Department of Animal Science, Cornell University, Ithaca 14853.
Department of Animal Science, Cornell University, Ithaca 14853.
J Dairy Sci. 2017 Sep;100(9):7613-7625. doi: 10.3168/jds.2017-12550. Epub 2017 Jun 28.
Our objectives were to evaluate the pattern of re-insemination, ovarian responses, and pregnancy per artificial insemination (P/AI) of cows submitted to different resynchronization of ovulation protocols. The base protocol started at 25 ± 3 d after artificial insemination (AI) and was as follows: GnRH, 7 and 8 d later PGF, GnRH 32 h after second PGF, and fixed timed AI (TAI) 16 to 18 h after GnRH. At 18 ± 3 d after AI, cows were randomly assigned to the G25 (n = 1,100) or NoG25 (n = 1,098) treatments. The protocol for G25 and NoG25 was the same, except that cows in NoG25 did not receive GnRH 25 ± 3 d after AI. At nonpregnancy diagnosis (NPD), 32 ± 3 d after AI, cows from G25 and NoG25 with a corpus luteum (CL) ≥15 mm in diameter and a follicle ≥10 mm completed the protocol (G25 CL = 272, NoG25 CL = 194), whereas cows from both treatments that did not meet these criteria received a modified Ovsynch protocol with P4 supplementation [controlled internal drug release insert plus GnRH, controlled internal drug release insert removal, and PGF 7 and 8 d later, GnRH 32 h after second PGF, and TAI 16 to 18 h after GnRH (G25 NoCL = 53, NoG25 NoCL = 78)]. Serum concentrations of progesterone (P4) were determined and ovarian ultrasonography was performed thrice weekly from 18 ± 3 d after AI until 1 d after TAI (G25 = 46, NoG25 = 44 cows). A greater percentage of NoG25 cows were re-inseminated at detected estrus (NoG25 = 53.5%, G25 = 44.6%), whereas more cows had a CL at NPD in G25 than NoG25 (83.7 and 71.3%). At 32 d after AI, P/AI was similar for G25 and NoG25 for inseminations at detected estrus (38.4 and 42.9%), TAI services for cows with no CL (40.4 and 36.7%), and for all services combined (39.6 and 39.0%). However, P/AI were greater for cows with a CL in G25 than NoG25 (40.6 and 32.8%) that received TAI. More cows ovulated spontaneously or in response to GnRH for the G25 than the NoG25 treatment (70 and 36%) but a similar proportion had an active follicle at NPD (G25 = 91% and NoG25 = 96%). The largest follicle diameter at NPD (G25 = 15.0 ± 0.4 mm, NoG25 = 16.5 ± 0.6 mm) and days since it reached ≥10 mm (G25 = 4.0 ± 0.3 d, NoG25 = 5.8 ± 0.6 d) were greater for the NoG25 than G25 treatment. For cows with a CL at NPD, CL regression after NPD, ovulation after TAI, and ovulatory follicle diameter did not differ. In conclusion, removing the first GnRH of a modified Resynch-25 protocol for cows with a CL at NPD and a modified Ovsynch protocol with P4 supplementation for cows without a CL at NPD resulted in a greater percentage of cows re-inseminated at detected estrus and a similar proportion of cows pregnant in spite of reduced P/AI for cows with a CL at NPD.
我们的目标是评估不同排卵同步方案下的重复配种模式、卵巢反应和人工授精（AI）后妊娠率（P/AI）。基础方案在 AI 后 25 ± 3 d 开始：GnRH，7 天和 8 天后 PGF，第二次 PGF 后 32 h GnRH，以及固定时间 AI（TAI）在 GnRH 后 16 至 18 h。在 AI 后 18 ± 3 d，奶牛随机分配到 G25（n = 1100）或 NoG25（n = 1098）处理组。G25 和 NoG25 的方案相同，只是 NoG25 奶牛在 AI 后 25 ± 3 d 不接受 GnRH。在非妊娠诊断（NPD）时，即 AI 后 32 ± 3 d，直径≥15 mm 的黄体（CL）和直径≥10 mm 的卵泡的 G25 和 NoG25 奶牛完成了方案（G25 CL = 272，NoG25 CL = 194），而不符合这些标准的来自两个处理组的奶牛接受了改良的 Ovsynch 方案，添加了 P4 补充剂[控释宫内节育器加 GnRH，控释宫内节育器取出，以及 7 和 8 天后 PGF，第二次 PGF 后 32 h GnRH，以及 GnRH 后 16 至 18 h TAI（G25 NoCL = 53，NoG25 NoCL = 78）]。从 AI 后 18 ± 3 d 开始，每周进行 3 次血清孕酮（P4）浓度测定和卵巢超声检查，直到 TAI 后 1 d（G25 = 46，NoG25 = 44 头奶牛）。在检测到发情时，NoG25 奶牛的重复配种率更高（NoG25 = 53.5%，G25 = 44.6%），而 G25 奶牛的 NPD 时 CL 数更多（83.7%和 71.3%）。在 AI 后 32 d，在检测到发情时，G25 和 NoG25 的 P/AI 相似（38.4%和 42.9%），对于没有 CL 的奶牛的 TAI 服务（40.4%和 36.7%），以及所有服务的综合（39.6%和 39.0%）。然而，在接受 TAI 的奶牛中，G25 奶牛的 P/AI 大于 NoG25 奶牛（40.6%和 32.8%），而在 G25 奶牛中，CL 数更多（40.6%和 32.8%）。与 NoG25 处理组相比，G25 处理组的奶牛有更多的自发排卵或对 GnRH 有反应（70%和 36%），但在 NPD 时，有活性卵泡的比例相似（G25 = 91%，NoG25 = 96%）。NPD 时最大卵泡直径（G25 = 15.0 ± 0.4 mm，NoG25 = 16.5 ± 0.6 mm）和达到≥10 mm 的天数（G25 = 4.0 ± 0.3 d，NoG25 = 5.8 ± 0.6 d）在 NoG25 处理组大于 G25 处理组。对于 NPD 时存在 CL 的奶牛，NPD 后 CL 退化、TAI 后排卵和排卵卵泡直径没有差异。总之，在 NPD 时存在 CL 的奶牛中，去除改良 Resynch-25 方案中的第一个 GnRH，并在 NPD 时不存在 CL 的奶牛中添加 P4 补充的改良 Ovsynch 方案，导致更多的奶牛在检测到发情时再次配种，尽管 NPD 时存在 CL 的奶牛的 P/AI 降低，但怀孕比例相似。
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