Paul et al. (1973) reported that an acute dose of biotin at the level of 5 mg per 100 g (5 mg per 6.25 oz) of body weight caused irregularities of the estrus cycle with heavy infiltration of leukocytes in the vagina of the rat up to 14 days after treatment. In additional rat studies, a dose of biotin at least 5,000 or 10,000 times the daily requirement had no deleterious effects (Mittelholzer, 1976). Studies with poultry and swine indicate that those species can safely tolerate dietary levels four to 10 times their nutritional requirements of biotin (NRC, 1987). In view of the poor retention of biotin for most species, higher levels may be tolerated. There is a lack of data available to estimate dietary tolerance levels of biotin for dogs and cats.
