This document discusses vitamins, their sources and supplementation. Vitamins are organic compounds required in trace amounts for normal growth and function as coenzymes in metabolic processes. Vitamin levels vary in sources and they are generally destroyed by heat, light, oxidation and mold growth. Vitamins are classified as either water-soluble like B vitamins and vitamin C which are not stored in the body, or fat-soluble like vitamins A, D, E and K which may be stored. The sources and stability of different vitamins like A, D, E and K are described. General rules of vitamin supplementation are that they are usually limiting in natural diets and supplementation is inexpensive, especially for animals under stress.