The aim of this study was to evaluating strategies for improving dairy cows’ fertility following artificial insemination in summer season using hormonal and antioxidant compounds. For this purpose one hundred high producing, multiparous Holstein cows before the first insemination were randomly assigned to four groups. The treatments were: 1- no injection (control), 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). For this purpose 25 ml of AD3E, 5 ml of GnRH and 1500 IU of hCG were intramuscular injected per cow. Pregnancy rate, number of artificial insemination, open days, concentration of serum progesterone in days 11, 15 and 19 after insemination was determined. In addition, serum cholesterol, triglycerides, VLDL, malondialdehyde (MDA) , glucose, albumin and total protein levels were tested. The results showed that the number of insemination and open days were affected (P 0.05) by treatments. The cows supplemented with vitamin AD3E had higher open days and need more AI for pregnancy. Cumulative pregnancy rates was higher (P 0.05) in GnRH+ hCG group than those the other groups after the second service. However, pregnancy rate in day 120 postpartum was greater (P 0.05) in the control group compared to the groups which received AD3E. Calving rate and type of birth (twins or single) were not affected by the experimental treatments. In pregnant cows, serum progesterone concentration on day 19 after insemination was significantly (P 0.05) higher in the group which received GnRH+ hCG. The concentrations of this hormone in non-pregnant cows were not affected by the treatments. There was no difference in serum triglyceride level, but the concentration of serum cholesterol in GnRH + hCG group was lower (P 0.05) than those the other groups. Injection of GnRH + hCG decreased VLDL (P 0.05) and increased glucose (P 0.05) in compared to groups which received AD3E. MDA concentrations were not affected by the treatments. Significant (P 0.05) reduction in serum total protein and albumin in AD3E group was observed. It was concluded AD3E had negative effect in reproductive performance of dairy cows which were inseminated in summer season and some benefit effect was observed for GnRH+hCG injection. Key words : AD3E, Hormonal supplements, Dairy cow , Progestrone.
