Schmitt E J, Diaz T, Drost M, Thatcher W W
Department of Dairy, University of Florida, Gainesville 32611-0920, USA.
J Anim Sci. 1996 May;74(5):1084-91. doi: 10.2527/1996.7451084x.
Three experiments were conducted to evaluate a synchronization protocol with AI at a predetermined time. In Exp. 1, 169 dairy heifers were assigned randomly to two groups: 1) timed AI (TAI), consisting of GnRH agonist injection (d 0, 1700), PGF2 alpha injection (d 7, 1700), GnRH agonist injection (d 8, 1700), and AI (d 9, 0800); and 2) AI at estrus (AIE), consisting of GnRH agonist injection (d 0, 1700), PGF2 alpha injection (d 7, 1700), and AI at detected estrus. Pregnancy rate was 25.8% for TAI (n = 89) compared with 48.7% for AIE (n = 80; P < .001). Experiment 2 was comparable to Exp. 1, but the second GnRH agonist injection in TAI was given 48 h after injection of PGF2 alpha. Heifers in TAI (n = 187) were inseminated at detected estrus if estrus occurred within 39 h after administration of PGF2 alpha (n = 47). Pregnancy rates were 45.5% for TAI and 48.0% for AIE (n = 177). Conception rate was reduced for TAI (45.5 [85/187] < 61.2% [85/139]; P < .005). In Exp. 3, the second injection of GnRH agonist, given at 48 h after injection of PGF2 alpha, was replaced with hCG (3,000 IU, i.m.). No differences in pregnancy rate were detected for TAI (52.9% [54/102]) vs AIE (56.1% [55/98]). Conception rate was reduced for TAI (52.9 [54/102] < 72.3% [55/76]; P < .005). Delaying the second GnRH agonist injection by 24 h improved pregnancy rate, but replacing the second injection of GnRH agonist with an injection of hCG did not prevent a reduction in conception rate.
进行了三项实验以评估在预定时间采用人工智能的同步方案。在实验1中，169头奶牛小母牛被随机分为两组：1）定时人工授精（TAI）组，包括注射促性腺激素释放激素（GnRH）激动剂（第0天，17:00）、注射前列腺素F2α（PGF2α）（第7天，17:00）、注射GnRH激动剂（第8天，17:00）以及人工授精（第9天，08:00）；2）发情期人工授精（AIE）组，包括注射GnRH激动剂（第0天，17:00）、注射PGF2α（第7天，17:00）以及在检测到发情时进行人工授精。TAI组（n = 89）的妊娠率为25.8%，而AIE组（n = 80；P <.001）的妊娠率为48.7%。实验2与实验1类似，但TAI组中第二次注射GnRH激动剂是在注射PGF2α后48小时进行。如果在注射PGF2α后39小时内出现发情，TAI组（n = 187）的小母牛在检测到发情时进行授精（n = 47）。TAI组的妊娠率为45.5%，AIE组（n = 177）的妊娠率为48.0%。TAI组的受孕率降低（45.5 [85/187] < 61.2% [85/139]；P <.005）。在实验3中，在注射PGF2α后48小时注射的第二次GnRH激动剂被人绒毛膜促性腺激素（hCG，3000国际单位，肌肉注射）取代。TAI组（52.9% [54/102]）与AIE组（56.1% [55/98]）的妊娠率未检测到差异。TAI组的受孕率降低（52.9 [54/102] < 72.3% [55/76]；P <.005）。将第二次GnRH激动剂注射延迟24小时可提高妊娠率，但用hCG注射取代第二次GnRH激动剂注射并不能防止受孕率降低。
