Department of Animal Sciences, Colorado State University, Fort Collins 80523, USA.
J Anim Sci. 2013 Apr;91(4):1866-73. doi: 10.2527/jas.2012-5497. Epub 2013 Jan 23.
Many estrus synchronization protocols aim to induce a new follicular wave to improve response and enhance pregnancy rate. Our objectives were to determine the effectiveness of GnRH analog administered d 0 and 9 during an extended controlled internal drug release (CIDR) protocol to produce 2 follicular waves, induce cyclicity in anestrus cows, and evaluate the efficacy of a single 50-mg dose of PGF2α to initiate luteal regression on CIDR removal. Lactating beef cows (n = 779) at 3 locations (n = 247, location 1; n = 395, location 2; n = 137, location 3) were randomly assigned to 1 of 3 treatments. Cows in the 14-d 50 PG treatment received a CIDR (1.38 g progesterone) with 100 μg GnRH analog intramuscularly (i.m.) on d 0, 100 μg GnRH analog i.m. on d 9, and CIDR removal concurrent with 50 mg PGF2α i.m. on d 14. Cows in the 14-d 6-h PG treatment were assigned the same protocol as the 14-d 50 PG treatment except that 25 mg PGF2α i.m. was given on d 14 plus 25 mg PGF2α i.m. 6 ± 1 h later. Cows in the control treatment, 5-d CO-Synch + CIDR (5-d CO-Synch), received a CIDR concurrent with 100 μg GnRH analog i.m. on d 9, CIDR removal concurrent with 25 mg PGF2α i.m. on d 14, and 25 mg PGF2α i.m. 6 ± 1 h after first F2α injection. Cows in all treatments received 100 μg GnRH analog i.m. and timed AI (TAI) 72 ± 3 h after CIDR removal. Pregnancy status to TAI was determined by ultrasonography 37 to 40 d after TAI. Averaged over all locations, pregnancy rates to TAI for 14-d 50 PG, 14-d 6-h PG, and 5-d CO-Synch treatments were 58.2%, 46.8%, and 41.9%, respectively. Pregnancy rates to TAI were greater (P < 0.05) in 14-d 50 PG treatment than 14-d 6-h PGF2α and 5-d CO-Synch treatments. Cycling status at 2 locations (n = 243, location 1; n = 391, location 2) was determined from blood collected on d -7 and 0; cows with serum progesterone concentrations >1 ng/mL at either (or both) bleeding date were considered cyclic. Averaged over the 2 locations, there was a tendency (P = 0.06) for a greater number of cyclic animals to become pregnant to TAI in the 14-d 50 PG treatment (64.4%) than 5-d CO-Synch treatment (50.2%). The 14-d CIDR with GnRH analog on d 0 and 9 and a single 50-mg dose of PG i.m. at CIDR removal was a more efficacious protocol to maximize TAI pregnancy rates than the standard 5-d CO-Synch.
许多发情同步方案旨在诱导新的卵泡波，以提高反应和提高妊娠率。我们的目标是确定 GnRH 类似物在延长的控制内部药物释放（CIDR）方案中在第 0 天和第 9 天给药以产生 2 个卵泡波，诱导乏情奶牛的周期性，并评估单次 50mgPGF2α剂量启动CIDR 去除时黄体退化的效果。来自 3 个地点（n = 247，地点 1；n = 395，地点 2；n = 137，地点 3）的泌乳肉牛（n = 779）被随机分配到 3 种处理之一。14d 50PG 治疗组的奶牛在第 0 天接受 CIDR（1.38g 孕酮），并肌肉内注射 100μg GnRH 类似物，第 9 天肌肉内注射 100μg GnRH 类似物，第 14 天肌肉内注射 50mgPGF2α同时去除 CIDR。14d 6-hPG 治疗组的奶牛接受了与 14d 50PG 治疗相同的方案，但在第 14 天肌肉内注射 25mgPGF2α，并在 6 ± 1 小时后再肌肉内注射 25mgPGF2α。对照组，5d CO-Synch+CIDR（5d CO-Synch）在第 9 天肌肉内注射 CIDR 时同时接受 100μg GnRH 类似物，在第 14 天肌肉内注射 CIDR 时同时去除 CIDR，在第一次 F2α 注射后 6 ± 1 小时肌肉内注射 25mgPGF2α。所有治疗组的奶牛在 CIDR 去除后 72 ± 3 小时肌肉内注射 100μg GnRH 类似物并进行定时人工授精（TAI）。TAI 后 37 至 40 天通过超声检查确定妊娠状况至 TAI。在所有地点的平均值中，14d 50PG、14d 6-hPG 和 5d CO-Synch 治疗的 TAI 妊娠率分别为 58.2%、46.8%和 41.9%。14d 50PG 治疗的 TAI 妊娠率高于 14d 6-hPG 和 5d CO-Synch 治疗（P<0.05）。在 2 个地点（n = 243，地点 1；n = 391，地点 2）从-7 天和 0 天采集的血液中确定了循环状态；在任何（或两者）出血日期血清孕酮浓度>1ng/mL 的奶牛被认为是循环的。在 2 个地点的平均值中，14d 50PG 治疗（64.4%）比 5d CO-Synch 治疗（50.2%）更倾向于使更多的循环动物怀孕至 TAI（P = 0.06）。第 0 天和第 9 天用 GnRH 类似物进行的 14d CIDR 和 CIDR 去除时单次 50mgPG 肌肉内注射是一种更有效的方案，可以提高 TAI 妊娠率，优于标准的 5d CO-Synch。
