Biotin is important for normal function of the thyroid and adrenal glands, the reproductive tract and the nervous system. Its effect on the cutaneous system is most dramatic, since a severe dermatitis is the major obvious clinical sign of biotin deficiency in animals, including dogs and cats.
Biotin deficiency results in reduced growth rate and impaired feed conversion and produces a wide variety of clinical signs, particularly dermal lesions. There is a hyperkeratosis of the superficial and follicular epithelia, giving the animal a scruffy appearance due to exfoliation of the skin. These lesions begin on the limbs and face and spread over the body. Apparently biotin deficiency in dogs and cats has occurred only when animals have been fed a biotin antagonist (e.g., avidin) and/or have been treated with antibiotics.
Detection of biotin deficiency in various species includes decrease in urine and plasma biotin and reduced activity of carboxylase enzymes. Feeding raw egg white significantly reduced urinary biotin and the activity of various biotin-dependent enzymes (pyruvate and propionyl CoA carboxylases) in the liver and kidneys of dogs (Shen et al., 1977). Biotin-deficient cats had a decrease in the activity of liver propionyl CoA carboxylase (Carey and Morris, 1977).
