Effects of lipoperoxidation and mitochondrial state on milk yield of dairy cows under technological stress

Evaluation of the physiological state of cattle is crucial in creating healthy, high-performing dairy cattle herds. Technological stress is one of the most critical factors determining the biological potential of higher-yielding cows. This work aimed to assess the effect of technological stress on various oxidative parameters and mitochondrial states in dairy cows' blood, milk yield and milk composition. The study was conducted on the black-and-white breed of healthy herds. Regrouping, changing service personnel, and carrying out veterinary and sanitary manipulations were considered technological stress factors. The concentration of cortisol in the blood serum was studied by the immunological method. The concentrations of malonic dialdehyde (MDA), diene conjugates (D.C.), Schiff bases (S.B.), reduced glutathione and catalase activity were measured spectrophotometrically. The mitochondrial state was estimated by laser interference microscopy. While the milk yield, protein and lipid composition of cow milk were studied using an ultrasound analyzer. The researched indicators were analyzed before and for 30 days after the effect of technological stress. Results of the study suggested that technological stress caused an increase in oxidative processes, along with a reduction of antioxidant activity of blood and milk at the initial stages of registration (1-7 days). The concentration of glutathione remained reduced for 30 days after technological stress. A decrease in mitochondrial refractoriness and disintegration accompanied these processes. The milk yield indicator decreased was not restored to the values of intact animals by 30 days after technological stress. Further, the protein and lipid composition also reduced. Thus, a decrease in the quantity and quality of milk under technological stress may be mediated by the development of oxidative stress, which the refractoriness and disintegration of mitochondria might trigger.