Improved fertility of cows failing to respond to resynchronization of ovulation through presynchronization of ovulation or progesterone supplementation during Ovsynch

Abstract

The most widely adopted Resynch program by US dairy herds consists of the initiation of Resynch at 32 d after a previous artificial insemination (AI) regardless of pregnancy status. Seven days later pregnancy status is determined so that non-pregnant cows continue in the protocol to receive their next timed AI (TAI). This program guarantees that cows not detected in estrus are re-inseminated within a specific timeframe after the previous AI (42 ± 3 d if groups of cows are enrolled weekly), reducing the interval between inseminations. Retrospective evaluation of pregnancy per AI (P/AI) for cows that complete the protocol and receive a TAI service has shown that cows without a corpus luteum (CL) at the time of Resynch initiation will have an approximate 50% reduction in fertility when compared with cows that do have a CL. Our objective was to evaluate treatments to increase fertility of TAI services of lactating dairy cows without a CL at the time of the prostaglandin F_2α(PGF) injection of Resynch initiated 32 ± 3 d after AI.