Comparison of two estrus synchronization programs in a large, confinement-housed dairy herd.

Objective: To compare pregnancy rates, seasonal effects, and economic benefits of 2 estrus synchronization programs for a confinement-housed dairy herd.

Design: Prospective cohort study.

Animals: 200 lactating Holstein cows.

Procedure: Cows eligible for breeding were palpated per rectum and randomly assigned to 2 treatment groups during 4 seasonal periods. Cows in one group (Ovsynch) received injections of gonadotropin releasing hormone (GnRH) on day 0, prostaglandin F2 alpha on day 7, and a second injection of GnRH on day 8. Cows in the other group (PP) that had a palpable corpus luteum were given prostaglandin F2 alpha. Estrus detection was not performed on the Ovsynch cows, which were artificially inseminated at a predetermined time after the second GnRH injection. Cows in the PP group were observed for signs of estrus, and only those that were detected in estrus were inseminated.

Results: Pregnancy rates and insemination rates were significantly improved for cows in the Ovsynch group, compared with cows in the PP group.

Clinical Implications: The Ovsynch program was an economically advantageous method for controlling reproduction that resulted in pregnancies without the need for estrus detection.