Department of Animal Sciences, University of Florida, Gainesville 32611, USA.
J Dairy Sci. 2010 Apr;93(4):1500-10. doi: 10.3168/jds.2009-2489.
The objectives of this study were to evaluate the effect of administering 500 mg of recombinant bovine somatotropin (bST) every 10 d on ovulatory responses, estrous behavior, and fertility of lactating Holstein cows. Lactating dairy cows were assigned to 1 of 2 treatments: a control with no administration of bST (73 primiparous and 120 multiparous cows) or 6 consecutive administrations of 500 mg of bST (83 primiparous and 123 multiparous cows) given subcutaneously at 10-d intervals starting 61+/-3 d postpartum (study d 0), concurrent with the initiation of the timed artificial insemination (AI). Blood samples were collected thrice weekly from 61+/-3 to 124+/-3 d in milk (DIM), and plasma samples were analyzed for concentrations of estradiol, glucose, insulin, insulin-like growth factor 1, and progesterone. The estrous cycle of cows was presynchronized with 2 injections of PGF(2alpha) at 37+/-3 and 51+/-3 DIM, and the Ovsynch timed AI protocol was initiated at 61+/-3 DIM. Ovaries were scanned to determine ovulatory responses during the Ovsynch protocol. Pregnancy was diagnosed at 33 and 66 d after AI. Body condition was scored on study d 0, 10, 42, and 76. Sixty-four cows were fitted with a pressure mounting sensor with radiotelemetric transmitters to monitor estrous behavior. Treatment of lactating dairy cows with 500 mg of bST at 10-d intervals increased yields of milk and milk components in the first 2 mo after treatment. Body condition of bST-treated cows remained unaltered, whereas control cows gained BCS. Treatment with bST increased concentrations of insulin-like growth factor 1 chronically, but concentrations of insulin and glucose increased only transiently in the first 7 d after the first injection of bST. Concentrations of progesterone during and after the Ovsynch protocol remained unaltered after treatment with bST; likewise, ovulatory responses during the Ovsynch protocol were mostly unaltered by treatment. Concentration of estradiol tended to be greater for bST cows than for control cows immediately before induction of ovulation in the Ovsynch protocol. Similarly, the mean and the peak concentrations of estradiol were greater for bST cows than for control cows when monitored during spontaneous estrus. Nevertheless, duration of estrus and the median number of standing events were less for bST cows than for control cows. Pregnancies per AI after the first and second postpartum inseminations were not affected by bST treatment. Treatment of lactating dairy cows with 500 mg of bST every 10 d improved lactation performance, but it did not affect pregnancies per AI and it reduced expression of estrus.
本研究的目的是评估每隔 10 天给予 500 毫克重组牛生长激素（bST）对泌乳荷斯坦奶牛排卵反应、发情行为和生育力的影响。泌乳奶牛被分配到以下 2 种处理之一：不给予 bST 的对照组（73 头初产和 120 头经产奶牛）或每隔 10 天连续给予 6 次 500 毫克 bST（83 头初产和 123 头经产奶牛），皮下给药，从产后第 61+/-3 天（研究 d0）开始，同时启动定时人工授精（AI）。从产后第 61+/-3 天至第 124+/-3 天，每周采集 3 次血样，分析血浆中雌二醇、葡萄糖、胰岛素、胰岛素样生长因子 1 和孕酮的浓度。通过在产后第 37+/-3 天和第 51+/-3 天给予 2 次 PGF(2alpha)，使奶牛的发情周期同步，在产后第 61+/-3 天开始进行 Ovsynch 定时 AI 方案。在 Ovsynch 方案期间，通过扫描卵巢来确定排卵反应。在 AI 后 33 和 66 天进行妊娠诊断。在研究 d0、10、42 和 76 时对体况进行评分。对 64 头奶牛安装带有遥测发射器的压力安装传感器以监测发情行为。每隔 10 天给泌乳奶牛注射 500 毫克 bST，可提高治疗后头 2 个月的牛奶和牛奶成分产量。bST 处理奶牛的体况保持不变，而对照组奶牛的体况增加。bST 处理可长期增加胰岛素样生长因子 1 的浓度，但在第一次注射 bST 后的前 7 天，胰岛素和葡萄糖的浓度仅短暂增加。bST 处理后，Ovsynch 方案期间和之后的孕酮浓度保持不变；同样，Ovsynch 方案期间的排卵反应也基本不受 bST 处理的影响。与对照组奶牛相比，bST 奶牛在 Ovsynch 方案中诱导排卵前雌二醇的浓度往往更高。同样，在自然发情期间监测时，bST 奶牛的雌二醇平均和峰值浓度也高于对照组奶牛。然而，bST 奶牛的发情持续时间和站立事件中位数比对照组奶牛少。第一次和第二次产后授精后的每头 AI 妊娠数不受 bST 处理的影响。每隔 10 天给泌乳奶牛注射 500 毫克 bST 可改善泌乳性能，但对每头 AI 妊娠数没有影响，且降低了发情表达。
