do mares bleed when in heat
Typically, during the breeding season, a mare will have a 21-day estrous cycle (the interval from one ovulation to the next). This length will vary between mares and time of the year. The estrous cycle is divided into two periods, estrus and diestrus. Estrus (heat) is the period (usually 4 to 7 days) when the mare is receptive to the stallion. During this period, ovarian follicles grow and develop to between 20 and 50mm in diameter with ovulation occurring 24 to 48 hours before the end of the estrus. Thus, the mare is still showing heat when she ovulates.