Reyna J, Thomson P C, Evans G, Maxwell W M C
Centre for Advanced Technologies in Animal Genetics and Reproduction (ReproGen), Faculty of Veterinary Science, University of Sydney, NSW, Australia.
Reprod Domest Anim. 2007 Aug;42(4):410-7. doi: 10.1111/j.1439-0531.2006.00800.x.
The effect of gonadotropin releasing hormone (GnRH) treatment on the time of ovulation and the occurrence of follicular dominance during the non-breeding and breeding seasons (experiment 1), and on fertility after artificial insemination (AI) in the non-breeding season (experiment 2), was examined in Merino ewes. Oestrus was synchronized in 40 nulliparous ewes (experiment 1; n = 20, in the non-breeding and breeding seasons) and in 79 multiparous ewes (experiment 2) using intravaginal sponges and pregnant mare serum gonadotropin. Thirty six hours after sponge removal (SR), half the ewes were injected (i.m.) with 40 microg of synthetic GnRH and the remainder used as controls. GnRH improved the synchrony of ovulation compared with the controls in the breeding (SD = 2.8 vs 5.7 days, p = 0.04) but not the non-breeding season (SD = 3.8 vs 4.4 days, p = 0.69), with ewes ovulating from 42 to 54 h (mean 50.4 +/- 4.08 h) and 42-60 h (mean 54.4 +/- 5.47 h) after SR for GnRH and control, respectively. For both treated and control ewes, ovulation occurred earlier in the non-breeding than the breeding season (50.1 vs 54.6 h; p = 0.002). GnRH had no effect on follicular dominance, as assessed by divergence (D: the time the ovulatory follicle exceeded the average size of the other non-ovulating follicles) or on the interval from D to ovulation (IDO). However, follicular dynamics differed between seasons. The mean follicle diameter increased at a faster rate up to 36 h after SR in the non-breeding compared with the breeding season and then rapidly declined, compared with a later peak (42 h after SR) in mean follicular size during the breeding season. IDO was shorter in the non-breeding than in the breeding season (26.7 +/- 4.30 h vs 39.6 +/- 4.53 h; p = 0.05). In experiment 2, ewes (n = 38 GnRH-treated, n = 40 controls) were inseminated in the uterus by laparoscopy 42 h or 48 h after SR with frozen-thawed sperm. The fertility of ewes treated with GnRH (nine of 39, 23%) was not different to the controls (eight of 38, 21%; p = 0.01). In conclusion the application of GnRH improved synchronization of ovulation but did not improve fertility rates after AI.
在美利奴母羊中研究了促性腺激素释放激素（GnRH）处理对非繁殖季节和繁殖季节排卵时间及卵泡优势化发生情况（实验1），以及对非繁殖季节人工授精（AI）后受胎率的影响（实验2）。使用阴道海绵栓和孕马血清促性腺激素对40只未产母羊（实验1；非繁殖季节和繁殖季节各20只）和79只经产母羊（实验2）进行发情同步化处理。取出海绵栓（SR）36小时后，一半母羊肌肉注射40微克合成GnRH，其余作为对照。与对照相比，GnRH在繁殖季节改善了排卵同步性（标准差分别为2.8天和5.7天，p = 0.04），但在非繁殖季节没有（标准差分别为3.8天和4.4天，p = 0.69），GnRH处理组和对照组母羊分别在SR后42至54小时（平均50.4±4.08小时）和42 - 60小时（平均54.4±5.47小时）排卵。对于处理组和对照组母羊，非繁殖季节的排卵均早于繁殖季节（50.1小时对54.6小时；p = 0.002）。GnRH对卵泡优势化无影响，通过差异度（D：排卵卵泡超过其他未排卵卵泡平均大小的时间）或从D到排卵的间隔时间（IDO）评估均无影响。然而，卵泡动态在不同季节有所不同。与繁殖季节相比，非繁殖季节SR后至36小时平均卵泡直径增加速率更快，随后迅速下降，而繁殖季节平均卵泡大小在SR后较晚达到峰值（42小时）。非繁殖季节的IDO短于繁殖季节（26.7±4.30小时对39.6±4.53小时；p = 0.05）。在实验2中，母羊（38只GnRH处理组，40只对照组）在SR后42小时或48小时通过腹腔镜将冻融精子子宫内输精。GnRH处理组母羊的受胎率（39只中的9只，23%）与对照组（38只中的8只，21%）无差异（p = 0.01）。总之，GnRH的应用改善了排卵同步性，但未提高人工授精后的受胎率。
