The role of vitamin E for the functionality of the immune system has been extensively studied by several research groups and is based on the capability of vitamin E to prevent lipid peroxide-tion in membranes caused by lipid peroxyl radicals. Infectious diseases are an important factor in the production of free radicals for example as a consequence of macrophage function. Dietary levels of vitamin E ≥ 60 mg/kg were found necessary to attain maximum sow immunologic and reproductive health responses.