[Changes of reduction-oxidation balance in pregnant ruminants]

By-products of oxygen metabolism are the element's reactive species and their derivaties. Reactive oxygen species (ROS) and particularly free oxygen radicals (FOR) are characterized by high chemical activity. They can easily react with cell macromolecules (lipids, protein and DNA), leading to change of their structure and function and finally to the cell death and tissue damage. In defense against ROS, organism formed an antioxidative system of several stages with many completing each other reciprocally. The system is made by enzymatic antioxidants, nonenzymatic proteins binding ions of transition metals, and low molecular antioxidants. Oxidative stress is a consequence of disorder between ROS generation and efficiency of the antioxidant system. Pregnancy is a physiological state characterized by increased ROS generation especially in the last trimester of the gestation and at the beginning of lactation. In this paper we have presented changes in total antioxidant status (TAS) of plasma and its chosen components in domestic milking ruminants in transition period. Literature data prove explicitly that during late pregnancy and early lactation period, functional burden of balance control mechanism pro/antioxidants increases significantly.