A Comparative Analysis of Double-Ovsynch and Ovsynch-Heat-Synch Protocols on Pregnancy Rates in Primiparous Dairy Cows

Today, ovulation synchronization methods are widely used to improve fertility in dairy cows. In this regard, this research was conducted in one of the dairy herds in East Azerbaijan province, Iran. The cows were randomly divided into two groups. Ovsynch-Heat-Synch Group: This group included ۳۰ primiparous cows. One month after calving, provided the uterus was clean, the synchronization program commenced. On the first and ninth days, they received GnRH, and on the seventh day, PGF۲α intramuscularly. One week later, they received GnRH again; seven days after that, they received PGF۲α, and ۲۴ hours later, ۱ mg of estradiol benzoate intramuscularly. Cows that showed estrus after the estradiol injection were inseminated using the AM/PM method, while those that did not show estrus ۴۸ hours after the estradiol injection were artificially inseminated (Timed Artificial Insemination, TAI). Double-Ovsynch Group: This group also included ۳۰ primiparous cows. One month after calving, provided the uterus was clean, the synchronization program began. On the first and ninth days, they received GnRH analogue; on day seven, PGF۲α was administered intramuscularly. One week later, they received GnRH analogue again; seven days later, PGF۲α was given, and ۴۸ hours later, they received GnRH analogue intramuscularly. Forced insemination was performed ۱۶ to ۲۴ hours after the last GnRH injection. Pregnancy diagnosis was conducted using ultrasound between days ۳۰ to ۳۵ and by rectal palpation between days ۴۰ to ۴۵ after artificial insemination. The results showed that the fertility rate was ۴۳.۳% (۱۳ cows) in the Ovsynch-Heat-Synch group and ۶۰% (۱۸ cows) in the Double-Ovsynch group. In the statistical analysis, this difference was not significant (p>۰.۰۵). This study indicated that the new Ovsynch-Heat-Synch method does not have a significant superiority over the Double-Ovsynch method.

کلیدواژه ها:

pregnancy rate ، Double-Ovsynch ، Ovsynch Heat-Synch ، cow