Reproduction Vets

Mares reach puberty at about 18 months of age and undergo an estrous, or heat, cycle. Mares go into heat repeatedly during the breeding season, which usually continues while the days are long, and ends when winter approaches. Exposing mares to increasing periods of artificial light can get the breeding season started earlier. During the breeding season, mares ovulate regularly every 3 weeks, but they are in heat and receptive to a stallion for only 2 to 8 days. Heat is generally longer early in the season (spring) and only 2 to 3 days in late June. Pregnant mares generally have a single foal; twins are rare. Foals can see and stand to suckle soon after birth.