Dogs and cats have a metabolic requirement for biotin, but a dietary requirement has not been established when foods from natural ingredients are fed. Requirements for biotin are difficult to establish due to biotin variability in feed content and bioavailability. Likewise, it is difficult to obtain a quantitative requirement for biotin as the vitamin is synthesized by many different microorganisms and certain fungi. These microorganisms are found in the lower part of the intestinal tract, a region in which absorption of nutrients is generally reduced. There is evidence in the pig, however, that intestinal microflora make a significant contribution to the body pool of available biotin (Barth et al., 1986). Kopinski (1989) has reported that this microbially synthesized biotin is of little benefit to the pig, however. What is not known for the various species is the extent of microbial synthesis or the biotin availability to the host.
It is concluded that microorganisms contribute to animal and human requirements, as the use of some sulfa drugs such as sulfathalidine can induce deficiency under some circumstances. Rate and extent of biotin synthesis may be dependent upon the level of other dietary components. In rats and poultry, it has been shown that polyunsaturated fatty acids (PUFA), ascorbic acid and other B vitamins may influence the demand for biotin. Addition of PUFA to fat-free, biotin-deficient diets increased severity of dermal lesions (Roland and Edwards, 1971). Biotin is rapidly destroyed as feeds become rancid. Pure biotin was inactivated to an extent of 96% in 12 hours when linoleic acid of a high peroxide number was added to the diet (Pavcek and Shull, 1942). In the presence of alpha-tocopherol, this destruction amounted to only 40% after 48 hours.
