Abstract:

In this study, the effect of a single dose of GnRH on d 13 or progesterone implant for 7 days between d 13 and 20 on plasma progesterone levels and pregnancy rates on cryopreserved embryo transferred cows were investigated. Synchronized 48 Brown Swiss recipient cows were used as animal material. Seven days after estrus detection, cryopreserved cattle embryos were transferred into recipients and cows were assigned randomly into three groups. In GnRH group (n=16), cows were intramuscularly injected 10 g buserelin acetate on d 13. In Implant group (n=16), ear implants containing 3 mg norgestomet were applied for 7 days between d 13 and 20. Control group (n=16) animals were intramuscularly injected 2 ml of saline on d 13. Progesterone levels in Implant group on d 16 and 20 were higher than that of in GnRH and Control groups (p<0.05). Pregnancy rates on d 28 were 43.75% (7/16), 50% (8/16) and 18.75% (3/16) in GnRH, Implant and Control groups, respectively, and it was higher in Implant group than that of in control group (p=0.06). In conclusion, progesterone supplementation between d 13 and 20 via ear implant increased the progesterone levels on d 16 and 20, and increased pregnancy rate compared to Control group

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