Abstract:

This study was designed to determine the effects of GnRH administration alone at the time of artificial insemination (AI) or in combination with hCG 5 days after GnRH injection on conception rates in postpartum dairy cows. Cows in estrus, without any reproductive health problem, between days 70-120 postpartum were randomly assigned to 3 equal groups. Buserelin acetate (10 µg), was administered at the time of AI to Group I (n=40). Group II (n=40) was administered first with Buserelin acetate (10 μg) at the time of AI and then with 1500 IU of hCG on the 5th day after insemination. Group III was maintained for control purposes and did not receive any treatment. Pregnancy diagnosis was performed on day 30 post-AI by transrectal ultrasonography. Conception rates were 80% (32/40), 80% (32/40), and 57.5% (23/40) in Group I, II and III (P<0.05) respectively In conclusion, it was determined that the use of GnRH alone at the time of AI or additionally the use of hCG on the 5th day after AI increased the pregnancy rates in dairy cows between 70-120 days postpartum, however, there was no difference in pregnancy rates between these two treatments.

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