Message : Required fields Vitamins are organic compounds that are necessary for vital functions. Most animal diets provide sufficient vitamins for adequate health, but under some management conditions, disease states, or seasonal alterations, it may be necessary to supplement vitamins. Vitamins are broken down into fat-soluble and water-soluble vitamins. The fat-soluble vitamins are A, D, E, and K. The water-soluble vitamins are B and C. In general, fat-soluble vitamins are stored longer and have slower changes in levels, and require less frequent supplementation. Water-soluble vitamins are more quickly excreted in excess and require more frequent supplementation. Vitamin A Vitamin A is found in the diet as retinols or provitamin carotenoids, depending on the species and diet. Vitamin A is used in vision, the immune system, skin condition and is an antioxidant. Forage-based diets lose provitamin A during storage, meaning that the longer hay is stored, the lower the provitamin A levels will be. If adequate levels are not seen in the diet for an extended period, supplementation may be necessary. Vitamin A is generally given as an injection in conjunction with vitamins E and D.