Effect of Syncro-Mate B Implants (SMB) on Embryo Production by Repeated Superovulation in Japanese Black Cattle

The purpose of this study was to evaluate the effect of repeated superovulation assisted by Syncro-Mate B implants (SMB) on embryo production in Japanese Black cattle. A total of 11 cattle were implanted s. c. with SMB in pinna and injected i. m. with 3mg of norgestomet and 5mg of estradiol valerate at the same time without considering stages of the estrous cycle. Six or seven days after SMB implantation, superovulation treatments were initiated with twice-daily injection of FSH with decreasing dosage manner for 4 days (total FSH 28AU). After 48h or 55h of the first FSH injection, all cattle were injected i. m. with 750μg cloprostenol. All cattle showing estrous behavior were inseminated artificially with frozen semen of Japanese Black bull. Six to eight days later, embryos were collected from uterus by flushing out. The embryo collection was repeated five times at an interval of 28 days. The repeated treatment of superovulation affected the proportion of transferable embryos (P=0.0117) and the number of transferable embryos (P=0.0501). The proportion of transferable embryos at 2nd treatment was significantly higher than that of the other treatment cycle (P