Departamento de Zootecnia, Instituto de Ciências Sociais, Educação e Zootecnia, Universidade Federal do Amazonas, AM, 69152-240, Parintins, Brazil.
Department of Animal Science, University of California, Davis, CA, 95616, USA.
Trop Anim Health Prod. 2023 Jul 15;55(4):270. doi: 10.1007/s11250-023-03677-2.
This study aimed to evaluate the reproductive performance of Nellore suckled cows inseminated 55 (n = 304) or 65 (n = 296) h after progesterone (P4) removal in a 7-d protocol. The protocol consisted of the insertion of a device with 2 g of P4 and 2 mg of estradiol benzoate on d 0, with the device remaining in the cows for 7 d. Cows in the 55-h treatment had the P4 device removed in the morning, while cows in the 65-h treatment had the P4 device removed in the afternoon. At P4 removal, cows received intramuscularly 300 IU of eCG, 0.6 mg of estradiol cypionate and 0.52 mg cloprostenol sodium. Artificial insemination was performed according to treatments (55 vs. 65 h after P4 removal). The results of the study showed that the estrus detection rate (69% vs 65%) and pregnancy per AI (P/AI; 49% vs 49%) did no differ in cows inseminated 55 or 65 h after P4 removal, respectively. Furthermore, ovulation rate, the diameter of the largest follicle at the time of AI, and P4 concentration after AI were not affected by treatments. The probability of P/AI was not affected by parity, BCS, age, diameter of largest follicle at AI, days postpartum, BW and time to AI. This study suggests that performing AI from 55 to 65 h after the P4 removal in the 7-d-P4 protocol did not affect the reproductive performance in Nellore cows, and opens the possibility for producers to take more time to perform AI of cows in the field without affecting P/AI.
本研究旨在评估在 7 天孕酮（P4）方案中，P4 去除后 55（n=304）或 65（n=296）小时给内罗尔哺乳期奶牛配种对繁殖性能的影响。该方案包括在 d0 插入一个装置，其中含有 2g 的 P4 和 2mg 的苯甲酸雌二醇，该装置在奶牛体内保留 7 天。55 小时处理组的奶牛在早上去除 P4 装置，而 65 小时处理组的奶牛在下午去除 P4 装置。在 P4 去除时，奶牛肌肉内注射 300IU 的 eCG、0.6mg 的雌二醇环戊丙酸酯和 0.52mg 的氯前列烯醇钠。根据处理（P4 去除后 55 与 65 小时）进行人工授精。研究结果表明，发情检测率（69%对 65%）和每 AI 受胎率（P/AI；49%对 49%）在 P4 去除后 55 或 65 小时授精的奶牛中没有差异。此外，排卵率、AI 时最大卵泡直径和 AI 后 P4 浓度不受处理影响。P/AI 的概率不受胎次、BCS、年龄、AI 时最大卵泡直径、产后天数、BW 和 AI 时间的影响。本研究表明，在 7 天 P4 方案中，P4 去除后 55 至 65 小时进行 AI 不会影响内罗尔奶牛的繁殖性能，为生产者在不影响 P/AI 的情况下，在现场为更多的奶牛进行 AI 提供了更多的时间。
