School of Veterinary Medicine, University of California, Davis, California 95616, USA.
Reproduction. 2009 May;137(5):813-23. doi: 10.1530/REP-08-0242. Epub 2009 Feb 9.
Length of dominance of the ovulatory follicle and exposure to oestradiol (OE(2)) during proestrus can affect fertility. Lactating cows had their oestrous cycle pre-synchronized and were subjected to one of the four synchronization treatments. Cows in the oestrus detection (OD) treatment received GnRH on day 6 of the oestrous cycle, PGF(2alpha) 7 days later, and were inseminated at detected oestrus. The remaining cows were subjected to the Ovsynch (OVS) protocol (day 0 GnRH, day 7 PGF(2alpha), day 9 GnRH, and timed artificial insemination (AI) 12 h later) starting on day 3 (OVS3) or day 6 (OVS6 and OVS6E) of the oestrous cycle. Cows in the OVS6E treatment received an injection of 0.5 mg oestradiol cypionate 36 h before AI. Ovaries were examined by ultrasonography and blood was sampled for progesterone and OE(2) concentrations. Uteri were flushed 6 days after AI and recovered embryos-oocytes evaluated. Diameter of the ovulatory follicle at AI differed (P<0.01) among treatments, and it was the largest for OVS3 cows, which also had extended (P<0.01) length of follicular dominance. During proestrus, OD and OVS6E cows had increased (P<0.01) OE(2) concentrations. Fertilization was not altered by treatments, and maximum fertilization was achieved when the number of accessory spermatozoa was >7. Proportions of viable embryos in relation to embryos and embryos-oocytes recovered were smaller for OVS3 cows (P<0.01) than the other treatments, and embryos from OVS3 cows also had fewer (P<0.01) blastomeres and tended (P=0.09) to have a lower proportion of live blastomeres. Extending the period of follicle dominance did not alter fertilization but reduced (P<0.001) embryo quality. Embryo quality was compromised even when the dominance of the ovulatory follicle was extended by only 1.5 days.
排卵卵泡的优势期长度以及发情前期暴露于雌二醇（OE(2)）的情况会影响生育能力。对泌乳母牛的发情周期进行预同步处理，并使其接受四种同步处理之一。发情检测（OD）处理组的母牛在发情周期的第6天接受促性腺激素释放激素（GnRH），7天后接受前列腺素F2α（PGF(2α)），并在检测到发情时进行授精。其余母牛从发情周期的第3天（OVS3）或第6天（OVS6和OVS6E）开始接受Ovsynch方案（第0天注射GnRH，第7天注射PGF(2α)，第9天注射GnRH，12小时后进行定时人工授精（AI））。OVS6E处理组的母牛在人工授精前36小时注射0.5毫克环丙孕酮。通过超声检查卵巢，并采集血液检测孕酮和OE(2)浓度。人工授精6天后冲洗子宫，对回收的胚胎-卵母细胞进行评估。人工授精时排卵卵泡的直径在各处理组之间存在差异（P<0.01），其中OVS3组母牛的卵泡直径最大，其卵泡优势期也延长了（P<0.01）。在发情前期，OD组和OVS6E组母牛的OE(2)浓度升高（P<0.01）。各处理对受精没有影响，当副精子数量>7时可实现最大受精率。OVS3组母牛回收的胚胎和胚胎-卵母细胞中活胚胎的比例（P<0.01）低于其他处理组，且OVS3组母牛的胚胎卵裂球数量也较少（P<0.01），活卵裂球的比例有降低趋势（P=0.09）。延长卵泡优势期不会改变受精情况，但会降低（P<0.001）胚胎质量。即使排卵卵泡的优势期仅延长1.5天，胚胎质量也会受到影响。
