Efficacy of the presynch-ovsynch program on some reproductive parameters in postpartum dairy cows

In this study, the aim was to evaluate the presynch-ovsynch protocol on the intervals from calving to first insemination, calving to pregnancy, calving to calving in postpartum lactating cows. Lactating Holstein cows (n=104, 3-5 years old, 450-500 kg BW, 27±3 kg/day average milk yield) were enrolled in the study 26-41 days postpartum. Fifty of them were taken as the control group and 54 of them were the treated experimental group. The control group was not treated and the cows in estrus were inseminated. In the treated group the cows were injected with two PGF2α for presynchronization twice at every 14 days. Fourteen days after the second PGF2α, ovsynch protocol was initiated (GnRH, day 0; PGF2α day 7; GnRH, day 9) and cows were inseminated 12-16 hours after second GnRH injection. Following Al, cows returning to estrus were inseminated at detected heat. Pregnancy diagnosis was performed by ultrasonography at 33-38 days after Al. Calving to first Al (days), calving to pregnancy (day), the number of Al per pregnancy, calving interval (days) for control cows were 96.08±8.20,147.58±9.95, 2.19±0.20 and 430.50±10.90 and for the treated group 70.13±1.13, 101.76±5.70, 1.85+0.12 and386.80±5.70, respectively. Compared to the control group, calving to first Al interval was shorter by 26 days, calving to pregnancy interval by 46 days and the calving interval by 44 days (p<0.001). Number of Al per pregnancy decreased numerically from 2.19 to 1.85. Pregnancy rates for the first Al was 47% forthe control and 43% for the treated cows (p>0.05). As a result, by using the presynch-ovsynch protocol, the need for estrus detection was eliminated and inseminations were performed at a fixed time. Therefore, calving to first Al, calving to pregnancy, calving intervals and the number of Al per pregnancy were improved to the benefit of the farm.