IMPROVING THE REPRODUCTIVE PERFORMANCE OF DAIRY COWS WITHGnRH

Abstract

Four experiments were conduced to determine the possibility of improving reproductive performance in early postpartum period by injection of gonadotropin releasing hormone (GnRH) on day 14 or 28 postpartum or prostaglandin F2a (PGF2a) on day 16 postpartum to hasten uterine involution, induce first postpartum estrus, reduce days open and

increase conception rate in dairy cows. In addition, the efficiency of the Ovsynch protocol for synchronization of ovulation using GnRH in combination with PGF2a was also tested. Uterine involution period was significantly shorter in normal and abnormal cows treated with GnRH at day 14 or 28 postpartum. Also, GnRH treatment at 14 or 28 days postpartum led to shortened the first postpartum intervals, reduced days open and increased pregnancy rates at 28 or 60 days post artificial insemination. In addition, treatment with GnRH at 14 or 28 days decreased the number of services required to conceive. Treatment with PGF2a at day 16 postpartum accelerate uterine involution period, induced first observed

estrus at short interval and improved pregnancy rate. Treatment of GnRH in combination with PGF2a led to increase conception rate compared to double injection of PGF2a 14 day apart.