The effect of PGF2α injection in different times on the pregnancy rate in progesterone-based synchronization in Holstein cows

This study investigated the effect of Prostaglandin F2α (PGF2α) injection at different times on pregnancy rate (PR) in Holstein cows undergoing progesterone-based fixed-time artificial insemination (FTAI). Group 1 (G1, n=30): A progesterone releasing intravaginal device (PRID) was placed intravaginally with a gonadotropin-releasing hormone (GnRH) injection on day 0. Eight days later, PGF2α was injected. PRID was removed on the 9th day, and after 60 hours, FTAI was performed with a GnRH injection. Group 2 (G2, n=30): Unlike G1, PGF2α was injected twice, with an interval of 24 hours, 8 and 9 days after the intravaginal placement of PRID. Group 3 (G3, n=30): PGF2α was injected 9 days after the intravaginal placement of PRID. Pregnancy diagnoses were performed by transrectal ultrasonography 45 days after FTAI. Blood samples were taken on the 8th day (for Groups 1 and 2), the 9th day (for Groups 2 and 3, PRID removal day), and on the day of FTAI (for Groups 1, 2 and 3) and serum progesterone (P4) concentration was determined. The pregnancy rate (PR) was 36.67%, 53.33%, and 43.33% in Groups 1, 2, and 3, respectively (P=0.194). In cows with a body condition score (BCS)