Busch D C, Schafer D J, Wilson D J, Mallory D A, Leitman N R, Haden J K, Ellersieck M R, Smith M F, Patterson D J
Division of Animal Science, S132 ASRC, University of Missouri, Columbia 65211, USA.
J Anim Sci. 2008 Jul;86(7):1519-25. doi: 10.2527/jas.2008-0925. Epub 2008 Mar 14.
This experiment was designed to compare pregnancy rates in postpartum beef cows resulting from fixed-time AI (FTAI) at 54 or 66 h after administration of the CO-Synch + controlled internal drug-release (CIDR) protocol. Cows (n = 851) at 2 locations over 2 yr (yr 1, n = 218 and 206; and yr 2, n = 199 and 228 at the 2 locations, respectively) were stratified by age, BCS, and days postpartum to 1 of 2 FTAI intervals. Cows were administered GnRH (100 mug, i.m.) and were equipped with a CIDR insert (1.38 g of progesterone) on d 0. Controlled internal drug-release inserts were removed 7 d later at the time PGF(2alpha) (25 mg, i.m.) was administered (d 7). Continuous estrus detection was performed at location 2 by using the HeatWatch Estrus Detection System; the transmitters were fitted at the time of PGF(2alpha) and removed at the time of AI. Artificial insemination was performed at predetermined fixed times [54 h (FTAI 54; n = 424) or 66 h (FTAI 66; n = 427) after PGF(2alpha)] and all cows were administered GnRH (100 mug, i.m.) at AI. Two blood samples were collected on d -10 or -8 and immediately before treatment initiation to determine the pretreatment estrous cyclicity status of cows [progesterone >/=0.5 ng/mL (FTAI 54, 288/424 = 68%; FTAI 66, 312/427 = 73%; P = 0.07)]. Pregnancy rates were greater (P < 0.01) among cows that exhibited estrus than among those that did not (123/163 = 76% and 150/270 = 56%, respectively). There were no treatment x location interactions within year (P > 0.10) for age, days postpartum, or BCS; thus, the results were pooled for the respective treatments. Pregnancy rates were greater for FTAI 66 than FTAI 54 (P = 0.05; 286/426 = 67% vs. 257/424 = 61%, respectively). Pregnancy rates resulting from FTAI did not differ between year (P = 0.09), farm (P = 0.80), AI sire (P = 0.11), or technician (P = 0.64). There was no difference between pregnancy rates resulting from FTAI based on pretreatment cyclicity status (P = 0.30), and there was no difference between treatments in final pregnancy rates (P = 0.77). In summary, pregnancy rates resulting from FTAI following CO-Synch + CIDR at 66 h were greater than those resulting from FTAI at 54 h.
本试验旨在比较采用CO-Synch+控制内部药物释放（CIDR）方案后54小时或66小时定时人工授精（FTAI）的产后肉牛妊娠率。在两年内，对两个地点的851头母牛（第1年，两个地点分别为218头和206头；第2年，两个地点分别为199头和228头）按年龄、体况评分（BCS）和产后天数分层，分为两个FTAI间隔之一。母牛在第0天肌肉注射促性腺激素释放激素（GnRH，100μg）并植入CIDR栓（含1.38g孕酮）。7天后，即第7天肌肉注射前列腺素F2α（PGF2α，25mg）时取出CIDR栓。在地点2使用HeatWatch发情检测系统进行连续发情检测；发射器在注射PGF2α时安装，在人工授精时取下。在预定的固定时间（注射PGF2α后54小时（FTAI 54；n=424）或66小时（FTAI 66；n=427））进行人工授精，所有母牛在人工授精时肌肉注射GnRH（100μg）。在第-10天或-8天以及治疗开始前立即采集两份血样，以确定母牛的预处理发情周期状态[孕酮≥0.5ng/mL（FTAI 54，288/424=68%；FTAI 66，312/427=73%；P=0.07）]。表现出发情的母牛妊娠率高于未发情的母牛（分别为123/163=76%和150/270=56%，P<0.01）。年龄、产后天数或BCS在各年份内不存在处理×地点交互作用（P>0.10）；因此，将各处理的结果合并。FTAI 66的妊娠率高于FTAI 54（P=0.05；分别为286/426=67%和257/424=61%）。FTAI的妊娠率在年份（P=0.09）、农场（P=0.80）、人工授精公牛（P=0.11）或技术人员（P=0.64）之间无差异。基于预处理周期状态的FTAI妊娠率之间无差异（P=0.30），最终妊娠率在各处理之间也无差异（P=0.77）。总之，CO-Synch+CIDR方案后66小时FTAI的妊娠率高于54小时FTAI的妊娠率。
