NUTRITIONAL AND DEVELOPMENTAL ROLES OF INSULIN-LIKE GROWTH-FACTORS INPOULTRY

Insulin-like growth factor-I and -II are important multifunctional pol ypeptides that interact with membrane-bound receptors as well as solub le binding proteins. The biological actions of these hormones are mult ifaceted and dependent to a large extent on binding protein interactio ns. Some unique differences in insulin-like growth factor physiology a nd biochemistry are evident between mammalian and avian species. These include amino acid compositional and significant receptor differences as well as binding protein status. The biological response to both gr owth factors is different in birds. A greater proportion of the insuli n-like growth factors exists in plasma as free peptide compared with t he situation in mammals. This review is a brief summary of our knowled ge of insulin-like growth factor physiology in domestic fowl.