Activity of the antioxidative enzymes in milk during early postpartum of dairy cows

Abstract

Essential differences between intrauterine and extrauterine environment results in neonate exposition to oxidative stress condition. Antioxidants in milk can enhanced immune defense of calves by reducing oxidative damage which is crucial for it’s further development. Among the antioxidative enzymes, superoxid dismutase (SOD) and glutathion peroxidase (GPX) have important role in milk antioxidative capacity. The two years prospective study was carried out to assess the changes occurring in the milk activity of antioxidant enzymes SOD and GPX in two physiological periods: period from beginning of lactation until 21st day in lactation and period from 22nd to 42nd day in lactation. The cows were allocated in groups regarding the season of calving. Determination of the enzyme activity was assayed on milk serum by using spectrofotometric methods. The average test day milk yield of the dairy cows included in survey was ranged from 28.15±0.485 to 28.79±0.472 kg. The average activity of SOD in period from beginning of lactation until 21st day in lactation was 91.67±7.927 mU/mg proteins, than decreasing to 90,89±8,526 mU/mg proteins in the second physiological period from 22nd to 42nd day in lactation. The average activity of GPx in period from beginning of lactation until 21st day in lactation was 231.90±12.133 mU/mg proteins, than increasing in the period from 22nd to 42nd day in lactation (236.16±13.175 mU/mg proteins). Physiological stages in early lactation when milk samples were taken didn’t have statistical significant influence on SOD and GPx activity in milk serum. The activity of SOD and GPx in milk serum statisticlly significant (p<0.001) differed between season years of calving. The highest statistical significant difference in the activity of SOD in milk serum was found in the summer and fall seasons in second year of survey compared with other seasons. Regarding the GPx activity in milk serum there was statistical significant differences between all seasons of years. The test day milk yield had statistical significant influence on GPx activity in milk serum but this factor didn’t have statistical significant influence on SOD activity. There was statistically significant positive correlation between the activity of GPx and SOD in milk serum. The SOD/GPx ratio in milk has important role in the balance of reactive oxidative metabolites in milk.