Object of research – antioxidant defense system of mixed bacteria and infusoria population of the cattle rumen content, influence of vitamin E on it’s activity, some modulators, macro and microelemrnts in vitro. Purpose – The goal of the dissertation was to study the antioxidant defense system condition (antioxidant enzymes activity level; lipid peroxidation products, obtained from the 6-month age calves rumen content, in bacteria and infusoria activity level; influence of vitamin E, selenium, some modulators, macro- and microelements additions into their incubation environment. Methods of – microbiology, biochemistry, physics-chemistry, statistic. Novelty – The high content of lipid peroxidation products and significant activity of their antioxidant defense system (superoxidedismutase, catalase, glutathioneperoxi-dase, glutathionereductase) in the cells of mixed population of cattle rumen bacteria and infusoria was established for the first time. The inhibiting influence on the lipid peroxidation andstimulating effect on the antioxidant system activity in bacteria and infusoria cells at vitamin E and selenium addition into the incubation environment was established. It was also proved that adding S(II), Cr(III), Zn(II), Ni(II), Fe(III) and Mn(II) into the incubation environment had inhibiting influence and adding S(VI) and Cr(VI) — stimulating influence on lipid peroxidation in bacteria cells. At adding the above-mentioned mineral elements into the incubation environment the lipid peroxidation products changes in infusoria cells were weaker than in bacteria. Superoxidedismute activity probably increased in bacteria and infusoria cells at adding S(VI) and Cr(VI) and also Zn, Ni, Fe, Mn salts into the incubation environment. Adding Cr(III), Zn and Mn salts into the incubation environment caused the increase of catalase activity. Adding S(II) caused the decrease of the activity of this enzyme in bacteria and infusoria cells. Addition of S(II), Zn and Fe increases glutathioneperoxidase activity in bacteria cells and S(VI), Zn, Ni, Mn — in infusoria cells. The catalase was revealed and purified in mixed fraction of rumen microorganisms. The activating influence of the Zn substrate, Ni, Fe, Cr additions on this enzyme activity was established. Also the inhibiting influence of cadmium, selenium, cysteine and sodium azid was established.
