Currently, somatic cell count (SCC) and bacterial culture is considered as the gold standard of detecting subclinical mastitis. However, the above-mentioned tests have a low diagnostic accuracy. Therefore, for identification of infected animals, new biomarkers with high clinical accuracy are needed. The objective of this study was to determine the diagnostic value of milk lactate dehydrogenase (LDH) and alkaline phosphatase (ALP) for the diagnosis of subclinical mastitis in dairy cows. The activities of these enzymes increase during mastitis, which make them to be the potential biomarkers for screening of mastitis. A total of 145 clinically healthy cows were randomly selected. Of these, 77 cows were considered to be affected by subclinical mastitis based on a SCC higher than 100×1000 cells/ml of milk and positive bacterial culture results of milk samples obtained from at least one of the quarters. Enzymes activities were measured in blood serum and defatted milk (centrifuged at 5000 g for 15 min at 4Ã?¢Ã?â??Ã?Æ?) using commercial kits. Diagnostic sensitivity and specificity and cutoff points for each test were determined via receiver-operating characteristics curve. Significant (P<0.001) increases in the mean and median activities of LDH and ALP were found in the milk samples collected from cows with subclinical mastitis. Milk LDH had the most clinical accuracy with 94.8% sensitivity and 94.1% specificity at cutoff point of 109 U/L. The results of the present study showed that the measurement of LDH and ALP activities in milk samples could be used as reliable method for detection of bovine subclinical mastitis.
