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 Evaluation of 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 interred in the study. In this experiment cows were alternately assigned to three groups.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 on days 0 and 9 an i.m injection of 10 µg GnRH analog and on day 7 an i.m injection of 500 µg of PGF2? and inseminated 16-20 hour after second GnRH injection.3) Heatsynch group (n=37) received on days 0and 7an i.m injection of 10 µg GnRH analog and 500 µg of PGF2? respectively and 24 hour then 1mg estradiol cypionate. . 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 hour after 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 pregnancy proportion between three groups were analyzed by using Chi-Square method. Although conception rate in Ovsynch group (%41.3) were higher than Heatsynch(%37.8) and control(%36) groups, but there was no significant differences in conception rate between three groups.(p