Use of somatic cell counts and California Mastitis Test results from udder halves milk samples to detect subclinical intramammary infection in Awassi sheep

A total of 1210 sheep milk samples were collected and examined. In 719 (59.4%) of these samples, bacterial culture did not yield any growth. Ninety-one percent (654/719) and 80% (570/719) of these samples had a somatic cell count of less than 1 × 106 cells/ml and a California Mastitis Test (CMT) score of ≤2+. All samples which yielded bacterial isolates, were considered to be infected. Of the infected samples, only 9% (44/493) had somatic cell counts (SCC) less than 1 × 106 cells/ml and none had a CMT score of <3+. Results of the unadjusted and adjusted (for stages of lactation) sensitivity, specificity, positive and negative predicted values of SCC on different thresholds and CMT were calculated.