Galvão K N, Santos J E P, Juchem S O, Cerri R L A, Coscioni A C, Villaseñor M
Veterinary Medicine Teaching and Research Center, University of California-Davis, Tulare 93274, USA.
J Anim Sci. 2004 Dec;82(12):3508-17. doi: 10.2527/2004.82123508x.
The objectives of this study were to determine the effects of incorporating a progesterone intravaginal insert (CIDR) between the day of GnRH and PGF2alpha treatments of a timed AI protocol using estradiol cypionate (ECP) to synchronize ovulation on display of estrus, ovulation rate, pregnancy rate, and late embryonic loss in lactating cows. Holstein cows, 227 from Site 1 and 458 from Site 2, were presynchronized with two injections of PGF2alpha on study d 0 and 14, and subjected to a timed AI protocol (100 mixrog of GnRH on study d 28, 25 mg of PGF2alpha on study d 35, 1 mg of ECP on study d 36, and timed AI on study d 38) with or without a CIDR insert. Blood was collected on study d 14 and 28 for progesterone measurements to determine cyclicity. Ovaries were scanned on d 35, 37, and 42, and pregnancy diagnosed on d 65 and 79, which corresponded to 27 and 41 d after AI. Cows receiving a CIDR had similar rates of detected estrus (77.2 vs. 73.8%), ovulation (85.6 vs. 86.6%), and pregnancy at 27 (35.8 vs. 38.8%) and 41 d (29.3 vs. 32.3%) after AI, and late embryonic loss between 27 and 41 d after AI (18.3 vs. 16.8%) compared with control cows. The CIDR eliminated cows in estrus before the last PGF2alpha injection and decreased (P < 0.001) the proportion of cows bearing a corpus luteum (CL) at the last PGF2alpha injection because of less ovulation in response to the GnRH and greater spontaneous CL regression. Cyclic cows had greater (P = 0.03) pregnancy rates than anovulatory cows at 41 d after AI (33.8 vs. 20.4%) because of decreased (P = 0.06) late embryonic loss (16.0 vs. 30.3%). The ovulatory follicle was larger (P < 0.001) in cows in estrus, and a greater proportion of cows with follicles > or = 15 mm displayed estrus (P < 0.001) and ovulated (P = 0.05) compared with cows with follicles <15 mm. Pregnancy rates were greater (P < 0.001) for cows displaying estrus, which were related to the greater (P < 0.001) ovulation rate and decreased (P = 0.08) late embryonic loss for cows in estrus at AI. Cows that were cyclic and responded to the presynchronization protocol (high progesterone at GnRH and CL at PGF2alpha) had the highest pregnancy rates. Incorporation of a CIDR insert into a presynchronized timed AI protocol using ECP to induce estrus and ovulation did not improve pregnancy rates in lactating dairy cows. Improvements in pregnancy rates in cows treated with ECP to induce ovulation in a timed AI protocol are expected when more cows display estrus, thereby increasing ovulation rate.
本研究的目的是确定在使用环丙孕酮（ECP）同步排卵的定时人工授精（AI）方案中，在促性腺激素释放激素（GnRH）和前列腺素F2α（PGF2α）治疗日之间插入孕酮阴道栓（CIDR）对泌乳奶牛发情表现、排卵率、妊娠率和晚期胚胎损失的影响。来自第1站点的227头荷斯坦奶牛和来自第2站点的458头荷斯坦奶牛，在研究第0天和第14天用两次PGF2α注射进行预同步处理，然后接受定时AI方案（研究第28天注射100微克GnRH，研究第35天注射25毫克PGF2α，研究第36天注射1毫克ECP，研究第38天定时AI），有或没有插入CIDR。在研究第14天和第28天采集血液进行孕酮测量以确定周期性。在第35、37和42天对卵巢进行扫描，并在第65天和第79天诊断妊娠，这分别对应于人工授精后27天和41天。与对照奶牛相比，接受CIDR的奶牛在人工授精后27天（35.8%对38.8%）和41天（29.3%对32.3%）的发情检出率（77.2%对73.8%）、排卵率（85.6%对86.6%）和妊娠率相似，且在人工授精后27至41天的晚期胚胎损失（18.3%对16.8%）也相似。CIDR消除了最后一次PGF2α注射前发情的奶牛，并降低了（P<0.001）最后一次PGF2α注射时黄体（CL）存在的奶牛比例，这是因为对GnRH的排卵反应较少且自发性CL退化较多。在人工授精后41天，周期性奶牛的妊娠率高于无排卵奶牛（33.8%对20.4%）（P = 0.03），因为晚期胚胎损失减少（P = 0.06）（16.0%对30.3%）。发情奶牛的排卵卵泡更大（P<0.001），与卵泡<15毫米的奶牛相比，卵泡≥15毫米的奶牛中发情（P<0.001）和排卵（P = 0.05）的比例更高。发情奶牛的妊娠率更高（P<0.001），这与发情奶牛在人工授精时更高的排卵率（P<0.001）和降低的晚期胚胎损失（P = 0.08）有关。周期性且对预同步方案有反应（GnRH时孕酮高且PGF2α时CL存在）的奶牛妊娠率最高。在使用ECP诱导发情和排卵的预同步定时AI方案中插入CIDR并不能提高泌乳奶牛的妊娠率。当更多奶牛发情从而提高排卵率时，预计在定时AI方案中用ECP治疗诱导排卵的奶牛妊娠率会提高。
