Effect of PGF2α and GnRH Injections Applied Before Ovsynch on Pregnancy Rates in Cows and Heifers

Abstract

The objective of the study was to investigate the effect of PGF2α and GnRH injections applied before Ovsynch protocol (G6G) on pregnancy rates in cows and heifers. Totally, 196 Holstein cows in postpartum 50-100 days and 169 Holstein heifers were used. Animals in group 1 (Control: 40 cows, 40 heifers) were inseminated artificially in their standing heat without hormonal treatment. In group 2 (Ovsynch: 37 cows, 80 heifers), Ovsynch protocol (day 0, 10 μg buserelin acetate, intramuscular (IM); day 7, 500 μg cloprostenol, IM; day 9, 10 μg buserelin acetate, IM; 16 h later following last injection, artificial insemination) was applied. In group 3 (G6G: 119 cows, 49 heifers), 500 μg cloprostenol on day 0 and 10 μg buserelin acetate on day 2 were injected and Ovsynch protocol was performed 6 days later following last injection. Pregnancy rates in cows and heifers were detected 57.50-60.00%; 37.83-32.50% and 53.78-59.18% in 1st, 2nd and 3rd groups, respectively. The pregnancy rate in G6G protocol was significantly higher than those of Ovsynch protocol, in heifers (P<0.05). In conclusion, it is suggested that G6G protocol is an important approach in control of reproduction in heifers and lactating dairy cows instead of Ovsynch protocol which causes low pregnancy rates. Moreover, the present study provides evidence that G6G protocol has higher pregnancy rates in Holstein heifers.