Department of Clinical Sciences, School of Veterinary Medicine, Ferdowsi University of Mashhad, Mashhad, Iran.
Anim Reprod Sci. 2011 Mar;124(1-2):1-6. doi: 10.1016/j.anireprosci.2011.02.013. Epub 2011 Feb 17.
The aim of this study was to evaluate five methods for the resynchronization of estrus in lactating dairy cows. One hundred and seventy-three Holstein cows were assigned at random to five treatments: Ovsynch-24, IPD+Ovsynch-24, Ovsynch-31, Heatsynch, and IPD+Heatsynch. The start of the resynchronization protocols, and all subsequent procedures, was timed in relation to the pre-enrolment AI (PAI) and ranged over 7 days for each treatment. The pregnancy status of all the animals was evaluated by ultrasound examination on day 31±3 PAI. In all treatments, the resynchronized AI (RAI) was at an observed estrus or at a fixed time after the completion of the resynchronization procedures. Cows were observed for estrus thrice daily and those observed in estrus were inseminated according to the AM-PM rule. Those cows diagnosed as not pregnant and not observed in estrus were inseminated at a fixed time. The average proportion of cows with an active CL was 31.2% (54/173) on day 14 PAI, 22.0% (38/173) on day 21 PAI, and 18.5% (32/173) on day 24 PAI (NS). The incidence of luteolysis averaged 12.7% (22/173) from day 21 to 24, and 28.9% (50/173) from day 14 to 24. The differences between individual treatments were not significant but there was a significantly greater incidence of luteolysis (P<0.0009) from day 14 to 21 for the IPD treatments combined (30.3%; 24/63) than for the non-IPD treatments combined (26.6%; 17/110). Conception rates at day 31 PAI ranged from 16.6% to 42.1% (NS), and at day 61 PAI ranged from 16.6% to 37.1% (NS). Also conception rates at day 31 and 61 RAI ranged from 5% to 25% (NS). Pregnancy losses between days 31 and 61 PAI varied from 0 to 25.0% (NS) between treatments for the pre-enrollment AI but were 0% for all treatments for the resynchronized AI. It was concluded that using IPD, PGF2α, estradiol and GnRH in different resynchronization methods had no effects on conception rate in this study. Also conception rate was not significantly different when resynchronization programs began before ultrasonographic examination for pregnancy diagnosis. Using IPD did not reduce luteolysis during resynchronization programs and estrus detection rates were similar among treatment groups.
本研究旨在评估五种方法对泌乳奶牛的同期发情效果。将 173 头荷斯坦奶牛随机分为五组：Ovsynch-24、IPD+Ovsynch-24、Ovsynch-31、Heatsynch 和 IPD+Heatsynch。每个处理组的同期发情方案的启动时间以及随后的所有程序都与预配种人工授精（PAI）相关，每个处理组的时间跨度为 7 天。所有动物的妊娠状态均在 PAI 后 31±3 天通过超声检查进行评估。在所有处理组中，复配人工授精（RAI）均在观察到发情或在同期发情程序完成后的固定时间进行。奶牛每天观察三次发情，并按照 AM-PM 规则对观察到发情的奶牛进行授精。那些未怀孕且未观察到发情的奶牛则在固定时间进行授精。在 PAI 后 14 天，有活性黄体的奶牛比例平均为 31.2%（54/173），在 PAI 后 21 天为 22.0%（38/173），在 PAI 后 24 天为 18.5%（32/173）（无统计学差异）。从 PAI 后 21 天到 24 天，黄体溶解的发生率平均为 12.7%（22/173），从 PAI 后 14 天到 24 天为 28.9%（50/173）。各个处理组之间的差异没有统计学意义，但在 IPD 处理组（30.3%，24/63）中，从 PAI 后 14 天到 21 天黄体溶解的发生率显著高于非 IPD 处理组（26.6%，17/110）（P<0.0009）。PAI 后 31 天的妊娠率为 16.6%至 42.1%（无统计学差异），PAI 后 61 天的妊娠率为 16.6%至 37.1%（无统计学差异）。RAI 后 31 天和 61 天的妊娠率也在 5%至 25%（无统计学差异）之间。PAI 后 31 天至 61 天的妊娠损失在不同处理组之间的变化范围为 0 至 25.0%（无统计学差异），但在所有处理组中，用于同期发情的人工授精后均为 0%。研究结论为，在本研究中，使用 PGF2α、Estradiol 和 GnRH 等不同同期发情方法对妊娠率没有影响。此外，在开始超声妊娠诊断前，同期发情方案开始时间对妊娠率也没有显著影响。使用 IPD 并没有减少同期发情过程中的黄体溶解，并且各组的发情检测率相似。
