Wiltbank Milo C, Baez Giovanni M, Cochrane Fenella, Barletta Rafael V, Trayford Cheryl R, Joseph Robert T
Department of Dairy Science, University of Wisconsin, Madison 53706.
Department of Dairy Science, University of Wisconsin, Madison 53706; Universidad Francisco de Paula Santander, Cucuta 540003, Colombia.
J Dairy Sci. 2015 Dec;98(12):8644-54. doi: 10.3168/jds.2015-9353.
The main objective of this study was to evaluate the effect of a second treatment with prostaglandin F2α (PGF) during Ovsynch on regression of the corpus luteum (CL) and on fertility to the timed artificial insemination. Two experiments were performed. In both experiments, cows were randomized to receive (1) no additional treatments with PGF=1 PGF, or (2) a second PGF treatment at 24h after the first PGF treatment=2 PGF. The first experiment (n=344 synchronized lactating dairy cows that received artificial insemination at 81±3d in milk) used the Double-Ovsynch protocol for synchronizing ovulation. Blood samples were collected at the PGF and final GnRH treatments (72 and 16h before timed artificial insemination) during the breeding Ovsynch protocol, to determine CL regression in response to the protocol. Treatment with 2 PGF increased CL regression from 83.0% with 1 PGF to 97.0% with 2 PGF. The effect of 2 PGF on CL regression was observed in both primiparous and multiparous cows. Cows with lower (2.0 to 4.8ng/mL) versus greater (4.9 to 12.0ng/mL) circulating progesterone at the time of PGF had lower percentage of cows with complete CL regression after 1 PGF (66.7 vs. 88.1%) but not after 2 PGF (95.1 vs. 97.6%). Experiment 2 used 2,148 lactating dairy cows on 11 dairy farms in 4 different regions of the United States. Cows were synchronized with Ovsynch and received timed artificial insemination at 60±3d in milk. Cows that received 2 PGF had a tendency for increased pregnancies per artificial insemination (P/AI) compared with cows with 1 PGF (36.1 vs. 33.3%). This tendency for improvement in P/AI was observed in multiparous but not in primiparous cows. Combining data from the 2 experiments indicated a 9.45% relative increase in P/AI for cows receiving 2 compared with 1 PGF (37.6 vs. 34.4%) with the increase in P/AI observed in multiparous but not in primiparous cows. Thus, a second PGF treatment in Ovsynch-type protocols can increase pregnancy success by about 10%, primarily due to enhanced fertility in multiparous cows.
本研究的主要目的是评估在同期发情程序中第二次使用前列腺素F2α（PGF）处理对黄体（CL）退化以及定时人工授精受胎率的影响。进行了两项试验。在两项试验中，奶牛被随机分为两组，分别接受：（1）不再额外使用PGF（=1次PGF），或（2）在首次PGF处理后24小时进行第二次PGF处理（=2次PGF）。第一项试验（n = 344头处于泌乳期且在产奶81±3天接受人工授精的同期发情奶牛）采用双同期发情方案来同步排卵。在繁殖同期发情方案期间，于PGF和最后一次促性腺激素释放激素（GnRH）处理时（定时人工授精前72小时和16小时）采集血样，以确定对该方案的黄体退化情况。2次PGF处理使黄体退化率从1次PGF处理时的83.0%提高到2次PGF处理时的97.0%。在初产和经产奶牛中均观察到了2次PGF处理对黄体退化的影响。在PGF处理时，循环孕酮水平较低（2.0至4.8ng/mL）的奶牛与较高（4.9至12.0ng/mL）的奶牛相比，1次PGF处理后黄体完全退化的奶牛百分比更低（66.7%对88.1%），但2次PGF处理后并非如此（95.1%对97.6%）。试验2在美国4个不同地区的11个奶牛场使用了2148头泌乳奶牛。奶牛采用同期发情方案进行同步处理，并在产奶60±3天接受定时人工授精。与接受1次PGF的奶牛相比，接受2次PGF的奶牛每次人工授精的妊娠率（P/AI）有增加的趋势（36.1%对33.3%）。这种P/AI提高的趋势在经产奶牛中观察到了，但在初产奶牛中未观察到。将两项试验的数据合并表明，与接受1次PGF的奶牛相比，接受2次PGF的奶牛P/AI相对增加了9.45%（37.6%对34.4%），且P/AI的增加在经产奶牛中观察到了，但在初产奶牛中未观察到。因此，在同期发情类型的方案中进行第二次PGF处理可使妊娠成功率提高约10%，主要是由于经产奶牛的繁殖力增强。
