these cells cannot be replaced until the dry period before the next lactation. Thus, we have found (unpublished data) that from peak lactation (October) to late-lactation in New Zealand, there was a loss of over 50\% of mammary DNA. Such a loss was also reflected in changes in udder volume (Davis et al., 1985) and also in changes in milk storage capacity in the udder (Davis et al., 1987). Differences in lactational persistency between concentrate and pasture-fed animals suggest that nutrition exerts a long-term effect on milk production through maintenance of mammary secretory cell structures, as well as function. In the present experiment, our hypothesis was that cows fed concentrate diets would maintain milk production better than cows fed pasture over the summer months and that this would be reflected in the functional udder capacity (FUC). FUC is a measure of mammary cell numbers and is highly correlated with milk production (Davis et al., 1987). Further work attempted to correlate changes in FUC with concentrations of blood hormones sensitive to diet. }, issn = {1176-5283}, author = {Davis SR and Farr VC and Auldist MJ and Kolver ES} } @conference {41073, title = {Lack of effect of short term chromium supplementation in lactating Jersey cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {59}, year = {1999}, month = {Jan}, pages = {58-61}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {The responses of dairy cattle to chromium (Cr) supplementation reported in the literature suggest that it has the potential to reduce the incidence of both mastitis and ketosis. The effect of Cr supplementation of pasture fed dairy cows in early lactation was studied. Ten lactating Jersey cows fitted with rumen fistula were infused with either Cr-yeast (n=4), casein (n=3) or buffer only (controls; n=3) directly into the abomasum. All cows were subjected to a hyperinsulinaemic euglycaemic clamp. Preliminary results show that there was no effect of Cr supplementation on milk yield, cortisol and b-hydroxy butyrate concentrations and somatic cell counts. }, issn = {1176-5283}, author = {Back PJ and Lee J and MacKenzie DDS and Davis SR and Harris PM} } @conference {41030, title = {Amylin causes hypocalcaemia in lactating goats - Brief Communication}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {58}, year = {1998}, month = {Jan}, pages = {209-210}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Amylin is a 37-amino acid peptide, structurally related to calcitonin-gene-related peptide (CGRP), adrenomedullin and calcitonin (CT). It is co-secreted with insulin from the pancreatic {\ss}-cell. There is increasing evidence from rodent models that amylin may play an important role in the regulation of mineral metabolism, particularly Ca (Cooper, 1997). However, such a role has never been investigated in a ruminant model. The aim of this study was, therefore, to investigate a role for amylin in the regulation of Ca and metabolism of other minerals in lactating goats.}, issn = {1176-5283}, author = {Min SH and Farr VC and Lee J and Cooper GJS and Davis SR} } @conference {41025, title = {The effects of a cation-anion balanced diet on calcium and phosphorus metabolism in growing lambs}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {58}, year = {1998}, month = {Jan}, pages = {192-194}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {During the past decade, there has been renewed interest and research in the role of the dietary cation-anion balance (DCAB) in controlling Ca and P homeostasis. Two diets differing in DCAB (either high DCAB, 250 meq/kg DM, or low DCAB, -100 meq/kg DM) were fed to 10 Romney lambs. Feeding low DCAB decreased urine pH by 2.0 pH units; from 8.2 (SE=0.45) to 6.2 (SE=0.50), indicative of the anticipated changes in the ionic balance associated with alterations in the dietary CAB. Plasma concentrations of Ca and P, and whole-body Ca and P balance (intake-excretion) were similar for both groups of sheep. Reducing the dietary CAB caused a 7-fold increase in the urinary excretion of Ca (low DCAB 0.75 g/day vs high DCAB 0.11 g/day; P=0.001).The apparent absorption of Ca in the low DCAB and high DCAB groups were 1.6 and 1.3 g/day, respectively, although there was no significant difference between the two groups. These data indicate that lowering the DCAB increases urinary excretion of Ca of growing lambs without affecting Ca balance due to an alteration in the movement of Ca to and from bone. Similar changes in Ca absorption and utilisation have been observed in dairy cows, suggesting that the growing lamb is a suitable model for future studies in the regulation of Ca homeostasis in dairy cattle. }, issn = {1176-5283}, author = {Wilson KL and Min S and Revell DK and Lee J and MacKenzie DDS and Cottam YH and Davis SR} } @conference {41029, title = {The effects of Insulin-nutrient supply interactions on ewe lactation}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {58}, year = {1998}, month = {Jan}, pages = {205-208}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Six lactating abomasally cannulated ewes were subjected to a hyperinsulinemic euglycemic clamp with or without casein supplementation in a two period crossover design experiment. There was a significant response in milk (1169 {\textpm} 46 g/d vs 952 {\textpm} 46 g/d, P<0.001) and milk protein (66.4 g/d {\textpm} 2.7 g/d vs 54.2 g/d {\textpm} 2.7 g/d P<0.006), yield from casein supplemented ewes. There was no overall effect of the clamp on milk and milk protein yield, while the interaction was also non-significant. However, there was a significant reduction in feed intake (P<0.001) as the clamp continued, which may have compromised milk and milk protein response. There was also a significant period effect across all the measured parameters, which could also be a stage of lactation effect, due to the rapid decline of milk production during ewe lactation. In this study, in contrast to concentrate-fed cows, the utilisation of this technique did not increase milk protein yield in pasture fed lactating ewes. }, issn = {1176-5283}, author = {Back PJ and MacKenzie DDS and Davis SR and Harris PM} } @conference {40980, title = {Once-Daily Milking of Dairy Cows : An Appraisal}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {58}, year = {1998}, month = {Jan}, pages = {36-40}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Once-daily milking offers the opportunity for a quantum change in the operation of the dairy farm. In particular, once-daily milking provides the major opportunity to reduce costs and increase labour productivity. New Zealand cows (particularly Jerseys) already possess an advantage in favour of once daily milking - that they produce a relatively concentrated milk and therefore have the capacity to accumulate >24 hours-worth of milk production. Nevertheless, short-term trials indicate an average production loss of 21\% for once-daily relative to twice-daily milking. Full-lactation trials suggest greater losses of 35-50\%, although the productivity of commercial farms milking once-daily throughout lactation is consistent with much smaller losses. There is evidence that cows can adapt to longer milking intervals and this coupled with increased herd size and care to maximise milk removal may restrict yield losses on the farm to less than 10\%. Apart from the production loss, other negative consequences of once-daily milking include changes in milk composition, a reduction in milk processing quality and increased somatic cell count. Further, it is not known to what degree, if any, cow comfort is compromised by once-daily milking. If it becomes possible to identify more tolerant breeds or individuals, it may be feasible to reduce milk yield losses still further and ameliorate the changes in milk composition. }, issn = {1176-5283}, author = {Davis SR and Farr VC and Stelwagen K} } @conference {40983, title = {Rates of recovery of milk yield and composition following milking intervals of varying length}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {58}, year = {1998}, month = {Jan}, pages = {47-48}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {In order to examine the rate of recovery of milk yield and composition following an extended milking interval, 20 cows were milked out with the aid of oxytocin and subjected to single intervals of either 16, 24, 32 or 40h. Cows were then milked frequently with the aid of oxytocin during the subsequent 26h. Milk secretion rate was depressed to 67 and 56\% of pre-treatment (twice-daily milking) rates by the 32 and 40h treatments, and rates of recovery were slow, extending beyond 26h post-treatment. Milk fat and protein contents did not differ significantly among treatment groups while lactose content was reduced by the 32 and 40h intervals, recovering by 26h post-treatment. It was concluded that the udder is particularly sensitive to milk accumulation beyond 24h and that this leads to impairment of the {\textquoteleft}synthetic machinery{\textquoteright} in the udder. The prolonged effect on milk lactose concentrations with the longer intervals suggests that there was a sustained change in the integrity of tight junctions between secretory cells, leading to increased permeability of the mammary gland. Rates of recovery of yield and composition were relatively slow, taking >24h in spite of enhanced rates of milk removal. }, issn = {1176-5283}, author = {Farr VC and Stelwagen K and Davis SR} } @conference {40935, title = {Removal of cisternal milk following milk accumulation for 9 hours does not increase total yield during once-daily milking}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {57}, year = {1997}, month = {Jan}, pages = {217}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Once-daily milking (ODM) of dairy cows in New Zealand results in a yield loss of 15-25\% (Carruthers V.R. et al.,(1993)). This loss is not associated with the total storage capacity of the udder, although some studies have shown that increase in the volume of milk in the cistern is associated with reduced yield loss during ODM (Knight C.H. and Dewhurst R.J. (1994)). The following experi-ment was undertaken to determine whether removal of cisternal, but not alveolar milk, at the p.m. milking, de-creased the production loss during ODM.}, issn = {1176-5283}, author = {Farr VC and Davis SR and Stelwagen K} } @conference {40871, title = {Time to change{\textquoteright}}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {57}, year = {1997}, month = {Jan}, pages = {1-3}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {The topics discussed in the fifty-six Presidential ad-dresses preceding this one can be broadly categorised into those that are personal statements on personal research areas and those that are {\textquoteleft}tub-thumping{\textquoteright} about the Society or agricultural research in general. In recent times, Presidents Sykes ( 1986), Jury (1990) and Nicol (1992) have all thumped their tubs and exhorted the Society to change both in attitude and modus operandi. Alas, their exhortations have had little impact. They pointed the direction but we did not follow. So it is my intention to try again, for the simple reason that if we do not change, we will not survive as a Society, or maybe even as animal scientists. }, issn = {1176-5283}, author = {Davis SR} } @conference {40774, title = {Brief Communication: Effects of milk stasis and feed withdrawal on capillary exchange capacity in the goat mammary gland}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {56}, year = {1996}, month = {Jan}, pages = {49-50}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {The lactating mammary gland is critically dependent upon the provision of nutrients and hormonal stimuli from the blood to sustain milk synthesis. This is reflected in the high correlation between mammary arterial blood flow (F) and milk yield (MY). During established lactation in goats, frequent milking with oxytocin results in a higher blood flow to the mammary gland (Prosser and Davis, 1992). Conversely, MY and F decrease during both milk stasis (Stelwagen et al. 1994) and feed withdrawal (Davis and Collier, 1985). It has yet to be determined whether these decreases in the blood supply cause the decreases in MY or are as a result of a decrease in demand for blood by the secretory tissue.}, issn = {1176-5283}, author = {Farr VC and Davis SR and Prosser CG} } @conference {40773, title = {Brief Communication: The effect of somatostatin infusion on milk yield of goats}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {56}, year = {1996}, month = {Jan}, pages = {47-48}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Somatostatin is a hormone widely distributed among tissues which, depending upon species, will inhibit growth hormone release from the pituitary gland and modulate the release of insulin from the pancreas (e.g. Davis, 1975; Maglad et al.,1983). The physiological function of somatostatin in rumi-nants is largely unknown. Certainly effects of somatostatin on the function of the gastro-intestinal tract have been reported (Barry et al.,1985). However, somatostatin ap-pears not to modulate basal growth hormone release in ruminants (Davis, 1975). }, issn = {1176-5283}, author = {Davis SR and Farr VC and Myung KH and Prosser CG and Spencer GSG} } @conference {40782, title = {Measurement of cell death by in situ end labelling of ruminant mammary gland tissue}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {56}, year = {1996}, month = {Jan}, pages = {71-76}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Apoptosis was examined by in situ end labelling (ISEL) of DNA in ewe and cow mammary sections representing the cycle of mammary development, lactation and regression. Labelled nuclei, identifying apoptotic dying cells, were found in tissues from all developmental stages. Generally, apoptosis was low in tissue from virgin animals, moderate in 3 and low in 2 week udders from prepartum ewes and mid pregnant cows, moderate to high in udders from 1 week post partum ewe udders, moderate to low in lactating ewes and cows and slightly higher in involuting ewe and cow udders. Apoptosis was also generally higher in alveoli in stasis than in lactating alveoli. A dramatic finding was that there was intense labelling with both 35S and DIG in the lumenal contents of some alveoli in stasis/involution particularly with animals in later lactation. This suggested that there was a significant amount of ragged DNA ends in the lumen of these alveoli.}, issn = {1176-5283}, author = {Molenaar AJ and Wilkins RJ and Davis SR} } @conference {40792, title = {The role of the vagal innervation of the gut in insulin release in lactating ewes}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {56}, year = {1996}, month = {Jan}, pages = {110-113}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {The vagal innervation of the pancreas and upper gastrointestinal tract has been implicated in the release of insulin in response to hyperglycaemia in several mammalian species. Therefore the role of the vagal innervation of the abomasum and upper small intestine in the release of insulin and its effect on glucose metabolism was studied in lactating ewes because of the importance of glucose for milk synthesis and secretion in ruminants. Vagal fibres innervating the abomasum, pylorus and duodenum were sectioned in 3 lactating ewes (VAG); 3 control lactating ewes underwent sham- operations (SHAM). Seven and 14 days after the surgery, all animals were given an intravenous injection of glucose (100 mg/kg BW) and jugular blood samples collected for glucose and insulin determinations. Plasma glucose concentration (mean }, issn = {1176-5283}, author = {Herath CB and Reynolds GW and MacKenzie DDS and Davis SR and Harris PM} } @conference {40776, title = {Utilisation of methionine by the mammary gland of the lactating goat}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {56}, year = {1996}, month = {Jan}, pages = {53-57}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {The goat milk protein, a-lactalbumin, contains no methionine residues, hence if 35S label is supplied to the gland in the form of labelled methionine only, the appearance of 35S in a-lactalbumin gives a measure of transsulphuration of methionine to cysteine within the gland. Two lactating Saanen goats were surgically modified with catheters implanted in the mammary milk vein, femoral and external pudic mammary artery, and jugular vein to enable infusion of 35S-methionine, into either the whole body (jugular) or directly into the gland, and repetitive blood sampling. Specific radioactivity of methionine in the blood and milk proteins was determined at hourly intervals for 9 hours. Radioactivity of 35S was determined in a-lactalbumin when 35S-methionine was supplied directly to the gland via the mammary artery, but could not be detected when supplied via the jugular vein. Analysis of mammary tissue from the latter experiment did however show the appearance of 35S label in the intracellular cysteine pool which was derived from methionine. Both approaches suggested that transsulphuration within the gland, although small, may be important especially when supply of methionine to the gland is high. The fractional extraction of plasma methionine by the gland for two goats was 46.4}, issn = {1176-5283}, author = {Lee J and Treloar BP and Sinclair BR and Prosser CG and Davis SR and Harris PM} } @conference {40652, title = {Effect of once daily milking (ODM) on enzyme activities in the bovine mammary gland}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {55}, year = {1995}, month = {Jan}, pages = {12-13}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Maintenance diets containing two levels of energy (9.6 v. 11.5 MJME per kg DM) and two levels of protein (10.7 v.21.7 g nitrogen per kg DM) were fed to four groups, each of ten Romney (five low and five high staple tenacity) and four Drysdale yearling rams, for six weeks from mid March. Protein supplementation increased protein intake by 114\% (P<0.001). It increased clean wool growth in the treatment period (6.2 v. 10.2 g.um- 2.d-1, P<0.001), more so in Drysdales than Romneys (89 v. 46\%; P<0.001). It also increased mean fibre diameter (38.1 v. 34.3 um, P<0.001) without changing the proportion of fibre that was medullated. Responses to the nutrient supplements were similar in low and high staple tenacity Romney rams. It is concluded that during the photoperiod-induced decline in wool growth in autumn, sheep on a maintenance diet responded to the increase in dietary protein with an increase in the volume of fibre and volume of keratin produced with no net change in the proportion of fibre medullated. }, issn = {1176-5283}, author = {Farr VC and Stelwagen K and Kerr MA and Davis SR and Eichler SJ} } @conference {40650, title = {Effect of once-daily milking and bovine somatropin administration in Friesian cows on milk protease activity}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {55}, year = {1995}, month = {Jan}, pages = {7-8}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Samples of wool from Perendale hoggets born at Whatawhata Research Centre in 1989 from ewes selected for and against loose wool bulk were tested for propensity to yellow. After storage in a laboratory for two years, wool from the high bulk line was significantly more yellow than wool from low bulk line. When the greasy wool was incubated at 40 degrees and 100\% relative humidity, differences in all three tristimulus values between high and low bulk wool were significant. Tristimulus Y and Z decreased and Y minus Z increased when clean wool samples were subjected to more extreme challenges similar to those which may occur during processing. These changes did not affect the differences in colour between the selection lines. These results suggest that management changes may be required to restrict yellowing of high bulk wool during growth and storage. Simultaneous selection for reduced propensity to yellow and increased bulk may reduce the genetic progress attainable in either characteristic. }, issn = {1176-5283}, author = {Stelwagen K and Whyte JH and Zavizon B and Prosser CG and Davis SR and Farr VC and Politis I} } @conference {40653, title = {Nitric oxide and the control of mammary blood flow}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {55}, year = {1995}, month = {Jan}, pages = {14-16}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {This study monitored the behaviour of calves docked with a rubber ring with or without local anaesthesia. Forty five 3 to 4 month old Friesian heifer calves were divided equally into three groups viz control (C), docked following local anaesthetic (L). After treatment the calves were returned to a paddock where their behaviour was monitored continuously for 5 hours with scan sampling every 10 minutes. Standing, walking, grazing and ruminating behaviours were similar in the 3 groups. Within 30 minutes of the treatment tail shaking, and vocalization occurred in 10 and 5 R calves and of them 2 calves continued to tail shake and vocalise for a further 60 minutes. Tail shaking and vocalisation occurred in 7 and 5 of the L calves respectively at 150 minutes. Two of these calves vocalised at 180 minutes and one at 210 minutes following treatment. C calves did not shake their tails or vocalise. These observations suggest that milk distress was experienced by approximately two thirds of docked calves. }, issn = {1176-5283}, author = {Lacasse P and Farr VC and Davis SR and Prosser CG} } @conference {40649, title = {Partitioning of milk accumulation between cisternal and alveolar compartments of the bovine udder: relationship to production loss on once-daily milking}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {55}, year = {1995}, month = {Jan}, pages = {5-6}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Colour is an important characteristic affecting wool price. Canary yellow wool incidence is low in dry years but individuals can be classified according to their degreee of susceptibility to wool yellowing based on results of wool incubation test. Australian Merino, Corriedale and New Zealand Romney populations were tested. A number of 603, 1269 and 476 progenies and 21, 52 and 24 sires were used for these populations, respectively. Susceptibility to wool yellowing (YPC), greasy (GFW) and clean fleece weights (CFW), yield (Y) and mean fibre diameter (MFD) were analysed in a sire model. Heritability values for YPC were 0.21+/-0.11, 0.28+/-0.08 and 0.19+/- 0.07 for Merino, Corriedale and Romney, respectively. Genetic correlations between YPC and other traits were 0.04+/-0.31 with GFW, - 0.10+/-0.31 with CFW, -0.11+/-0.29 with Y and 0.51+/-0.29 with MFD for Merinos; 0.30+/-0.18, 0.17+/-0.19, -0.12+/-0.18 and 0.33+/-0.19, - 0.12+/-0.18 and 0.33+/-0.19 for Corriedale, respectively, and 0.77+/- 0.22, 0.44+/-0.31, -0.70+/-0.35 and 0.25+/-0.30 for Romney, respectively. Phenotypic correlations were negligible among this traits for these three populations, except for YPC and Y (-0.33+/-0.10). Selection strategies to reduce wool yellowing susceptibility will differ between genotypes. Low frequency of susceptible sheep in Merino population showed little justification for including YPC in genetic programmes for this particular breed only. }, issn = {1176-5283}, author = {Farr VC and Davis SR and Copeman PJA and Carruthers VR and Knight CH} } @conference {40654, title = {Regulation of lactose production by ovine mammary acini in culture}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {55}, year = {1995}, month = {Jan}, pages = {17-20}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Five sets of rising five year old Holstein-Friesian non-lactating identical twin cows were studied from February to April 1994. One member from each twin pair had been tail docked at 18 months of age while the other member had its tail intact. The animals were observed weekly at three different times of day; 7am, 12 noon and 3pm. At low fly levels there were no significant differences in the frequencies of either front (eg. leg stamping) or rear (eg. tail flicking) focused fly- induced behaviours between the two treatments. At high fly levels there were no significant differences in front focused behaviours but the docked animals performed significantly more rear focused behaviours than the non-docked cows (eg. 96 vs 34 tailflicks at 12 noon, p<0.05). The adrenocorticol responses to intravenous injection of 0.05mg ACTH (Synachthen, CIBA-GEIGY) or saline was assessed four times throughout the experiment. The animals were blood sampled at time - 1min, 50 and 120 min relative to the time of injection of ACTH or saline. There were no significant differences in plasma cortisol concentrations in response to ACTH injection between treatments. Tail docked cows had elevated levels of fly induced behaviour but did not have an altered adrenal cortex function. This suggests that behaviour is a more sensitive indicator of the effects of fly predation than adrenal response to ACTH. Sensitive physiological indicators of chronic stress need to be developed for the assessment of husbandry practices. }, issn = {1176-5283}, author = {McFadden TB and Callaghan MR and Davis SR} } @conference {40574, title = {Effect of once daily milking and concurrent somatotropin (bST) on production and mammary tight junction permeability in cows - Brief Communication}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {54}, year = {1994}, month = {Jan}, pages = {101-102}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {No abstract supplied }, issn = {1176-5283}, author = {Stelwagen K and Davis SR and Farr VC} } @conference {40580, title = {Relationships between major milk whey proteins in blood plasma and milk yield in dairy cattle.}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {54}, year = {1994}, month = {Jan}, pages = {121-124}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {We have examined the ability of co-cultured mouse mammary fat pad (MFP) to modulate the response of mouse mammary epithelial cells to a number of mitogens in vitro. In a series of 4 experiments, COMMA-1D cells were cultured with or without epithelium-free MFP obtained from the abdominal mammary glands of 23-day old virgin, female BALB/c mice. Final cell number was quantified as total DNA after 7 days. The main effect of MFP was significant in all experiments, MFP alone inducing a 6.1 to 8.2-fold increase in cell number relative to basal medium (BM) controls (P<0.001). Furthermore, this stimulatory effect of MFP synergised (P<0.02) with the mitogenic effect of 10\% foetal calf serum (FCS). Examination of the response to several mammogenic hormones indicated that insulin (10 ug/ml) alone did not increase cell number (P>0.05), and interacted with the effect of MFP (P<0.001). There was no effect of prolactin (2.5 ug/ml) either alone or with MFP, whereas hydrocortisone (2.5 ug/ml) attenuated the response to MFP (P<0.001). In the absence of MFP, insulin-like growth factor-I (IGF-I; 75 ng/ml) did not increase cell number (P>0.05), whilst epidermal growth factor (EGF; 25 ng/ml) significantly increased cell number 3.7-fold. Both of these growth factors markedly interacted with the effect of MFP (P<0.001). When cultured with the combination of these growth factors and MFP, the final cell number was 29.2 times that of BM alone (25.14 {\textpm} 0.84 vs 0.86 {\textpm} 0.12 ug DNA/well). There was no effect of prostaglandin E2 (PGE2; 0.5 ug/ml) or indomethacin (5 mg/ml), an inhibitor of prostaglandin synthesis, in the absence or presence of MFP. These findings demonstrate that a diffusible factor(s) from the MFP interacts with several regulators of mammary growth to markedly stimulate epithelial proliferation in vitro. Such a factor appears distinct from a number of classical mitogens, and may be involved in the regulation of mammary development in vivo. }, issn = {1176-5283}, author = {Morris CA and Davis SR and Eichler SJ and Cullen NG} } @conference {40575, title = {The utilisation of whole body cysteine by the mammary gland of the lactating goat}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {54}, year = {1994}, month = {Jan}, pages = {103-106}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Three lactating Saanen goats weighing 55-71 kg, producing 1.2-3.6 kg milk/day and fed ad libitum concentrates and hay, were infused via a jugular catheter with 35S-cysteine (35S-Cys) at 9.3 mCi/min for 9 hours. Blood samples were taken hourly and mammary tissue biopsied terminally. Concentrations and specific radioactivities (SRA) of cysteine (Cys) and glutathione (GSH) were determined in whole blood, plasma and mammary tissue. Mean arterial concentrations (nmoles/g{\textpm}SE) of Cys and GSH in whole blood, plasma and red blood cells were: 71{\textpm}7, 79{\textpm}9 and 19{\textpm}8; and 823{\textpm}30, 1.6{\textpm}01 and 3426{\textpm}124 respectively. Arterial SRA in whole blood at plateau (7-9h) of 35S-Cys (352{\textpm}13 dpm/nmole) was higher than that for GSH (5.9{\textpm}0.7 dpm/nmole). However the difference between intracellular SRA for Cys and GSH in mammary gland tissue was much less (231{\textpm}23 vs 146{\textpm}13 dpm/nmole). Total uptake of Cys by one half of the mammary gland was 0.5{\textpm}0.2 g/day. Whole body irreversible loss rate of Cys was 7.3{\textpm}0.7 g/day, giving a percentage utilisation of whole body Cys by the mammary gland of 13.6{\textpm}4.3. }, issn = {1176-5283}, author = {Knutson RJ and Lee J and Davis SR and Harris PM and MacKenzie DDS and McCutcheon SN} } @conference {40476, title = {An appraisal of the utility of primary cell culture from sheep udders to investigate the control of mammary function}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {53}, year = {1993}, month = {Jan}, pages = {151-154}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {No abstract supplied.}, issn = {1176-5283}, author = {Wheeler TT and Callaghan MR and Davis SR and Wilkins RJ} } @conference {40466, title = {Brief Communication - Differences in the concentrations of glucose and related metabolites in the milk of Jersey and Friesian cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {53}, year = {1993}, month = {Jan}, pages = {105-106}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {The objective of this study was to examine the effects of once daily milking (ODM) on yields of plasminogen, plasmin and other whey proteins and to investigate this possible role of plasmin in mammary gland involution. Twelve multiparous Friesian cows in the ninth month of lactation were placed on a ODM regimen for 7 days. Milk yields were determined and milk sampled for assay on the last day of twice daily milking (TDM) (day 1 of trial), days 3 and 7 of ODM (d4 \& d8) and again 7 days after return to TDM (d15). Data are expressed as least-square means for d1 (TDM) vs d4 (ODM) vs d8 (ODM) vs d15 (TDM) together with pooled SE (PSE). Once daily milking was associated with a significant (P<0.05) reduction in yields of milk, lactose, fat and total protein. The concentration of plasminogen increased during ODM (0.92 vs 1.52 vs 1.37 vs 0.95, PSE = 0.06 }, issn = {1176-5283}, author = {Eichler SJ and Davis SR} } @conference {40481, title = {Brief Communication - The nature of the microcirculation in the mammary gland of the lactating rat}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {53}, year = {1993}, month = {Jan}, pages = {171-172}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Of all farm production practices, intensive systems come under public scrutiny most, and intensive egg-production is often a particular source of concern. Caged hens are seen as unacceptable in most European countries due to the density of housing, barrenness of environment and restriction of "most normal behaviour patterns". In New Zealand most egg-production systems involve practices which are being questioned overseas in terms of their welfare impact. This paper presents the results of a survey of some representative New Zealand farms in the light of public and scientific concerns for animal welfare. Currently there appears to be no obvious system likely to replace laying cages and guarantee good welfare. Pressure for change, however, seems likely.}, issn = {1176-5283}, author = {Davis SR and Farr VC and Prosser CG and Thompson JG} } @conference {40478, title = {The effect of an extended milking interval on mammary blood flow and tight junctions between mammary cells in goats}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {53}, year = {1993}, month = {Jan}, pages = {159-162}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Hereford x Friesian cows were used to compare the calf and cow performance of 66 single-calved cows (Single Cows) rearing only their own calf (Single Calf) and 45 contemporary single-calved cows (Foster Cows) rearing their own calf (Own Calf) plus a foster calf (Foster Calf). Fostering was succesful in 85\% and 95\% of attempts in 1990 and 1991, respectively. Mean weaning weight was lowest in the Foster Calf group but comparable in the Own Claf and Single Calf groups (140 vs 194 vs 202 kg, P6cm, B, 3 to 6 cm, C, 0 to 3 cm) was studied using oesophageally fistulated ewes in summer and autumn. Green grass leaf (GGL) contributed 68 to 97\% of diets, whilst pseudostem and dead material were rejected. Sward and dietary white clover contents were low in the sward and 0.1 to 4.9\% in the diet) and no selection for this component was evident. Defoliation of white clover appeared to be influenced by the vertical distribution of GGL. Green material distribution determined the horizons grazed. Sheep grazed horizon C of summer ryegrass pasture, where 95\% of GGL was found. In all other swards the surface canopy (>3 cm above ground level) was composed primarily of GGL (>30\%), and sheep grazed this horizon. Low apparent intake (21 g DM/kg live weight/d) was associated with the apparent need to penetrate the surface canopy to obtain GGL in summer ryegrass pasture.}, issn = {1176-5283}, author = {Davis SR and Bass JJ} } @conference {39825, title = {Differences in the extent of mammary development between Jersey cows of high or low genetic merit - Brief Communication}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {43}, year = {1983}, month = {Jan}, pages = {71-72}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {The effect of feed allowance (approximately 150 and 250 g green DM/kg live weight 0.75/d) and season (sampling at 12-week intervals) on objectively measured wool characteristics of Cheviot, Drysdale and Romney hoggets was examined. Improved feeding increased wool growth rate, fibre diameter and brightness. Feeding level did not affect fibre diameter variation, loose wool bulk or yellowness. Wool grew faster and was coarser during summer than during winter. Fibre diameter variation for the Cheviot and Romney was greatest in winter and least for the Drysdale in summer. There was no defined seasonal cycle for loose wool bulk. Colour indices were related to prevailing weather conditions. Maximum and minimum values for each characteristic were strongly correlated for fibre diameter and fibre diameter variation, weakly correlated for loose wool bulk and not consistently related for wool growth rate and colour indices.}, issn = {1176-5283}, author = {Davis SR and Hughson GA and Bryant AM} } @conference {39799, title = {Blood plasma tryptophan concentration - a potentially useful indicator of feed intake in pasture-fed ruminants - Brief Communication}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {42}, year = {1982}, month = {Jan}, pages = {165-166}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Mixed perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) pastures at Ruakura were sprayed with Mefluidide, a herbage growth retardant, in 3 consecutive spring periods from 1978. Pasture DM yields was markedly depressed at rates as low as 0.2 kg ai/ha and the effects were more marked with early season applications than those applied in late season. Mefluidide reduced the incidence of Poa annua L. in the swards and white clover was increased. In 1979/80, weaned lambs were set stocked on pastures sprayed with Mefluidide at 0.2 kg ai./ha. Live-weight gain/head was increased at each of 3 levels of pasture on offer. Pastures again contained less Poa annua and more white clover. In 1980/1 pastures were sprayed with Mefluidide at 0.2 kg ai/ha Ethofumesate at 0.2 kg ai/ha to eliminate clovers. Lamb gain was again increased on pastures sprayed with Mefluidide although 1 month after application fewer animals were carried at equivalent levels of herbage offer, due to lower herbage growth rates. It is concluded that Mefluidide enhances the herbage quality of perennial ryegrass/white clover pasture and that the technique has special application where per head performance is of paramount importance.}, issn = {1176-5283}, author = {Davis SR and Hughson GA and McLeay LM} } @conference {39712, title = {The hormonal induction of lactation in dry dairy cows - Brief Communication}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {41}, year = {1981}, month = {Jan}, pages = {68-70}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, issn = {1176-5283}, author = {Davis SR and Welch RAS and Pearce MG and Peterson AJ} } @conference {39738, title = {Interrelationships of placental development with nutrition in pregnancy and lamb birth weight}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {41}, year = {1981}, month = {Jan}, pages = {218-223}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, issn = {1176-5283}, author = {Davis SR and Rattray PV and Petch ME and Duganzich DM} } @conference {39679, title = {The relationship between the degree of udder development and milk production in Coopworth ewes - Brief Communication}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {40}, year = {1980}, month = {Jan}, pages = {163-165}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, issn = {1176-5283}, author = {Davis SR and Hughson G and Farquhar PA and Rattray PV} }