Antioxidant status in dairy cows during transition period

Abstract

During the transition period important metabolic changes occur in dairy cows, which can also experience oxidative stress. The two years prospective study was carried out to assess the changes occurring in the activity of antioxidant enzymes superoxid dismutase (SOD) and glutathion peroxidase (GPX) in three physiological periods: dry period 21 days before calving, period from beginning of lactation until 21st day in lactation, and period from 22nd to 42nd day in lactation. Determination of the enzyme activity was assayed on blood serum by using spectrofotometric methods. The average activity of SOD in period before calving was 24.20±2.319 mU/mg proteins, reaching the value of 43.94±3.864 mU/mg proteins in the second period and in the third period from 22nd to 42nd day in lactation, the activity was 26.77±2.201 mU/mg proteins. The average activity of GPx in period before calving was 251.79±9.363 mU/mg proteins, than increasing in period from beginning of lactation until 21st day in lactation (372.45±17.533 mU/mg proteins) and in the third period from 22nd to 42nd day in lactation, the activity was 319.40±14.307 mU/mg proteins. Physiological stages in transition period when blood samples was taken, showed statistical significant influence (p<0.001) on SOD and GPx activity in blood serum. Significant difference in the activity of SOD in blood serum was found in period before calving as compared to period from calving to 21st day in lactation, and also in period from calving to 21st day in lactation as compared to period from 22nd to 42nd day in lactation. Significant differences in the activity of GPx in blood serum was found between all three physiological periods, but biggest significant difference in activity was found in period before calving as compared to periods in lactation. There were statistically significant positive correlations between the activity of GPx and SOD in blood serum. Dairy cows experience oxidative stress in transition period from gestation to lactation.