University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
Theriogenology. 2013 Mar 15;79(5):859-66. doi: 10.1016/j.theriogenology.2013.01.003.
The objective was to determine the effect of plasma progesterone concentration and the duration of proestrus during growth of the ovulatory follicle on fertility in beef cattle. Heifers (N = 61) and postpartum cows (N = 79) were assigned randomly to four groups in a two-by-two design involving luteal-phase versus subluteal-phase plasma progesterone concentrations and normal versus short proestrus. To synchronize follicular wave emergence, estradiol-17β was given im during the midluteal phase (Day 0) and concurrently, a once-used controlled intravaginal progesterone-releasing device was placed intravaginally. In the subluteal-phase progesterone groups, a luteolytic dose of PGF(2α) was given on Day 0 and again 12 hours later. In the luteal-phase progesterone groups, PGF(2α) was not given (so as to retain a functional CL). The controlled intravaginal progesterone-releasing device was removed and PGF(2α) was given on Days 7 or 8 in the normal- and short-proestrus groups, respectively. Cattle were given lutropin im 12 or 36 hours later in the short- and normal-proestrus groups, respectively, with AI at 12 hours after lutropin treatment. Transrectal ultrasonography was used to monitor ovarian response during treatments and to diagnose pregnancy 60 days after AI. Cattle (heifers and cows combined) in the subluteal-phase progesterone groups and normal proestrus groups had a larger follicle at the time of AI, and a larger CL that secreted more progesterone 9 days after AI than cattle with luteal-phase progesterone concentrations or those with short proestrus (P < 0.03). There was a higher incidence of ovulation (P < 0.01) the day after AI in heifers (55/61; 90%) than in cows (44/79; 56%). Pregnancy rates ranged from 11% to 54%, and were higher in cattle (heifers and cows combined) in the subluteal-phase progesterone groups and normal proestrus groups than in the luteal-phase progesterone or short proestrus groups, respectively, (P < 0.02). In conclusion, a short proestrous interval reduced pregnancy rate after fixed-time AI in beef cattle. A low progesterone environment during growth of the ovulatory follicle increased the preovulatory follicle size and subsequent CL size and function, and compensated for the effect of a short proestrus on pregnancy rates.
本研究旨在确定促黄体素（LH）峰出现前血浆孕酮浓度和发情持续时间对牛超数排卵的影响。试验选择了 61 头小母牛和 79 头产后奶牛，随机分为 4 组，每组 17 头。这 4 组分别为黄体期和 LH 峰期血浆孕酮浓度、正常发情和发情持续时间缩短。为了同步卵泡波的出现，在发情周期的中期（第 0 天）肌肉注射雌二醇 17β，同时阴道内放置一次性使用的阴道内孕酮释放装置。在 LH 峰期孕酮组，在第 0 天和 12 小时后给予溶黄体素 PG F2α。在黄体期孕酮组，不给 PG F2α（以保留功能性黄体）。在正常发情和发情持续时间缩短组，分别在第 7 天和第 8 天取出阴道内孕酮释放装置并给予 PG F2α。在发情持续时间缩短和正常发情组，分别在 12 小时和 36 小时后肌肉注射促黄体素，在处理后 12 小时进行人工授精。直肠超声监测治疗期间的卵巢反应，并在人工授精后 60 天诊断妊娠。LH 峰期孕酮组和正常发情组的小母牛和产后奶牛在人工授精时的卵泡更大，在人工授精后 9 天的黄体更大，分泌更多的孕酮（P<0.03）。LH 峰期孕酮组和正常发情组的小母牛在人工授精后第二天排卵的比例更高（P<0.01；55/61；90%），而产后奶牛的排卵比例较低（44/79；56%）。妊娠率在 11%至 54%之间，LH 峰期孕酮组和正常发情组的妊娠率均高于黄体期孕酮组和发情持续时间缩短组（P<0.02）。综上所述，发情持续时间缩短会降低牛定时人工授精的妊娠率。在卵泡生长过程中孕酮浓度低会增加促排卵前卵泡的大小和随后的黄体大小和功能，从而补偿发情持续时间缩短对妊娠率的影响。
