Estrous Synchronization Programs for Dairy Cows and Heifers

Introduction: Although milk production as measured by rolling herd averages has increased markedly for dairy herds in the Western United States over the last decade, reproductive performance of these herds has declined significantly. Average days open have increased by 25 days and fertility has declined as measured by an increase of 0.37 services per conception and first service conception rates have declined from 49.4 to 43.9 percent over the last decade. Heat detection rates for dairy herds at the major dairy record processing centers average slightly over 40 percent. Poor heat detection rates and declining fertility are the primary factors contributing to the reduction in reproductive performance of dairy herds. Two things have evolved over the last decade to help dairy producers improve the reproductive performance their herds. The first factor is better means of measuring the reproductive performance of herds and measuring the response to reproductive interventions. To be able to evaluate the success of various reproductive interventions, producers need a measure of reproductive performance that is current and sensitive to changes. Pregnancy rate has developed as the best measure of herd reproductive performance. The second factor is the advent of new estrous synchronization programs. It is important to be aware of the various programs that are available, to understand what can be expected in outcomes from implementations of the programs and to know the pros and cons of implementing these programs. This paper will review the use pregnancy rate as a tool to measure of reproductive performance of dairy herds and the various estrous synchronization programs for dairy.