ENZIMATIC ANTIOXIDANTS IN RAW COW MILK

Abstract

Dairy cows’ experience a drastic change in metabolism after parturition that can lead to oxidative stress. Lipid auto-oxidation in milk is affected by a complex interplay of prooxidants and antioxidants. Several of these compounds are also important nutrients in the human diet and may have other physiological effects. Among the others, 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. Totally, there were followed 211 cows allocated in groups regarding the season of calving. Determination of the enzyme activity was assayed on milk serum by using spectrofotometric methods. 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. The activity of SOD and GPx in milk statisticlly significant (p<0.001) differed between season years of calving. The highest statistical significant difference in the activity of SOD in milk was found in the summer and fall seasons in second year of survey compared with other seasons. Regarding the GPx activity in milk there was statistical significant differences between all seasons of years. The test day milk yield had statistical significant influence on GPx activity in milk 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 the milk samples. The SOD/GPx ratio in milk has important role in the balance of reactive oxidative metabolites in milk.