SENSITIVITY AND SPECIFICITY OF CALIFORNIA MASTITIS TEST (CMT) AND COW MILK ELECTRICAL CONDUCTIVITY THROUGHOUT LACTATION.

Mastitis is the most prevalent infectious disease of dairy herds. Subclinical form has great importance in reducing yield and milk quality. Physical examination of udder or milk cannot detect disease process, and a diagnostic test is required. Early detection of infection reduces transmission. Researches are made to determine the influence of environmental and physiological factors. During one year 1,584 samples from clinically health quarters were taken to evaluate sensitivity and specificity of CMT and MEC in detecting subclinical mastitis throughout lactation. Microbiological tests were used as the gold standard. Prevalence was 14.52%. CMT showed the highest sensitivity(100%) and MEC the highest specificity (86.98%). CMT decreased its specificity (from 8.96% to 0.40%) from early to late lactation. MEC sensitivity was increased (from 5.71% to 21.43%) from early to late lactation, but specificity (86.98%)increased only in mid lactation. A simulation, using Win Episcope 2.0, demonstrated that if CMT and MEC were used as serial tests, specificity would increase to 85.05% in early lactation and to 77.82% in late lactation. In mid lactation, an increase in sensitivity (98.21%) would occur if they were used as parallel tests, whereas specificity would increase to 87.28% if they were used as serial tests. Results suggest that physiological changes occurring in early and late lactation may interfere with CMT and MEC results. This problem can be minimized using both tests so the results can be more reliable and better used to take decisions. KEY-WORDS: Mastitis. CMT. Milk Electrical Conductivity. Sensitivity. Specificity.