The most important may be your mare's nutrition. Proper nutrition during gestation is critical to producing a healthy foal. There are three common mistakes in broodmare nutrition. Underfeeding protein and energy during lactation. Nutrient requirements of non-lactating mares before the second trimester of gestation are similar to those of mares at maintenance.
Broodmares can usually get the protein and energy they require from good-quality pasture.
Feeding five or six pounds or more daily of a properly fortified commercial grain mix, such as Southern States Broodmare Special, should provide adequate vitamins and minerals. However, if you feed less commercial grain mix or plain oats than that, you'll need to supplement your mare's diet with additional minerals and vitamins, such as those found in Equimin, to support proper fetal development. Many people believe that in the second half of gestation, mares require much more protein and energy. While mares require slightly more protein and energy then, mineral and vitamin requirements, especially for calcium, phosphorous, magnesium and vitamin A, increase most. Mineral deficiency is not as critical for the mare at this time as it is for the developing fetus.