Schmitt E J, Drost M, Diaz T, Roomes C, Thatcher W W
Department of Dairy and Poultry Sciences, University of Florida, Gainesville 32611-0920, USA.
J Anim Sci. 1996 Jan;74(1):154-61. doi: 10.2527/1996.741154x.
Two experiments were conducted to determine whether a GnRH agonist eliminated a potentially persistent first-wave dominant follicle (PDF) and recruited a new dominant follicle with improved fertility upon ovulation. In Exp. 1, five nonlactating Holstein cows were treated on d 7 (d 0 = estrus) with a norgestomet implant and PGF2 alpha (25 mg); a GnRH agonist was injected on d 9. On d 16, the norgestomet implant was removed and PGF2 alpha was injected. The corpus luteum (CL) regressed (5/5 cows), and plasma progesterone (P4) decreased (P < .01) from d 7 (P4 = 10.4 +/- .3) to 9 (P4 = 1.0 +/- .3 ng/mL). The GnRH agonist induced ovulation of the first-wave dominant follicle. New dominant follicles emerged by d 12 +/- 1. In all cows, removal of norgestomet implants and injection of PGF2 alpha on d 16 caused regression (P < .01) of the CL induced by the GnRH agonist. The GnRH agonist-recruited dominant follicles were highly estrogenic on d 17 (estradiol = 19.6 +/- .8 pg/mL) and ovulated on d 19.8 +/- .2 (5/5). In Exp. 2, 147 heifers at a synchronized estrus were assigned disproportionally but randomly to two treatments (GnRHa, n = 94; PDF, n = 53). On d 7, a used controlled internal drug releasing (CIDR-B) device was inserted into the vagina and PGF2 alpha was injected. On d 9, heifers in GnRHa were injected with GnRH agonist. The CIDR-B devices were removed and PGF2 alpha was injected into all heifers on d 16. Within 4 d after removal of CIDR-B devices, 96.8 and 94.3% of heifers in GnRHa and PDF were detected in estrus and inseminated. Pregnancy rates were GnRHa = 60.6% > PDF = 43.4% (P < .05). In summary, fertility after ovulation of a persistent first-wave dominant follicle is reduced, whereas induction of a new dominant follicle following injection of a GnRH agonist results in greater fertility.
进行了两项实验，以确定促性腺激素释放激素（GnRH）激动剂是否能消除潜在持续存在的第一波优势卵泡（PDF），并在排卵时募集一个新的优势卵泡以提高生育力。在实验1中，5头非泌乳荷斯坦奶牛在第7天（第0天=发情期）接受诺孕美特植入剂和前列腺素F2α（25毫克）治疗；在第9天注射GnRH激动剂。在第16天，取出诺孕美特植入剂并注射前列腺素F2α。黄体（CL）退化（5/5头奶牛），血浆孕酮（P4）从第7天（P4 = 10.4±0.3）降至第9天（P4 = 1.0±0.3纳克/毫升）（P <.01）。GnRH激动剂诱导第一波优势卵泡排卵。到第12±1天出现了新的优势卵泡。在所有奶牛中，第16天取出诺孕美特植入剂并注射前列腺素F2α导致GnRH激动剂诱导的黄体退化（P <.01）。GnRH激动剂募集的优势卵泡在第17天雌激素水平很高（雌二醇 = 19.6±0.8皮克/毫升），并在第19.8±0.2天排卵（5/5）。在实验2中，147头同步发情的小母牛被不成比例但随机地分配到两种处理组（GnRHa，n = 94；PDF，n = 53）。在第7天，将用过的控制内部药物释放（CIDR - B）装置插入阴道并注射前列腺素F2α。在第9天，给GnRHa组的小母牛注射GnRH激动剂。在第16天，取出CIDR - B装置并给所有小母牛注射前列腺素F2α。在取出CIDR - B装置后的4天内，GnRHa组和PDF组分别有96.8%和94.3%的小母牛检测到发情并进行了授精。妊娠率为GnRHa = 60.6%>PDF = 43.4%（P <.05）。总之，持续存在的第一波优势卵泡排卵后的生育力降低，而注射GnRH激动剂后诱导新的优势卵泡可提高生育力。
