We investigated the changes in the plasma concentrations of oxidative stress markers in periparturient dairy cows in hot conditions. This study was performed on 10 cows from day -5 to day 10 after parturition. The experimental duration was divided into three periods: period 1 (5 days before parturition); period 2 (5 days after parturition); and period 3 (from day 6 to day 10 after parturition). The average rectal temperature in the cows during the experimental period was more than 39°C. Plasma aspartate aminotransferase activities in periods 2 and 3 were higher than that in period 1 (P<0.05). Blood urea nitrogen concentration in period 3 was lower than those in periods 1 and 2 (P<0.05). The total ascorbic acid concentration in the plasma in period 2 was greater than those in periods 1 and 3 (P<0.05). Thiobarbituric acid reactive substances (TBARS) concentrations in periods 2 and 3 were greater than that in period 1 (P<0.05). TBARS concentration was positively correlated with aspartate aminotransferase activity (P<0.05). These results suggested that oxidative stress increased in cows after parturition under hot climatic conditions.
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