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

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 (0 d, GnRH, 100 mu g; 7 d, PGF2 alpha, 0.4 mg; 56 hr, GnRH, 100 mu g; 16 hr, 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 + 25 mu g LRH-A3 (Group B), TAI + 1,500 IU HCG 5 days after AI (Group C), and TAI + 25 mu g LRH-A3 + 1,500 IU HCG 5 days 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 5 IU/ml and 10 IU/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.

Automated summary

This study aimed to improve pregnancy rates of dairy cows during timed artificial insemination (TAI) by using LRH-A3 and HCG. Results showed that while TAI did not affect pregnancy rates, LRH-A3 and HCG increased pregnancy rates in cows. HCG treatment affected gene expressions in endometrial cells.