Determination of the effects of Double-Ovsynch program on some reproductive parameters at different postpartum days in dairy cows

The aim of this study was the evaluate of the effect of Double-Ovsynch protocol on various fertility parameters at different postpartum days in dairy cows.The study was carried out on 51 Holstein cows. The cows were located in the Dikili district of the İzmir province. Group 1 (n =12) was formed with the cows on the 25th day of postpartum. Cows in the group 1 were treated with GnRH on day 0, PGF2? on day 7, GnRH on day 10, GnRH on day 17 and PGF2? on day 24 respectively. The injection of GnRH was applied 56 h after the second PGF2? injection and then timed artificial insemination (TAI) was performed at 16-20 h later (average 18th hour). Animals in the group 2 (n = 12) and group3 (n =12) were formed with the cows on the 32th and 39th day of postpartum respectively. The cows in group 2 and group 3 were subject to application of Double-Ovsynch programme which was used in group1, and the first GnRH injection was admitted as 0th day. On the other hand, no application was made until 40th day of postpartum on the control group (n =15), and artificial insemination was applied on the these cows which show visual signs of the estrus.While the synchronisation rates were changing between %66,66 and %91,66 in the study groups a higher synchronisation rate was observed in the group 2 and group 3 on which late application was performed. The high level serous flow were observed in the study group while few animals show the estrus symptoms at the TAI in these group. The highest pregnancy rates (%58,33) after the first TAI were determined in the cows which the application was started on the 32th and 39th day of postpartum. The highest pregnancy rates after the first TAI in primiparous and multiparous cows were observed on the 32th (%75) and 39th (%75) day of postpartum, respectively.In conclusion, estrus symptoms at the TAI did not observed in cows used Double-ovsynch protocols. In addition to, the highest pregnancy rates after the first TAI was observed in the group 2 and 3 while the highest synchronisation rate was detected in group 3. The highest pregnancy rates after the first TAI in primiparous and multiparous cows were determined in the group 2 and 3, respectively.