ANTIOXIDANT STATUS IN DAIRY COWS DURING LACTATION

Abstract

During the transition period important metabolic changes occur in dairy cows, which can also experience oxidative stress. The study was carried out to asses the activity of antioxidant enzymes, the level of lipid peroxidation ant the level of serum antioxidants, carotenoids and uric acid. SOD activity in cows was situated around 1365 U/g Hb in the first week after parturition, 1890 U/g Hb in the second week, 2290 c in the third week, 1896 U/g Hb in the fourth week, and 1905 U/g Hb in the sixth week after parturition, value close to that of the cows in late lactation (2005 U/g Hb). GPX activity in cows was situated around 129 U/g Hb in the first week after parturition, and than increased to reach 166 U/g Hb in the sixth week after parturition, value comparable with that of cows in late lactation (160 U/g Hb). The same pattern of enzyme activity modification was observed for blood catalase. The maximum level of lipid peroxidation was observed in the first week after parturition (62 µmols/l), comparing with the level of MDA in the cows in late lactation (35 µmol/l). In the second week after parturition the level of MDA decrease significantly, and remains at approximatively same values during the experiment. The high level of MDA in the first week after parturition correlates with a low activity of antioxidant enzymes (SOD, GPX, catalase) and a low level of antioxidants. The experimental data show that during parturition and onset of lactation oxidative stress appears in dairy cows, but these modifications are of short-therm.