Diagnostic Value of Milk Total Antioxidant Status (TAS) and Malondialdehyde (MDA) in Cows with Subclinical Mastitis

The sensitivity and specificity of milk somatic cell count (SCC) and bacterial culture as the golden standards for the diagnosis of bovine subclinical mastitis are low. Mastitis leads to the increased formation of free radicals, elevated oxidative and nitrosative stresses, and decreased antioxidant activity in milk. Therefore, the aim of this study was to determine the diagnostic value of milk malondialdehyde (MDA) and total antioxidant status (TAS) for the diagnosis of subclinical mastitis in dairy cows. A total of 90 clinically healthy Holstein cows were randomly selected from dairy farms of Tehran province, Iran. Next, 55 of these cows were diagnosed to have subclinical mastitis based on an SCC of higher than 130×1000 cells/mL of obtained milk samples. Milk MDA level was determined by the thiobarbituric acid method and TAS was measured using a commercial kit (Randox Laboratories, England). The diagnostic sensitivity, specificity, and cut-off points for the tests were determined by the receiver operating characteristic analysis. Our findings revealed that the mean and median of milk MDA and TAS were significantly higher and lower in the milk samples collected from cows with subclinical mastitis, compared to the healthy subjects. Moreover, milk MDA level was found to have the highest clinical accuracy at the cut-off points of 44.5nmol/ml. The results showed that the sensitivity and specificity of this biomarker in milk for subclinical mastitis diagnosis was both 100%. According to the results of this study, MDA can be considered as potential reliable substitutes for SCC in the diagnosis of bovine subclinical mastitis.