Hall J B, Kasimanickam R K, Glaze J B, Roberts-Lew M C
Department of Animal and Veterinary Sciences, University of Idaho, Moscow, ID, USA; UI Nancy M. Cummings Research, Extension & Education Center, Carmen, ID, USA.
Department of Veterinary Clinical Science, Washington State University, Pullman, WA, USA.
Theriogenology. 2017 Oct 15;102:154-161. doi: 10.1016/j.theriogenology.2017.07.014. Epub 2017 Jul 18.
The objectives of the current experiment were to determine if delaying insemination by 8 h in a FTAI protocol would alter estrus expression and pregnancy rates in cows inseminated with sex-sorted semen, characterize bull variation in pregnancy rates to sex-sorted semen and examine the impact of repeated years of FTAI to sex-sorted semen on calving distribution. Over three breeding seasons, postpartum cows (n = 839) were estrous synchronized using the 5-day CO-Synch + CIDR system. Cows were given GnRH (100 μg i.m., Factrel) at time of insertion of a controlled internal drug releasing device (CIDR; Eazi-Breed CIDR). Five d later CIDR was removed and PGF (25 mg i.m., Lutalyse) was given at removal and 8 h later. Estrus detection aids were applied at CIDR removal. Cows were inseminated with X-sorted or Y-sorted sex-sorted semen at 72 h (NORM) or 80 h (DELAY) after CIDR removal, and GnRH was administered at AI. At insemination, estrus status was categorized as positive (YES), partial (QUES), unknown (NR) or negative (NO). Bulls were introduced to cows at 14 d and removed at 60 d after FTAI. Pregnancy diagnosis was performed by ultrasound at d 60 after FTAI and via palpation at 60 d after bull removal. There was no difference (P > 0.05) in pregnancy rates to sex-sorted semen or final pregnancy rates between NORM and DELAY cows. Pregnancy to sex-sorted semen averaged 35.2% whereas final pregnancy rates were 90.6%. More cows (P < 0.05) in the DELAY group expressed estrus before FTAI, but this increase did not alter pregnancy rates to sex-sorted semen. Expression of estrus before FTAI increased (P < 0.02) pregnancy rates to sex-sorted semen across treatments with differences being YES > QUES or NR > NO. There was considerable variation in pregnancy rate by bull (P < 0.05) with pregnancy rates ranging from 55.6% to 19.3%. Whole herd calving distribution was altered (P < 0.05) after 3 y of use of sex-sorted semen compared to the previous 3 y when conventional semen was used. We conclude that delaying insemination by 8 h in an FTAI protocol did not improve pregnancy rates to sex-sorted semen despite more cows exhibiting estrus before FTAI. In addition, a high bull to bull variation in pregnancy rates to sex-sorted semen is a limitation in FTAI systems. Further research into FTAI strategies for use with sex-sorted semen is warranted.
本次实验的目的是确定在定时人工授精（FTAI）方案中将授精延迟8小时是否会改变用性别分选精液授精的奶牛的发情表现和妊娠率，描述公牛对性别分选精液的妊娠率差异，并研究连续多年使用FTAI对性别分选精液的产犊分布的影响。在三个繁殖季节中，对产后奶牛（n = 839头）使用5天的CO-Synch + CIDR系统进行发情同步处理。在插入可控内部药物释放装置（CIDR；Eazi-Breed CIDR）时给奶牛注射促性腺激素释放激素（GnRH，100μg肌肉注射，法特雷）。5天后取出CIDR，并在取出时及8小时后注射前列腺素F2α（25mg肌肉注射，氯前列醇）。在取出CIDR时使用发情检测辅助工具。在取出CIDR后72小时（正常组，NORM）或80小时（延迟组，DELAY），用X分选或Y分选的性别分选精液对奶牛进行授精，并在授精时注射GnRH。在授精时，发情状态分为阳性（是，YES）、部分发情（疑问，QUES）、未知（未记录，NR）或阴性（否，NO）。在FTAI后14天放入公牛，60天后将公牛移出。在FTAI后60天通过超声进行妊娠诊断，并在公牛移出后60天通过直肠触诊进行诊断。正常组和延迟组奶牛对性别分选精液的妊娠率或最终妊娠率没有差异（P>0.05）。对性别分选精液的妊娠率平均为35.2%，而最终妊娠率为90.6%。延迟组中更多奶牛（P<0.05）在FTAI前表现出发情，但这种增加并未改变对性别分选精液的妊娠率。FTAI前的发情表现提高了（P<0.02）不同处理对性别分选精液的妊娠率，差异为阳性>部分发情或未记录>阴性。公牛的妊娠率存在相当大的差异（P<0.05），妊娠率范围为55.6%至19.3%。与之前使用常规精液的3年相比，使用性别分选精液3年后全群的产犊分布发生了改变（P<0.05）。我们得出结论，在FTAI方案中将授精延迟8小时并没有提高对性别分选精液的妊娠率，尽管更多奶牛在FTAI前表现出发情。此外，公牛对性别分选精液的妊娠率差异很大是FTAI系统的一个限制。有必要进一步研究与性别分选精液配合使用的FTAI策略。
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