LRH-A3 and HCG increase pregnancy rate during timed artificial insemination in dairy cows.

Abstract

The objective of this study was to use luteinizing hormone-releasing hormone A3 (LRH-A3) and human chorionic gonadotrophin (HCG) to improve pregnancy rate of dairy cows during timed artificial insemination (TAI). In experiment 1, the TAI process (0d, GnRH, 100μg; 7d, PGF2α, 0.4mg; 56hr, GnRH, 100μg; 16hr, AI) was applied to 160 dairy cows on 50th and 60th days after parturition respectively. In experiment 2, 320 postpartum dairy cows were treated with TAI (Group A), TAI+25μg LRH-A3 (Group B), TAI+1,500IU HCG 5days after AI (Group C), and TAI+25μg LRH-A3+1,500IU HCG 5days after AI (Group D). In experiment 3, endometrial cells were treated with HCG. The results showed that TAI did not affect the pregnancy rate, while LRH-A3 and HCG increased the pregnancy rate of the cow. HCG of 5IU/ml and 10IU/ml increased the expressions of leukemia inhibitory factor but decreased those of interleukin-6, epidermal growth factor and vascular endothelial growth factor in endometrial cells. This study provided a plan for the use of LRH-A3 and HCG to increase pregnancy rate during TAI in dairy cows.