Abstract:

The objective of this study was to determine the effects of progesterone (PRID) application and gonadotropin-releasing hormone (GnRH) injection after artificial insemination on serum progesterone concentration and pregnancy rates in repeat breeder cows. In group 1, repeat breeder cows received an injection of GnRH on day 12 after artificial insemination. In group 2, repeat breeder cows received PRID from day 4 to day 11; group 3 received PRID from day 11 to day 18. Blood samples were obtained from all treated cows to assay serum progesterone concentrations on application days, 7 days after application, and 21 days after artificial insemination. In the control group repeat breeder cows did not receive any treatment. Blood samples were obtained from all control repeat breeder cows periodically after artificial insemination. Pregnancy rates were 20% in group 1, 26.6% in group 2, 40% in group 3, and 20% in the control group. Serum progesterone concentrations were significantly higher in group 1 and group 3 (P < 0.05) than the control group, 7 days after application. Application of PRID and GnRH after artificial insemination did not significantly improve pregnancy rates, despite the fact that serum progesterone concentrations were higher in treatment groups.

Keywords: