Effect of hCG vs. GnRH at the beginning of the Ovsynch on first ovulation and conception rates in cyclic lactating dairy cows.

Ovulatory response to the first GnRH of Ovsynch is a very important factor for determining the outcome of a successful synchronization. The aim of the present study was to develop a protocol to increase the percentage of cows that ovulated in response to the first administration of Ovsynch. This study was designed to compare ovulation rates in response to GnRH or hCG at the beginning of Ovsynch and to evaluate the effects of this manipulation on pregnancy.