Lomonosova, Voronezh, 394087 Russia, е-mail vnivipat@mail.ru, retsky@mail.ru Received March 19, 2014 Abstract Free radical lipid oxidation is currently considered as one of the dominant metabolic processes of physiological system functional activity. <...> When it goes beyond regulated limits it is considered as an inductor of free radical pathology oxidative stress. <...> In the conditions of a big dairy cattle breeding farm (Voronezh Province), specialized in Red-and-White breed, the functioning peculiarities of the peroxidation system lipid-oxidant defense in cows at the normal course of gestation and at gestosis, at the normal course of postpartum period and at puerperal endometritis, uterus subinvolution and ovarian dysfunction were studied. <...> The state of lipid peroxidation processes and antioxidant system were evaluated by determining total lipid content, cholesterol, triglycerides, malonic dialdehyde (MDA), nitrogen oxides (NO• ), E and C vitamins concentrations, glutathione peroxidase (GPO), glutathione reductase (GR), catalase, superoxide dismustase (SOD) activity in blood. <...> It is demonstrated that the high activity of lipid peroxidation reactions and the system of nitrogen oxide at decrease of antioxidant defense non-enzymic link capacity is the basis of gestosis and acute postnatal complications. <...> At mild gestosis the glutathione peroxidase activity, catalase activity and vitamin C concentration increased by 11.0 %, 14.3 %, 38.0 %, and 24.1 %, respectively, while vitamin Е concentration decreased by 11.7 % due to more consumption for neutralization of the toxic peroxidation products. <...> At more sever pathology, the glutathione peroxidase activity and catalase activity in blood increased by 26.0 % and 17.3 %, respectively, when compared to the healthy animals, while vitamins E and C concentrations decreased by 33.3 % (р < 0,01) and 17.2 %, respectively. <...> As free radical oxidation intensified, an anaerobic degradation of carbohydrates was activated to supply the tissues of developing fetus with energy under oxygen deficit occurred because of violation of the blood circulation. <...> Postpartum inflammation in the genital organs in cows developed against the background of increase of MDA concentration by 76.0 %, GPO and GR activity by 65.8 % and 14.6 %, respectively, SOD by 46.0 %, catalase by 45.7 %, 2.9 times increase of NO• concentration and reduction of vitamin E content by 35.5 %. <...> Infertile animals with ovarian dysfunction were characterized by high activity of lipid peroxidation <...>