Leão Iago Matheus Rosa, Carbajal Anthony, Narciso César, Consentini Carlos Eduardo Cardoso, Sartori Roberto, Nascimento Martins João Paulo
Department of Medical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI 53706.
Sequoia Veterinary Services, Tulare, CA 93274.
JDS Commun. 2024 Apr 20;5(6):695-699. doi: 10.3168/jdsc.2023-0540. eCollection 2024 Nov.
We investigated the effect of an additional GnRH 2 d after initiation of resynchronization on d 25 post-AI on the proportion of cows without a corpus luteum (CL) at nonpregnancy diagnosis (NPD) and pregnancy per AI (P/AI) of cows with a CL at NPD that were reinseminated. Once per week, cows that were inseminated 25 d earlier were randomly assigned to receive either a GnRH treatment only (G25) or GnRH on this day and 2 d later (G25&27). Pregnancy diagnosis and CL presence were determined d 32 post-AI using ultrasonography. Nonpregnant cows with a CL were enrolled in different strategies for resynchronization of ovulation according to parity (primiparous or multiparous) and CL size. Primiparous and multiparous cows with a CL ≥20 mm in diameter continued Resynch-25 (PGF on d 32; PGF on d 33; GnRH on d 34; and AI on d 35). Multiparous cows with CL <20 mm restarted a modified Ovsynch at NPD (GnRH - 7 d - PGF - 1 d - PGF - 1 d - GnRH - 1 d - AI). Primiparous cows with CL diameter <20 mm started an Ovsynch+CIDR protocol on the day of NPD (GnRH + CIDR inserted - 7 d - PGF + CIDR removed - 1 d - PGF - 1 d - GnRH - 1 d - AI). Cows without a CL were not enrolled in any resynchronization program for a week and were excluded from fertility analyses. In multiparous cows only, the additional d 27 GnRH treatment was associated with a decreased P/AI 32 d and 102 d post-AI for the AI before treatment. The overall proportion of nonpregnant cows without CL did not differ between treatments. Yet, the GnRH treatment 27 d after AI tended to increase the proportion of overall nonpregnant cows with CL <20 mm at NPD. Treatment did not affect fertility parameters of primiparous cows with a CL ≥20 mm that continued Resynch-25 at NPD. Primiparous cows in G25&27 with CL <20 mm and submitted to Ovsynch+CIDR at NPD tended to have decreased P/AI 102 d after AI and calving/AI. When fertility parameters of primiparous cows with a CL independent of size at NPD were analyzed combined, no effect of treatment was observed. Treatment did not affect fertility of multiparous cows with CL <20 mm enrolled in Ovsynch at NPD. Multiparous cows in the G25&27 group that had a CL ≥20 mm and continued Resynch-25 at NPD tended to have a greater calving/AI due to a decreased total pregnancy loss. In summary, no treatment effect was observed on the overall fertility of primiparous cows with CL at NPD. In multiparous cows, G25&27 was associated with a decreased fertility of the previous AI, but it tended to increase calving/AI for multiparous cows with CL at NPD by decreasing the total pregnancy loss for the AI after treatment.
我们研究了在人工授精（AI）后第25天开始重新同步化的第2天额外使用促性腺激素释放激素（GnRH），对未妊娠诊断（NPD）时无黄体（CL）的母牛比例以及NPD时有CL且再次输精的母牛的每人工授精妊娠率（P/AI）的影响。每周一次，将25天前输精的母牛随机分为仅接受GnRH处理组（G25）或在当天及2天后接受GnRH处理组（G25&27）。在AI后第32天使用超声检查确定妊娠诊断和CL的存在情况。有CL的未妊娠母牛根据胎次（初产或经产）和CL大小采用不同的排卵重新同步化策略。直径≥20 mm的初产和经产有CL的母牛继续进行Resynch - 25方案（第32天使用前列腺素F2α（PGF）；第33天使用PGF；第34天使用GnRH；第35天进行AI）。CL<20 mm的经产母牛在NPD时重新开始改良的Ovsynch方案（GnRH - 7天 - PGF - 1天 - PGF - 1天 - GnRH - 1天 - AI）。CL直径<20 mm的初产母牛在NPD当天开始Ovsynch + 阴道孕酮释放装置（CIDR）方案（GnRH + 插入CIDR - 7天 - PGF + 取出CIDR - 1天 - PGF - 1天 - GnRH - 1天 - AI）。无CL的母牛一周内不参与任何重新同步化程序，并被排除在生育力分析之外。仅在经产母牛中，额外的第27天GnRH处理与处理前AI后第32天和第102天的P/AI降低有关。各处理组中无CL的未妊娠母牛的总体比例无差异。然而，AI后第27天的GnRH处理倾向于增加NPD时CL<20 mm的总体未妊娠母牛的比例。处理对NPD时继续进行Resynch - 25的CL≥20 mm的初产母牛的生育力参数无影响。G25&27组中CL<且在NPD时接受Ovsynch + CIDR的初产母牛，AI后第102天的P/AI和产犊/AI倾向于降低。当综合分析NPD时CL大小无关的初产母牛的生育力参数时，未观察到处理的影响。处理对NPD时参与Ovsynch的CL<20 mm的经产母牛的生育力无影响。G25&27组中CL≥20 mm且在NPD时继续进行Resynch - 25的经产母牛，由于总妊娠损失减少，产犊/AI倾向于更高。总之，未观察到处理对NPD时有CL的初产母牛的总体生育力有影响。在经产母牛中，G25&27与前一次AI的生育力降低有关，但通过减少处理后AI的总妊娠损失，它倾向于提高NPD时有CL的经产母牛的产犊/AI。
