Esteban E, Kass P H, Weaver L D, Rowe J D, Holmberg C A, Franti C E, Troutt H F
School of Veterinary Medicine, University of California, Davis 95616.
J Dairy Sci. 1994 Feb;77(2):468-81. doi: 10.3168/jds.S0022-0302(94)76975-7.
Reproductive performance in cows exposed for two lactations to recombinant bST was measured using unconditional logistic regression. Intramuscular administration of 17.2, 51.6, and 86 mg of recombinant bST/d per cow started at d 70 postpartum and ended at dry-off or 305 d postpartum. Performance was measured as the cumulative incidence of cows becoming pregnant by 305 d post-partum. Within each parity group, cows treated with bST had higher total milk yield. During the first study lactation, the log odds of a cow becoming pregnant decreased linearly as dose increased, following adjustment for serum cholesterol, blood urea N, average daily milk yield, peak milk yield, net energy balance, and body condition score. However, differences in pregnancy incidence between treated and untreated cows were statistically significant only at the higher dose categories, the 51.6 and 86.0 mg of recombinant bST per cow. During the second study lactation, pregnancy rates were similar to those in the first lactation; rates reduced as recombinant bST dose increased. The singular exception was for cows exposed to recombinant bST during the previous lactation but not during the second. In the latter group, previously treated cows had higher pregnancy incidence than did the controls.
采用无条件逻辑回归分析，对连续两个泌乳期接受重组牛生长激素（bST）处理的奶牛的繁殖性能进行了测定。每头奶牛产后70天开始，每天肌肉注射17.2、51.6和86毫克重组bST，直至干奶期或产后305天结束。繁殖性能以产后305天内怀孕奶牛的累积发病率来衡量。在每个胎次组中，接受bST处理的奶牛总产奶量更高。在第一个泌乳期研究中，在对血清胆固醇、血尿素氮、日均产奶量、产奶高峰量、净能量平衡和体况评分进行校正后，奶牛怀孕的对数几率随剂量增加呈线性下降。然而，仅在较高剂量组，即每头奶牛51.6毫克和86.0毫克重组bST时，处理组和未处理组奶牛的怀孕率差异才具有统计学意义。在第二个泌乳期研究中，怀孕率与第一个泌乳期相似；怀孕率随重组bST剂量增加而降低。唯一的例外是前一个泌乳期接受重组bST处理但第二个泌乳期未接受处理的奶牛。在后一组中，先前接受处理的奶牛的怀孕率高于对照组。
