As a coenzyme, biotin is of great importance for building up important enzyme systems. These enzymes are involved in fatty acid synthesis, gluconeogenesis, propionic acid metabolism, the degradation of the amino acid leucine and the building of DNA and RNA. Depending on the severity and duration of the deficiency, a biotin deficiency can cause damage to the skin, hair, claws and hooves, retarded growth, fertility problems and poor feathering of the poultry. Oil meals andbrewer's yeastcontain a lot of biotin, whereas cereals contain little of this vitamin. Depending on the animal's needs, the feed is specifically supplemented with biotin to ensure the supply. In contrast to pigs and poultry, rabbits and horses can cover a considerable part of their requirements through the biotin production of the large intestine bacteria.