Epsom Salt (Magnesium Sulfate) Magnesium plays an important part in the support of normal muscle and nervous systems. Horses deficient in this important mineral may have a poor tolerance to work and may be sensitive to environmental stress. AniMed's Epsom Salt is an excellent source of dietary magnesium for horses of all classes when a supplemental source of magnesium is needed. | AniMed Epsom Salt Supplement | Size 5 lb