Lynch J M, Barbano D M, Bauman D E, Hartnell G F, Nemeth M A
Department of Food Science, Cornell University, Ithaca, NY 14853.
J Dairy Sci. 1992 Jul;75(7):1794-809. doi: 10.3168/jds.S0022-0302(92)77938-7.
Nine Holstein cows were injected bi-weekly with a prolonged-release formulation of N-methionyl bST, and 9 cows were injected with excipient. Intramuscular injections began at 60 +/- 3 d postpartum and continued at 14-d intervals for the full lactation. Administration of bST increased production of milk, total fat, and all milk fat components measured. Average fatty acid composition of milk fat was not influenced by bST treatment. Stage of lactation had a large influence on production and percentage of individual fatty acids in milk fat from both bST-treated and control cows. The stage of lactation impact on the fatty acid composition of milk fat reflected changes in the relative contributions of body fat mobilization and de novo synthesis of milk fat components in response to changes in energy balance. Initiation of bST treatment caused some transient changes in milk fatty acid composition that were related to energy balance. These changes were small compared with the normal changes because of stage of lactation in all cows. Phospholipid and cholesterol content of milk also changed with stage of lactation but were not influenced by bST treatment. Melting properties of milk fat were influenced greatly by stage of lactation. Bovine somatotropin did not cause any changes in composition or physical properties of milk fat that were outside the range of normal variation.
对9头荷斯坦奶牛每两周注射一次缓释型N-甲硫氨酰bST，另外9头奶牛注射赋形剂。肌肉注射从产后60±3天开始，每14天注射一次，持续整个泌乳期。注射bST可提高牛奶、总脂肪以及所测的所有乳脂肪成分的产量。bST处理对乳脂肪的平均脂肪酸组成没有影响。泌乳阶段对bST处理组和对照组奶牛乳脂肪中各脂肪酸的产量和百分比有很大影响。泌乳阶段对乳脂肪脂肪酸组成的影响反映了体脂动员和乳脂肪成分从头合成对能量平衡变化的相对贡献的变化。开始注射bST会导致乳脂肪酸组成出现一些与能量平衡相关的短暂变化。与所有奶牛因泌乳阶段引起的正常变化相比，这些变化较小。牛奶中的磷脂和胆固醇含量也随泌乳阶段而变化，但不受bST处理的影响。乳脂肪的熔化特性受泌乳阶段的影响很大。牛生长激素不会导致乳脂肪的组成或物理性质发生超出正常变化范围的改变。
