@conference {40777, title = {Effects of stage of lactation and season on udder development and milk yield in pasture-fed cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {56}, year = {1996}, month = {Jan}, pages = {58-60}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Effects of stage of lactation and season on mammary development and milk yield were determined in three herds of lactating Friesian cows (n~25 cows/herd) during June and July 1995. The herds in early, mid or late lactation calved in Apr-95, Jan-95 or Oct-94, respectively. Milk yield, in June, was higher in early and mid than in late lactation (16.1, 15.3 and 11.7 kg/d respectively, P<0.001). In July, yield was highest in early lactation and significantly lower with each successive stage of lactation (14.0, 12.5 and 10.4 kg/d, P<0.02). Yield decreased from June to July (14.4 to 12.3 kg/day, P<0.001) under increasingly severe nutritional/environmental influences. Udder capacity was higher in early and mid lactation than in late (16.1, 16.2 and 14.3 L, P=0.07), and decreased 18\% from June to July (17.1 to 14.0 L, P<0.001). These results suggest that loss of mammary capacity is an important cause of declining milk production due to stage of lactation and season. }, issn = {1176-5283}, author = {Eichler SJ and McFadden TB} } @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 {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 {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 {40475, title = {Factors affecting the production of lactose by ovine mammary cells in vitro}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {53}, year = {1993}, month = {Jan}, pages = {147-150}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {The present public and scientific interest in the welfare of farm livestock has caused traditional management procedures, including castration, tail docking and dehorning, to be scrutinised as causes of stress (stressors). This laudable scientific endeavour is however subject to a range of constraints. Major constraints are the subjective nature of distress, and the consequent difficulty of identifying indices which can be used confidently to quantify it. Nevertheless, behavioural and physiological indices have been identified by comparison with human responses to aversive stimuli, and allow distress to be assessed in animals. Changes in plasma cortisol concentrations, reflecting the activity of the hypothalamic-pituitary-adrenal system, are commonly used as an index of distress in farm livestock exposed to stressors. Judged thus, the distress caused by castration or tail docking of sheep and cattle apparently depends on several factors including the procedure itself, the age of the animal, the method used, the species and possibly the prior method of rearing. Little is known about the distress caused by dehorning of cattle. Several factors can confound the assessment of distress. They are: (1) balancing the objectivity of the measured indices with subjective judgements about what are acceptable and unacceptable levels of distress; (2) ensuring that the parameters used do indeed reflect distress, and not other phenomena; (3) avoiding erroneous predictions, based on anthropocentric projections and not scientific observations, about expected distress levels in situations which have not yet been examined; and (4) meeting the high cost of rigorous studies in this complex area in which a wide range of factors may affect the outcome. Reducing the distress caused by castration, tail docking or dehorning may be achieved by choosing an age when the distress response is least, choosing the least distressing method, or using anaesthesia (local, general) or systemic analgesia. When a method is identified which causes the least distress, its widespread use on farms should not be recommended unless it is also practicable. To do so will not benefit either the livestock concerned or the industry. Political and trade pressures related to overseas perceptions of New Zealand animal welfare standards require responses based on rigorous scientific assessment. Those responses are likely to involve, as appropriate, vigorous defences of current practices or the adoption of new approaches.}, issn = {1176-5283}, author = {Davis SR and Eichler SJ and Callaghan MR and Grieve RCJ and Prosser CG} }