Macmillan K, Loree K, Mapletoft R J, Colazo M G
Livestock Research Section, Alberta Agriculture and Forestry, Edmonton, Alberta, T6H 5T6 Canada.
Central Veterinary Clinic, Ponoka, Alberta, T4J 1J8 Canada.
J Dairy Sci. 2017 May;100(5):4134-4138. doi: 10.3168/jds.2016-12318. Epub 2017 Feb 23.
Pregnancy per AI (P/AI) following the use of 1 of 2 timed AI (TAI) protocols and 2 different intervals between TAI and resynchronization were compared in heifers that were inseminated with either conventional or sex-sorted semen. Holstein heifers (n = 317; 527 inseminations) were submitted to a 5-d Cosynch protocol with (+) or without (-) GnRH at the time of controlled internal drug release (CIDR) insertion on d 0, CIDR removal and a single PGF treatment on d 5, and TAI plus GnRH on d 8 (72 h later). Visual estrus detection (ED) was conducted on d 6 in the afternoon and d 7 in the morning and heifers observed in estrus were artificially inseminated on d 7 in the afternoon. Heifers were alternately assigned conventional or sex-sorted semen. Pregnancy was diagnosed by ultrasound 27 and 42 d after AI, and heifers diagnosed as nonpregnant were resynchronized, up to 3 times, starting on d 27 or 34 to provide an interbreeding interval of 35 or 42 d. Overall, TAI protocol had no effect on P/AI at 27 or 42 d after artificial insemination or on pregnancy loss, but P/AI following the first service tended to be higher in the -GnRH TAI group (66.3 vs. 56.8%). Pregnancy per AI at 27 d (61.9 vs. 55.5%) tended to differ between conventional and sex-sorted semen. Heifers artificially inseminated based on ED tended to have a greater P/AI (67.6 vs. 58.2%) and had decreased pregnancy loss (0.0 vs. 4.1%) than those submitted to TAI. A greater number of heifers in the -GnRH TAI protocol were artificially inseminated on ED than the +GnRH TAI protocol (21.5 vs. 13.7%). No difference in P/AI was observed between the 35- and 42-d interbreeding intervals; however, more heifers in the 42-d group were artificially inseminated based on ED than in the 35-d group (22.7 vs. 7.8%). A 5-d Cosynch+CIDR TAI protocol without the initial GnRH and with a single PGF at CIDR removal is an acceptable alternative to achieve high P/AI when either conventional or sex-sorted semen is used in Holstein heifers. Breeding heifers based on detected estrus increases labor, but has the potential to increase fertility.
在使用常规精液或性别分选精液进行人工授精的小母牛中，比较了采用两种定时人工授精（TAI）方案中的一种以及TAI与再同步化之间的两种不同间隔后的妊娠率（P/AI）。荷斯坦小母牛（n = 317；527次人工授精）接受了为期5天的Cosynch方案，在第0天插入控制内部药物释放（CIDR）时使用（+）或不使用（-）GnRH，在第5天取出CIDR并进行单次PGF处理，在第8天（72小时后）进行TAI加GnRH。在第6天下午和第7天上午进行视觉发情检测（ED），发情的小母牛在第7天下午进行人工授精。小母牛交替分配使用常规精液或性别分选精液。在人工授精后27天和42天通过超声诊断妊娠，被诊断为未怀孕的小母牛从第27天或第34天开始进行再同步化，最多3次，以提供35天或42天的配种间隔。总体而言，TAI方案对人工授精后27天或42天的P/AI或妊娠损失没有影响，但在-GnRH TAI组中首次输精后的P/AI往往更高（66.3%对56.8%）。常规精液和性别分选精液在27天时的P/AI（61.9%对55.5%）存在差异趋势。基于ED进行人工授精的小母牛的P/AI往往更高（67.6%对58.2%），且妊娠损失低于接受TAI的小母牛（0.0%对4.1%）。-GnRH TAI方案中基于ED进行人工授精的小母牛数量多于+GnRH TAI方案（21.5%对13.7%）。在35天和42天的配种间隔之间未观察到P/AI的差异；然而，42天组中基于ED进行人工授精的小母牛比35天组更多（22.7%对7.8%）。在荷斯坦小母牛中使用常规精液或性别分选精液时，一种在去除CIDR时不使用初始GnRH且仅使用一次PGF的5天Cosynch+CIDR TAI方案是实现高P/AI的可接受替代方案。基于检测到的发情对小母牛进行配种会增加劳动力，但有可能提高繁殖力。
