Fertility of lactating Dairy Cows Treated with Ovsynch after Presynthronization injections of PGF_2α and GnRH

摘要

Synchronization of ovulation (Ovsynch) using GnRH and PGF_2α allows control of follicle growth, corpus lu- teum regression, and ovulation, but resulting preg- nancy rates vary. This study examined whether presyn- chronization to allow initiation of Ovsynch during dies- trus would improve pregnancy rates at timed artificial insemination (AI). Lactating dairy cows (n=427), 69 to 75 d postpartum, were randomly assigned to two groups by parity. Control cows received Ovsynch (GnRH, d 0; PGF_2α, d 7; GnRH, d 9; timed AI 16 h after second GnRH).