Vitamin H2 (Biotin)

Biotin is distributed widely in low concentrations in plant and animal tissues. It was first described as the factor protecting against egg white injury caused by avidin, a glycoprotein that binds biotin in the intestinal tract and thus inhibits biotin absorption. Biotin is slightly soluble in water. This vitamin has a bicyclic structure consisting of a ureido ring fused with a tetrahydrothiophine ring bearing a valeric acid side chain. Thus biotin plays an essential role in both carbohydrate and lipid metabolism and can also influence protein synthesis via its effects on the nature and rate of formation of ribonucleic acid.
Biotin deficiency results in dermatitis of the feet and the skin around the beak and eyes similar to that described for pantothenic acid deficiency. Perosis and footpad dermatitis are also characteristic signs. Embryos are also sensitive to biotin status. Congenital perosis, ataxia, and characteristic skeletal deformities may be seen in embryos and newly hatched chicks when hens are fed a deficient diet. Embryonic deformities include a shortened tibiotarsus that is bent posteriorly, a much shortened tarsometatarsus, shortening of the bones of the wing and skull, and shortening and bending of the anterior end of the scapula.