Note: There can be a seasonal effect with mares due to
foal in late winter and early spring which may result in carrying their foals
approximately 5 to 10 days longer than mares foaling late spring or summer.
Exposing pregnant mares to artificial lighting regimens can reduce gestation by
an average of ten days. There are many other factors that may influence
gestational length include sex of the foal, maternal nutrition, ingested toxins
and environmental stresses.