Nutri-Vet Nutritionals Equine Vitamin C formula consists entirely of Ester-C, the patented form of Vitamin C. Ester-C is the only form of vitamin C that is patented, non acidic, and contains metabolites that have been shown to enhance delivery of vitamin C to the cells of the body. Vitamin C is important to the prevention of disease, strengthens the immune system, supports joint health and is an important antioxidant. 5.5 pound 60 day supply tub. DOSAGE: Feed (3/4) ounce per day with regular grain ration, dosage amount based on 1,000 pound horse.