| Summary: | The notion “endotoxin” is conditional, for any normal metabolit has a toxic impact if it has an excessive accumulation in an organism. Endotoxins include products of breakdown of tissue proteins, peroxides and other products of free radical oxidation, low molecular weight toxins, toxins of microorganisms. Current knowledge on the mechanism of endotoxin action on the organism of pregnant cows is based on the key role of the immune system: it provides animals with protection against infections, eliminates extraneous elements of endogenous and exogenous origin. It is understood that under endogenous intoxication, toxic metabolites suppress the activity of an organism’s immune system and decreases the resistance of an organism to negative effects of environmental factors. Animals under endogenous intoxication had the following clinical symptoms: swelling of mammary gland, edemas of external genitals, anemia of mucous membranes, functional disorders of proventriculuses and intestines, and the animals were stressed. It was found that under endogenous intoxication at 8–9 months of pregnancy, the blood of highly-productive cows had a tendency of decrease in the number of erythrocytes by 21.0% and decrease in the level of hemoglobin by 24.3%, and increase in the number of leucocytes by 7.6% compared to the value for the blood of cows with physiological pregnancy process. The development of endogenous intoxication among pregnant cows causes disorders in protein-synthesizing function of liver, which is indicated by decrease in the level of total protein and its fractions. We found that endogenous intoxication decreased the content of total protein in the blood by 18.4%. Over the period of study, among pregnant cows under the development of endogenous intoxication, heightened activity of amino transferases in the blood was observed. In the ninth month of pregnancy, the activity of amino transferases in blood serum of cows from the experimental group increased by 28.6%, and the activity of aspartate aminotransferase increased by 20.1% respectively. Increase in the activity of amino transferases and decrease in the level of total protein and its fractions in the blood serum is one of the first biochemical tests for the diagnosis of endotoxin manifestations and indicates destructive processes in the liver. We found that pregnant cows under the development of endogenous intoxication suffered disorders in detoxicating function of the liver and disorders in filtrating function of the kidneys. The developing endogenous intoxication of pregnant cows suppressed the activity of enzymes in their glutathione system of antioxidant protection, which is indicated by decrease in the activity of glutathione peroxidase by 27.5%, glutathione reductase by 42.9%, glucose-6-phosphate dehydrogenase by 11.2% in the blood serum. The lowest activity of enzymes of glutathione system in the blood of highly-productive cows under endogenous intoxication was observed in their ninth month of pregnancy, which is related to increase in activation of processes of lipid peroxidation and imbalance between the activity of antioxidant system and intensity of lipid peroxidation. A significant increase in the content of lipid hydroperoxides by 70.9% and in concentration of malondialdehide by 54.8% was observed. Imbalance in generation of active forms of oxygen and their metabolites, exhaustion of antioxidant system and disorders in its balance cause oxidative stress.
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