SENSITIVITY AND SPECIFICITY ANALYSIS FOR SOMATIC-CELL COUNT (SCC) USED TO PREDICT BACTERIOLOGICALLY POSITIVE SUBCLINICAL MASTITIS AT CALVING IN A DAIRY-HERD WITH LOW SCC

Objective-Validate, by sensitivity and specificity analyses, use of so matic cell count (SCC) to predict bacteriologically positive subclinic al mastitis in a California dairy herd with low SCC. Design-Study of m onthly dairy herd improvement SCC obtained from the immediate precedin g lactation and individual cow composite milk sample microbiologic iso lates collected at carving. Animals-515 California dairy cows with SCC and culture data. Procedure-Somatic cell count sensitivity and specif icity analyses with combinations of SCC parameter and at various thres holds were done, using the bacterial isolates as the standard. Results -Combination of SCC threshold and SCC parameters could not be develope d that had sufficient sensitivity and specificity to be a useful predi ctor of cows that would carve with subclinical mastitis. Clinical Impl ication-Under the conditions at this particular dairy, SCC could not b e used as a basis of prediction of cows that would calve with bacterio logically positive subclinical mastitis or require selective nonlactat ing-cow antibiotic treatment.