The Ovsynch® protocol is a breeding strategy to reduce the need for estrus detection. The protocol is composed of an injection of GnRH to induce ovulation of the dominant follicle and synchronize new emergence of a follicle wave. Seven days later, PGF2a is given to regress the original and/or the newly formed CL and is followed 48 h later with a second injection of GnRH to induce a synchronized ovulation between 24 and 34 h. A TAI is carried out at 12 to 16 h after the second GnRH injection (Fig. 1). This protocol has been implemented successfully worldwide as a strategy for TAI at the first postpartum service, as well as for reinsemination of nonpregnant cows. Although the Ovsynch® protocol allows for TAI without the need for estrus detection, approximately 10 to 15% of the cows will display signs of estrus during the protocol, and they should be inseminated promptly if maximum pregnancy rate (PR) is to be achieved (Fig. 1).

When lactating dairy cows were assigned randomly to either the Ovsynch® protocol or inseminated based on estrus detection with periodic use of PGF2a,[1] median days postpartum to first insemination (54 vs. 83) and days postpartum to pregnancy (99 vs. 118) were less for cows in Ovsynch® compared to cows inseminated following estrus detection. When measuring PR, the Ovsynch® protocol for a first service TAI was as effective as inseminating cows at detected estrus following a synchronization protocol of GnRH and PGF2a given 7 days apart.[2]

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