Thomas J M, Locke J W C, Bishop B E, Abel J M, Ellersieck M R, Yelich J V, Poock S E, Smith M F, Patterson D J
Division of Animal Sciences, University of Missouri, Columbia, MO 65211, United States.
Division of Animal Sciences, University of Missouri, Columbia, MO 65211, United States; College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, United States.
Theriogenology. 2017 Apr 1;92:190-196. doi: 10.1016/j.theriogenology.2017.01.020. Epub 2017 Jan 16.
Two long-term, CIDR-based estrus synchronization protocols were evaluated among Bos indicus-influenced and Bos taurus beef heifers. Treatments were evaluated on the basis of estrous response and pregnancy rate resulting from fixed-time artificial insemination (FTAI), and these outcomes were analyzed retrospectively relative to reproductive tract score (RTS; Scale 1-5) at treatment initiation. Estrus was synchronized for 1139 heifers in three locations, and heifers were assigned to one of two treatments within each location based on RTS. Heifers assigned to the 14-d CIDR-PG protocol received a controlled internal drug release (CIDR) insert (1.38 g progesterone) on Day 0, CIDR removal on Day 14, administration of prostaglandin F (PG; 25 mg im) on Day 30, and administration of gonadotropin-releasing hormone (GnRH; 100 μg im) concurrent with FTAI on Day 33, 66 h after PG. Heifers assigned to the 9-d CIDR-PG protocol received administration of PG concurrent with CIDR insertion on Day 5, administration of PG concurrent with CIDR removal on Day 14, administration of PG on Day 30, and administration of GnRH concurrent with FTAI on Day 33, 66 h after PG. Estrus detection aids were applied at CIDR removal on Day 14 and at PG on Day 30 to evaluate estrous response rate. Mean RTS differed (P < 0.0001) based on biological type due to higher rates of estrous cyclicity (RTS 4 and 5) among Bos taurus heifers (72%; 416/574) than among Bos indicus-influenced heifers (27%; 150/565). The proportion of heifers expressing estrus following CIDR removal was greater (P = 0.01) among heifers assigned to the 14-d CIDR-PG treatment (88%; 492/559) compared to the 9-d CIDR-PG treatment (83%; 480/580). Estrous response following CIDR removal was also higher (P < 0.0001) among Bos taurus (95%; 547/574) compared to Bos indicus-influenced (75%; 425/565) heifers. Rate of estrous response prior to FTAI did not differ significantly based on treatment but was higher (P < 0.0001) among Bos taurus heifers (60%; 344/574) than among Bos indicus-influenced heifers (45%; 253/565). However, the effect of biological type on estrous response was not significant when RTS was included in the model, as RTS significantly (P < 0.0001) affected the rate of estrous response both at CIDR removal and prior to FTAI. Across treatments and biological types, heifers that expressed estrus prior to AI achieved higher (P < 0.0001) AI pregnancy rates than heifers failing to express estrus. Pregnancy rates to FTAI did not differ significantly based on treatment in either biological type. Higher rates of estrous cyclicity among Bos taurus heifers resulted in higher FTAI pregnancy rates among Bos taurus (51%; 290/574) compared to Bos indicus-influenced heifers (39%; 218/565). However, pregnancy rates of respective RTS did not differ based on biological type. In summary, long-term CIDR-based protocols provide a simple, effective method of estrus synchronization in Bos indicus-influenced and Bos taurus beef heifers. Moreover, these results highlight the importance of management practices that result in high rates of estrous cyclicity prior to protocol initiation, particularly among later maturing breeds and biological types.
在受印度瘤牛影响的和欧洲肉牛小母牛中，评估了两种基于阴道海绵栓（CIDR）的长期发情同步方案。根据定时人工授精（FTAI）后的发情反应和妊娠率对处理方法进行评估，并在处理开始时相对于生殖道评分（RTS；1 - 5级）对这些结果进行回顾性分析。在三个地点对1139头小母牛进行发情同步处理，每个地点的小母牛根据RTS被分配到两种处理方法之一。分配到14天CIDR - PG方案的小母牛在第0天接受一个含1.38克孕酮的控制内部药物释放（CIDR）插入物，在第14天取出CIDR，在第30天注射前列腺素F（PG；25毫克，肌肉注射），并在第33天（PG注射66小时后）与FTAI同时注射促性腺激素释放激素（GnRH；100微克，肌肉注射）。分配到9天CIDR - PG方案的小母牛在第5天插入CIDR时同时注射PG，在第14天取出CIDR时同时注射PG，在第30天注射PG，并在第33天（PG注射66小时后）与FTAI同时注射GnRH。在第14天取出CIDR时和第30天注射PG时应用发情检测辅助工具来评估发情反应率。由于欧洲肉牛小母牛（72%；416/574）的发情周期率（RTS 4和5）高于受印度瘤牛影响的小母牛（27%；150/565），基于生物学类型的平均RTS存在差异（P < 0.0001）。与9天CIDR - PG处理（83%；480/580）相比，分配到14天CIDR - PG处理的小母牛在取出CIDR后表现出发情的比例更高（P = 0.01）（88%；492/559）。与受印度瘤牛影响的小母牛（75%；425/565）相比，欧洲肉牛小母牛在取出CIDR后的发情反应也更高（P < 0.0001）（95%；547/574）。FTAI之前的发情反应率在处理方法之间没有显著差异，但欧洲肉牛小母牛（60%；344/574）高于受印度瘤牛影响的小母牛（45%；253/565）（P < 0.0001）。然而，当RTS纳入模型时，生物学类型对发情反应的影响不显著，因为RTS在取出CIDR时和FTAI之前均显著（P < 0.0001）影响发情反应率。在所有处理方法和生物学类型中，在人工授精前表现出发情的小母牛比未表现出发情的小母牛获得更高（P < 0.0001）的人工授精妊娠率。在两种生物学类型中，FTAI的妊娠率在处理方法之间没有显著差异。欧洲肉牛小母牛较高的发情周期率导致其FTAI妊娠率（51%；290/574）高于受印度瘤牛影响的小母牛（39%；218/565）。然而，各自RTS的妊娠率在生物学类型之间没有差异。总之，基于CIDR的长期方案为受印度瘤牛影响的和欧洲肉牛小母牛提供了一种简单、有效的发情同步方法。此外，这些结果突出了在方案开始前导致高发情周期率的管理措施的重要性，特别是在晚熟品种和生物学类型中。
