The Effect of PGF2α-Induction of Estrus on Pregnancy Rates in Mares

In mares, the onset of estrus is routinely induced after a luteolytic dose of a prostaglandin F2alpha analogue. Mares in diestrus with a mature, functional corpus luteum will respond by coming into estrus 3 to 4 days after induction1. Shortening the interestrous interval in mares has an important economic impact on the equine breeding industry. Because the breeding season of the mare is short, timing of insemination and appropriate coordination of endocrine events is critical to pregnancy success and ultimate foaling rates. Several recent studies have reported that the use of prostaglandin analogues is associated with lower pregnancy rates. In this study the induction of estrus with cloprostonol (125-250 ug IM) did not affect pregnancy rates in mares that have ovulatory cycles (n = 461).