White Stephanie S, Kasimanickam Ramanathan K, Kasimanickam Vanmathy R
Department of Veterinary Clinical Sciences, Washington State University, Pullman, Washington, USA.
Department of Veterinary Clinical Sciences, Washington State University, Pullman, Washington, USA.
Theriogenology. 2016 Aug;86(3):785-90. doi: 10.1016/j.theriogenology.2016.02.032. Epub 2016 Mar 8.
Timed artificial insemination protocols in beef cattle are designed to synchronize ovulation in a greater proportion of females while simultaneously achieving acceptable pregnancy rates and a concise calving season. Protocols achieving such goals reduce time and labor associated with estrus detection and make advanced reproductive technologies implementable for beef producers. The objective of the study was to determine the effect of three different PGF2α (PGF) dosage schemes on artificial insemination (AI) pregnancy rates in beef heifers. We hypothesized that two doses of PGF administered concurrently at the time of controlled internal drug release (CIDR) removal would attain similar pregnancy rates compared with two doses given 6-hours apart-one at CIDR removal and the next 6 hours later in the 5-day CO-Synch progesterone-based synchronization protocol. Angus heifers (n = 875) at six locations in Washington, Idaho, and Oregon states were included in this study. Heifers within locations were assigned a body condition score (BCS). All heifers received a CIDR (1.38 g of progesterone) and 100 μg IM of GnRH on Day 0. The CIDRs were removed on Day 5, heifers were randomly allocated to one of three protocol groups: 1PGF (n = 291), received 25 mg IM of dinoprost (PGF); 2CO-PGF (n = 291), received 50 mg IM of dinoprost at CIDR removal, 2PGF (n = 293), received 25 mg IM of dinoprost at CIDR removal, and an additional 25 mg IM of dinoprost 6 hours later. Each heifer was given GnRH (100 μg, IM) and artificially inseminated at 56 hours after CIDR removal. Heifers were examined for pregnancy status between 50 and 70 days after AI to determine time of conception. A mixed-model procedure (PROC GLIMMIX of SAS) was used to evaluate the effect of treatments (1PGF, 2CO-PGF, and 2PGF) on AI pregnancy rates. Models included were treatments, BCS categories (≤5 and >5), and treatment by BCS category interaction. Location (state), handling facilities, handlers, inseminators, and AI sires were included as a random effect in the model. The 2PGF group had greater AI pregnancy rate of 63.6% (185/291), compared with the 2CO-PGF group at 51.9% (151/291) and 1PGF group at 54.9% (161/293; P < 0.001). An AI pregnancy rate of 50% (104/208) was observed for heifers with BCS less than or equal to 5 versus 58.9% (393/667) for heifers with BCS greater than 5 (P < 0.05). Location did not influence the AI pregnancy rate (P > 0.1). In conclusion, beef heifers received two 25-mg doses of PGF at 6-hour interval on Day 5 at CIDR insert removal in a 5-day CO-Synch + CIDR synchronization protocols achieved greater pregnancy compared with heifers received 50 mg of PGF concurrently at CIDR removal.
肉牛的定时人工授精方案旨在使更大比例的母牛排卵同步，同时实现可接受的妊娠率和紧凑的产犊季节。实现这些目标的方案减少了与发情检测相关的时间和劳动力，并使先进的繁殖技术能够应用于肉牛生产者。本研究的目的是确定三种不同的前列腺素F2α（PGF）剂量方案对肉牛小母牛人工授精（AI）妊娠率的影响。我们假设，在取出控制内部药物释放（CIDR）时同时给予两剂PGF，与在基于5天CO-Synch孕酮的同步方案中，在取出CIDR时给予一剂，6小时后再给予一剂相比，妊娠率相似。华盛顿州、爱达荷州和俄勒冈州六个地点的安格斯小母牛（n = 875）被纳入本研究。各地点内的小母牛被评定体况评分（BCS）。所有小母牛在第0天接受一个CIDR（1.38 g孕酮）和100 μg肌肉注射促性腺激素释放激素（GnRH）。CIDR在第5天取出，小母牛被随机分配到三个方案组之一：1PGF（n = 291），接受25 mg肌肉注射氯前列醇（PGF）；2CO-PGF（n = 291），在取出CIDR时接受50 mg肌肉注射氯前列醇，2PGF（n = 293），在取出CIDR时接受25 mg肌肉注射氯前列醇，并在6小时后再接受25 mg肌肉注射氯前列醇。每头小母牛在取出CIDR后56小时给予GnRH（100 μg，肌肉注射）并进行人工授精。在人工授精后50至70天检查小母牛的妊娠状态，以确定受孕时间。采用混合模型程序（SAS的PROC GLIMMIX）评估处理（1PGF、2CO-PGF和2PGF）对人工授精妊娠率的影响。纳入的模型包括处理、BCS类别（≤5和>5）以及处理与BCS类别的交互作用。地点（州）、处理设施、处理人员、输精员和人工授精公牛作为随机效应纳入模型。2PGF组的人工授精妊娠率更高，为63.6%（185/291），而2CO-PGF组为51.9%（151/291），1PGF组为54.9%（161/293；P < 0.001）。体况评分小于或等于5的小母牛人工授精妊娠率为50%（104/208），而体况评分大于5的小母牛为58.9%（393/667；P < 0.05）。地点对人工授精妊娠率没有影响（P > 0.1）。总之，在5天CO-Synch + CIDR同步方案中，在取出CIDR时于第5天每隔6小时给肉牛小母牛注射两剂25 mg的PGF，与在取出CIDR时同时注射50 mg PGF的小母牛相比，妊娠率更高。
