Remarkably, no large scale field study has been conducted to evaluate the reproductive performance of cows synchronized with Presynch-Ovsynch with a 12 versus a 14 d interval from Presynch to the beginning of Ovsynch when cows are inseminated in estrus after Presynch. Thus, the specific objective of this study was to determine if increasing the interval between the Presynch and Ovsynch portion of the Presynch-Ovsynch protocol from 12 to 14 d would reduce the fertility of lactating dairy cows not detected in estrus after Presynch and receiving TAI after completing the Ovsynch protocol.