Development of bovine estrous synchronization program adapted for small scale Japanese livestock industry

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In order to recover the reproductive function from parturition, hormonal treatment was developed for resumption of ovarian function, and early pregnancy diagnosis together with resynchronization for non-pregnant cows was conducted. These synchronization methods were adapted for the small scale Japanese livestock industry.In Japanese black cows (n=50), fresh check of reproductive organs was conducted on day 30 after parturition, and cows with corpus luteum (CL) was treated with Prostaglandin F2 arufa (PGF2a) and cows without CL was treated with GnRH. 7 days later, progesterone devices (PRID, CIDR) was inserted for vagina for 7-9 days and PGF2a was injected when they were pulled. Estradiol - 17 beta (E2) on 24 h or GnRH on 48h was injected and timed artificial insemination (AI) was performed 16-20 h later. On day 10 after AI, CL was detected for synchronization compliance and early pregnancy test by ultrasonography was conducted on day 28 after AI. In Holstein cows (n=40), similar protoc … More ol was performed, but initial treatment was conducted 2 weeks later followed with progesterone insertion seven days later.In the results, CL was existed in the ovary at fresh check for 35-40% in Japanese black cows and 45-70% in Holsteins, and these were varied depend on the cow group. Timed AI was performed for 97.5% after pull of PRID or CIDR, CL was confirmed 10 days later for 90-95%, and there was no breed difference. Conception rate at early pregnancy test was varied for 35-60% in Japanese black cows and 27-53% in Holsteins, and GnRH treatment was superior to E2 treatment.Ovarian findings in non-pregnant cows at pregnancy test were diestrus 46%, metestrus 15%, proestrus 22%, ovarian cysts 14% and anestrus 3%. Resynchronization was performed for non-pregnant cows in which PGF2a was injected for cows with CL while as CIDR was inserted for cows without CL or ovarian cysts. Estrus was observed within a week after resynchronization, and AI was performed with 40% conception. Conception rate was comparable to control cows, but second AI was performed on day 31.2 after initial AI in resynchronized cows compared to day 56 in controls.In conclusion, early resumption of reproductive tract and ovarian function were keys for the improvement of pregnancy rate in cow herd. Detection of estrus or estrous synchronization and timed AI were necessary for the modern livestock industry. After AI, early pregnancy test by ultrasonography was important for detection of non-pregnant cows, which were subjected for resynchronization and AI. Less