Measures of estrus detection and pregnancy in dairy cows after administration of gonadotropin-releasing hormone within an estrus synchronization program based on prostaglandin F2 alpha.

The objective of this study was to assess the use of GnRH in a controlled breeding program (7 d prior to the second of two injections of PGF2 alpha, 14 d apart) as a means to improve the expression and detection of estrus, first service conception rate, and overall pregnancy rate of lactating dairy cows. On 17 farms, 348 cows were assigned randomly to either of two breeding programs prior to first insemination. Cows in both programs received PGF2 alpha approximately 2 wk prior to the end of a herd-specific voluntary waiting period for breeding.