Pregnancy of a Mare

the physiological condition of a mare from the time of fertilization until the birth of the foal. The gestation period averages 333 days (307–412). The duration of pregnancy is determined by breed and individual variability, as well as by the mare’s feed and general upkeep. Pregnancy is prolonged if the quality of the animal’s feed deteriorates. Under normal feeding conditions, the weight of a mare increases between 20 and 22 percent during pregnancy. Pregnant mares are given nourishing, easily digestible feed with adequate protein, vitamin, and mineral content. Their diet includes oats, barley, corn, carrots, silage, sprouted grain, and grass meal, as well as grass and legume hay. Bone meal, chalk, calcium phosphate, and trace elements (for example, iodine, copper, and cobalt) are added if the diet lacks minerals. During the summer pregnant mares graze in good pastures; in the winter they are kept and exercised in special corrals. The mares pasture separately from the other horses to prevent bruises and injuries that might cause a miscarriage. Pregnant mares are usually used only for light work.