Determination of the diagnostic value of positive andnegative acute phase proteins of the milk as new andreliable biomarkers in bovine subclinical mastitis

Currently, somatic cell count (SCC) and bacterial culture is considered as the golden and ultimate standard methods for diagnosis of bovine subclinical mastitis. However, SCC has a low diagnostic accuracy. Therefore, foridentifcation of infected animals new biomarkers with high diagnostic accuracy are needed. Acute phase proteins(APPs) are proteins that are increased (positive APPs) or decreased (negative APPs) in response to inflammation.The objective of this study was to determine the diagnostic value of the milk APPs for the diagnosis of subclinicalmastitis in dairy cows. A total of 90 clinically healthy cows were randomly selected. Of these, 52 cows were considered to have subclinical mastitis based on a SCC higher than 130 × 1000 cells/mL of milk and positive bacterialculture results of milk samples obtained from at least one of the quarters. Milk amyloid A (MAA) concentrationwas measured using a commercial ELISA kit and albumin, α-lactalbumin, β-lactoglobulin, and immunoglobulin(Ig) were measured in whey samples by using cellulose acetate electrophoresis. Diagnostic sensitivity and specifcity and cutoff points for each test were determined via receiver-operating characteristics (ROC) analysis. Signifcant (P < 0.001) increases in the mean and median concentration of MAA, albumin, α-lactalbumin, and Ig werefound in the milk samples collected from cows with subclinical mastitis. MAA was the most accurate test witha diagnostic sensitivity of 92.3% and specifcity of 92.1% at cutoff point of > 1.6 mg/L. The results of this studyshowed that determination of MAA and some milk serum proteins such as albumin and immunoglobulins can beused as potential and reliable biomarkers for the diagnosis of bovine subclinical mastitis.