Fricke P M, Guenther J N, Wiltbank M C
Department of Dairy Science, University of Wisconsin-Madison 53706, USA.
Theriogenology. 1998 Dec;50(8):1275-84. doi: 10.1016/s0093-691x(98)00226-x.
To determine the efficacy of reducing the dosage of GnRH used in a protocol for synchronization of ovulation and timed AI, primiparous and multiparous lactating Holstein cows (n = 237) were randomly assigned to 1 of 2 treatment groups. Ovulation was synchronized for cows in the first group using intramuscular injections of GnRH and PGF2 alpha as follows: Day 0, 100 micrograms GnRH; Day 7, 25 mg PGF2 alpha; Day 9, 100 micrograms GnRH. Ovulation was synchronized in the second group of cows using the same injection schedule and dosage of PGF2 alpha but only 50 micrograms GnRH per injection. All cows underwent a timed AI at 12 to 18 h after the second GnRH injection. The proportion of cows ovulating in response to the second GnRH injection (synchronization rate) and pregnancy status at 28 and 56 d post AI were determined using transrectal ultrasonography. The synchronization rate, double-ovulation rate, conception rate at 28 and 56 d post AI, and pregnancy loss from 28 to 56 d post AI did not differ statistically between treatment groups. For all cows, synchronization rate was 84.0%, and double-ovulation rate was 14.1%. Conception rates calculated using all cows receiving synchronization of ovulation were 41.1% at 28 d and 34.4% at 56 d post AI. Conception rates calculated for only synchronized cows were 47.6% at 28 d and 40.1% at 56 d post AI. For all cows, pregnancy loss from 28 to 56 d post AI was 13.5%, with an attrition rate of 0.5% per day. Estimated savings in hormone costs using 50 rather than 100 micrograms GnRH per injection for synchronizing ovulation were $6.40 per cow and $20.27 per pregnancy. Thus, decreasing the dosage of GnRH used for synchronization of ovulation and timed AI in lactating dairy cows reduces synchronization costs per cow and per pregnancy without compromising the efficacy of the synchronization protocol.
为了确定在排卵同步化和定时人工授精方案中减少促性腺激素释放激素（GnRH）用量的效果，将初产和经产泌乳荷斯坦奶牛（n = 237）随机分为2个处理组之一。第一组奶牛的排卵同步化采用肌肉注射GnRH和前列腺素F2α（PGF2α），具体如下：第0天，100微克GnRH；第7天，25毫克PGF2α；第9天，100微克GnRH。第二组奶牛的排卵同步化采用相同的注射方案和PGF2α剂量，但每次注射仅50微克GnRH。所有奶牛在第二次GnRH注射后12至18小时进行定时人工授精。使用经直肠超声检查确定对第二次GnRH注射有反应而排卵的奶牛比例（同步化率）以及人工授精后28天和56天的妊娠状态。处理组之间的同步化率、双排卵率、人工授精后28天和56天的受孕率以及人工授精后28天至56天的妊娠损失在统计学上没有差异。对于所有奶牛，同步化率为84.0%，双排卵率为14.1%。使用所有接受排卵同步化的奶牛计算的受孕率在人工授精后28天为41.1%，在人工授精后56天为34.4%。仅对同步化奶牛计算的受孕率在人工授精后28天为47.6%，在人工授精后56天为40.1%。对于所有奶牛，人工授精后28天至56天的妊娠损失为13.5%，每天的损耗率为0.5%。估计在排卵同步化中每次注射使用50微克而非100微克GnRH，每头奶牛的激素成本节省6.40美元，每例妊娠节省20.27美元。因此，在泌乳奶牛中降低用于排卵同步化和定时人工授精的GnRH用量，可降低每头奶牛和每例妊娠的同步化成本，而不影响同步化方案的效果。
