Diagnostic evaluation of milk lactate dehydrogenase and alkaline phosphatase activities by receiver operating characteristic analysis curve in early lactation of ewes with subclinical mastitis

The aim of the present study was to investigate the diagnostic evaluation of milk lactate dehydrogenase (mLDH) and alkaline phosphatase (mALP) activities by receiver operating characteristic (ROC) analysis curve in early lactation of ewes with subclinical mastitis (SCM) and determine the correlation between number of somatic cell count (SCC) and mLDH and mALP activities. A total of 196 udder half milk samples were collected within the first 6 weeks of lambing. The SCM was determined by positive milk bacterial culture and positive California mastitis test (CMT); SCC was determined by fossomatic method and enzyme activities were determined spectrophotometrically. The mLDH and mALP of SCM cases were positively correlated with SCC values. Values of mLDH, mALP and SCC were significantly higher in SCM than non-SCM udder halves. The optimum cut-off points of mLDH and mALP activities for SCM diagnosis were determined at 203.61 (U L(-1)) and 329.84 (U L(-1)), respectively. In conclusion, SCC has positive correlation with mALP and mLDH activities in SCM ewes and mLDH and mALP activities could be considered as reliable indicators for intra-mammary inflammation diagnosis.