Mares have a gestation period of about 340 days. Because of this relatively long pregnancy, they must become pregnant again shortly after giving birth in order to produce a foal at about the same time each year if this is desired by the owner or …

Mares cycle when days are long and there is abundant daylight during most of the day, meaning that under normal circumstances, they cycle in the Spring, Summer and Fall. Mares do not cycle in Winter when daylight is short; this is known as anestr …