Follicular growth and estradiol concentrations in foaling and nonparturient mares

Plasma estradiol concentration and follicular development were evaluated da ily during the first postpartum estrus and the subsequent cycle of five foa ling mares. For comparison, one estrous cycle was monitored in the same fas hion for five nonparturient mares. The first postpartum estrous cycles were shorter but similar to non-pregnant cycles in ovarian steroid production a nd follicular activity. However, estradiol production from postpartum folli cles was lower per mm follicular diameter than from follicles in nonpregnan t cycles (p<0.05).