Synchronization of Ovulation and Fixed-Time Insemination for Improvement of Conception Rate in Dairy Herds with Poor Estrus Detection Efficiency

Abstract

Objectives of this study were to examine effects of GnRH-PGF2α-GnRH treatment and fixed-time AI (OVSYNCH) on the conception rate in Holstein-Friesian dairy herds with poor estrus detection efficiency in Eastern region of Hokkaido. In the first experiment ten cows, which were found to have normal ovarian cycle, were first injected intramuscularly with 100 μg fertirelin acetate (an analog of GnRH), followed by an intramuscular injection of 25 mg dinoprost (PGF2α-THAM) at an interval of 7 days. A second dose of fertirelin acetate was administered 48 h after the dinoprost injection. All cows were artificially inseminated (AI) 24 h after the second fertirelin injection. Milk progesterone profile and ultrasonography indicated that ovulation was synchronized in all 10 cows, and 70% cows conceived. In the second experiment a total of 336 cows with postpartum anestrus were divided into two groups. A group of 185 cows were subjected for OVSYNCH, while the other group of 139 anestrus cows with functional corpus luteum were given 25 mg dinoprost and inseminated artificially 3 days after the dinoprost treatment and 12 anestrus cows with inactive ovaries were injected with 100 μg fertirelin acetate and inseminated artificially at heat and inserved as a control. Of 185 cows treated with OVSYNCH, 153 cows were inseminated artificially and 82 cows (53.6%) conceived. A conception rate in control cows treated with dinoprost and bred 3 days later was 20.9%. The OVSYNCH has been proved to be a useful tool for improving reproductive performance in dairy herds with a low estrus detection rate.