Morgan W F, Lean I J
Department of Animal Science, University of Sydney, Camden, New South Wales.
Aust Vet J. 1993 Jun;70(6):205-9. doi: 10.1111/j.1751-0813.1993.tb03304.x.
Data from 40 trials described in 27 published papers were analysed by meta-analysis (pooling of data from numerous trials into a single analysis) to evaluate the effects of injecting gonadotrophin-releasing hormone (GnRH) in cattle at the time of insemination on the risk of pregnancy. A total of 19,019 cows were involved in these studies. Analyses were stratified by trial and by the effects of dose of GnRH, type of GnRH and insemination number (first, second or third and greater). Mantel-Haenszel analysis revealed that use of GnRH at insemination significantly increased the overall risk of pregnancy by 12.5% in treated cows (P < 0.05). However, increases in risk of pregnancy were greatest (22.5%) when repeat breeders were tested. Results for use of GnRH or analogue at first service were similar, with increased risks of pregnancy in treated cows of 5.2 and 8.0%, respectively. The risk of pregnancy tended to be higher (11.1%) when the dose of GnRH was > or = 250 micrograms and when used at second insemination (9.9%). The analyses demonstrated that while treatment at insemination with GnRH and GnRH analogues increased conception rates in dairy cattle, some variation in study results was attributable to the number of inseminations after calving at which GnRH is administered. Further efforts should be made to determine characteristics of populations of cows that have good fertility responses to GnRH and to determine the mode of action of GnRH in increasing fertility.(ABSTRACT TRUNCATED AT 250 WORDS)
通过荟萃分析（将众多试验的数据汇总到单一分析中）对27篇已发表论文中描述的40项试验数据进行分析，以评估在授精时给牛注射促性腺激素释放激素（GnRH）对怀孕风险的影响。这些研究共涉及19019头奶牛。分析按试验以及GnRH剂量、GnRH类型和授精次数（首次、第二次或第三次及更多次）的影响进行分层。Mantel-Haenszel分析显示，授精时使用GnRH显著增加了经处理奶牛的总体怀孕风险12.5%（P<0.05）。然而，在重复配种母牛中进行测试时，怀孕风险增加最大（22.5%）。首次输精时使用GnRH或其类似物的结果相似，经处理奶牛的怀孕风险分别增加了5.2%和8.0%。当GnRH剂量≥250微克以及在第二次输精时使用时，怀孕风险往往更高（分别为11.1%和9.9%）。分析表明，虽然授精时用GnRH和GnRH类似物处理可提高奶牛的受孕率，但研究结果的一些差异归因于产犊后GnRH给药的输精次数。应进一步努力确定对GnRH有良好繁殖力反应的奶牛群体特征，并确定GnRH提高繁殖力的作用方式。（摘要截短于250词）
