UltraCruz Natural Vitamin E Immune Support Powder Horse Supplement, 4-lb bag; Help enhance your equine’s immune system function with UltraCruz Natural Vitamin E Horse Supplement. This high-quality vitamin E powder supplement works closely with selenium and vitamin C to support his immune system and protect his body from oxidative stress. It contains vitamin E, a fat-soluble vitamin that may function as an antioxidant that protects cells from free radicals and supports healthy concentrations of elements such as iron, calcium and potassium. Your steed is sure to appreciate this addition to his daily feed.