Clinical symptoms of biotin deficiency in animals1

The main biochemical function of biotin, one of the B complex group of vitamins, is as a coenzyme in certain enzymatic reactions associated with decarboxylation and carbon dioxide fixation. It thus has an important role in intermediary metabolism (1). Biotin is so widely distributed in foods and so abundantly produced by intestinal bacteria that it is doubtful whether a spontaneous biotin deficiency ever occurs in the adult animal unless a biotin antagonist is present in the diet. The only antagonist likely to be of importance in human nutrition is avidin, a protein constituent of egg white. Avidin, if present in the diet, combines with biotin in the alimentary tract, thus rendering the vitamin unavailable. The avidin may be denatured and inactivated by prolonged heating of the egg white, although spray drying or heating at 40 C for 3 hr does not completely destroy its biotinbinding properties. The normal method of producing a biotin deficiency in human and animal studies is by feeding raw egg white. However, care should be exercised in interpreting such experiments, because reports have indicated that diets containing high levels of raw egg white or lower levels in combination with rancid oils can produce toxic effects which although similar to are not those of a biotin deficiency (2, 3). In humans, possibly the only symptom of a spontaneous biotin deficiency is the seborrheic dermatitis sometimes observed in very