Synchronization of the ovulation (OvSynch) in beef cattle

Tania Todorova, Tsvetelina Todorova and Iancho Todorov

Abstract: The OvSynch protocol itself has not been successfully used to synchronize beef cows in postpartum anestrus. Recently, various modifications to the ovulation synchronization methods have been developed. One of these is the so-called PreSynch. Cows that are unresponsive to the first injection of GnRH may come to estrus early (36 to 48 hours before prostaglandin injection) or have follicles that are not “synchronized” at the time of prostaglandin injection. Pre-synchronization, as the name indicates, is a protocol that “pre-synchronizes” cows to the early stages of the cycle for optimal response to GnRH treatment, and thus improves ovulation synchronization results (OvSynch).
The experimental cows were divided into three groups of 12 animals each. One group was treated per week. The cows were artificially inseminated. After 35 days, if the cow did not come to spontaneous oestrus, a sonographic examination was performed to determine pregnancy. A total of 36 animals were treated. Out of 36 cows, 17 (47.2%) were pregnant after one treatment and the pregnancies are ongoing.
Nineteen cows, unfertilized after the first synchronization, were exposed 45 days later for another treatment called modified OvSynch. The modified OvSynch includes presynchronization before OvSynch (1 or 2 injections of PGF2α given 14 days apart, with the first injection of OvSynch given 12 to 14 days after the second injection of PGF2α or injections of PGF2α and GnRH every 7 days. Out of nineteen, 11 (57.9%) cows were pregnant 35 days after insemination.

Keywords: beef; cattle; OvSynch; PreSynch

Date published: 2021-10-19