Effect GnRH, hCG and AD3E injection on reproductive performance and blood metabolites and progesterone of high producing dairy cows in summer season

Injection of some hormones and antioxidant supplements may improve the reproductive performance of dairy cows during summer season. This study was conducted to evaluate strategies for improving dairy cows’ fertility following artificial insemination in summer season using hormonal and antioxidant compounds. One hundred high producing, multiparous dairy cows were randomly assigned to four groups: 1- Control (without injection of hormone and vitamin), 2- AD3E injection at the time of AI (AD3E), 3- GnRH injection at the time of AI and hCG injection 11 days after AI (GnRH+hCG), and 4- AD3E and GnRH injections at the time of AI and hCG injection 11 days after AI (AD3E+GnRH+hCG). AD3E (25 ml, each ml contain 50000 IU A, 10000 IU D3 and 20 mg E), GnRH (5 ml, each ml contain 5 μg alarin acetate) and hCG (1500 IU) were injected intramuscular. The blood sampling was on days 11, 15 and 19 after AI. The data showed that cows which received vitamin AD3E had more open days and need more insemination services for pregnancy (P<0.05). Cumulative pregnancy rates in the second service and pregnancy rate in day 120 postpartum was affected by the treatments and cows received AD3E had no good condition. Pregnant cows which received GnRH+hCG, had higher (P<0.05) serum progesterone concentration than the other groups on day 19 after AI. The injection of GnRH+hCG reduced (P<0.05) concentration of serum cholesterol and VLDL. However, these cow had higher (P<0.05) glucose, total protein and albumin than that the AD3E group. AD3E injection had adverse effect on reproductive performance of high producing dairy cows in summer season. Although, the injection of GnRH+hCG had no beneficial effect on reproductive performance, but it had some positive effects on blood biochemical parameters.