Micronutrients are as important as major nutrients for the animal body. Vitamins are organic compounds required in minute amounts to assist metabolic processes and formation of tissue structure. It must be understood that they neither furnish energy to the body nor do they form part of tissue structure. Vitamins are classified into fat soluble and water soluble. Though they were named initially based on their solubility as fat soluble A fractions and water soluble B fractions, presently the chemical structure and their metabolic functions are well understood. While fat soluble vitamins can be stored in the body in fat reserves, the water soluble vitamins are required to be supplied daily, as they cannot be stored in the body.
The animal body contains about 50 mineral elements all of which are not exactly required for the animal system. Certain major elements and some trace elements are known to be essential and required to be present in the diet. Major elements include elements are iron, copper, cobalt, manganese, iodine, selenium, molybdenum, and zinc. It is presently recognized that elements like chromium, fluorine, nickel and vanadium may also play a role in animal nutrition, though detailed evidences are yet to be established. Many elements are accidentally present in the animal body with out any known functions. Deficiency of essential elements causes specific deficiency disorders and excess intake may cause toxicity symptoms. Functions of minerals may be classified into protective, structural, regulatory and general metabolic functions.