Tuyển tập các báo cáo nghiên cứu khoa học quốc tế về bệnh thú y đề tài: Evaluation of the effect of a 3rd GnRH injection administered six days after the 2nd GnRH injection of Ovsynch on the reproductive performance of Japanese black cows | J. Vet. Sci. 2008 9 3 273-279 JOURNAL OF Veterinary Science Evaluation of the effect of a 3rd GnRH injection administered six days after the 2nd GnRH injection of Ovsynch on the reproductive performance of Japanese black cows Abdurraouf Omar Gaja1 Katsumi Hamana2 Chikara Kubota2 Toshiyuki Kojima2 1The United Graduate School of Veterinary Science Yamaguchi University Yamaguchi 753-8515 Japan 2Laboratory of Theriogenology Kagoshima University Kagoshima 890-0065 Japan This study was designed to evaluate the reproductive performance of Japanese black cows following the 3rd injection of gonadotropin releasing hormone GnRH analogue administered concurrently with Ovsynch-based treatment on day 6 day 1 the day of ovulation . In Experiment 1 12 cows were allocated into three groups a control group that was subjected to Ovsynch treatment and then injected with a placebo on day 6 group 1 Ovsynch GnRH which was subjected to Ovsynch treatment and was injected with GnRH analogue on day 6 and group 2 Ovsynch controlled internal drug-release CIDR GnRH which received Ovsynch-CIDR treatment and was injected with GnRH analogue on day 6. Blood collection and ultrasonographic observation of the ovaries were conducted daily. Both treatments induced the formation of an accessory corpus luteum and significantly increased the cross-sectional area of the luteal tissue when compared to the control. However plasma progesterone P4 was significantly higher in the treatment groups than in the control group on days 11 12 17 and 18 in the group 1 and from day 10 to 21 in the group 2. In Experiment 2 41 cows were assigned to the same three groups described above and then artificially inseminated on day 1. The pregnancy rates on day 45 did not differ among groups. In conclusion administration of GnRH analogue on day 6 following Ovsynch-based treatment did not improve the reproductive performance of Japanese black cows even though the P4 concentration was higher in groups that received the GnRH. .
