Evaluation of the effect of Heatsynch and Ovsynch(two methods of ovulation synchronization) on pregnancy rate in dairy cows

The aim of this study was to evaluate the effect of Heatsynch and Ovsynch(two methods of ovulation synchronization) on pregnancy rate in dairy cows. This study was carried out in a large dairy herd in suburbs of Esfehan province. In total 113 dairy cows with 50-200 days in milk entered in the study. In this experiment cows were alternately assigned to three proups.1) control group (n=50) received no treatment. Cows that were detected in estrous were inseminated by on farm technician.2) Ovsynch group (n=46) received an i.m injection of 10 μg GnRH analog on days 0 and 9 and an i.m injection of 500 μg of PGF2α on day 7, then inseminated 16-20 hour after second GnRH injection. 3) Heatsynch group (n=37) received an i.m injection of 10 μg GnRH analog and 500 μg of PGF2α on days 0 and 7 respectively and then then 1mg estradiol cypiyonate 24 hour after PG injection. Cows that were detected in estrous after estradiol treatment were inseminated as a.m. / p.m.protocol. Timed artificial insemination(TAI) was performed for cows that were not detected in estrous 48 hourafter estradiol treatment.Pregnancy detection were performed on day 30 and between days 40-45 after insemination by ultrasonography and rectal palpation respectively. The differences in Conception rate between three groups were analyzed by using Chi-Square method. Although conception rate in Ovsynchgroup (%41.3) were higher than Heatsynch(%37.8) and control(%36) groups, but there was no significant differences in conception rate between three groups.