ETIOLOGY AND PREVALENCE OF SUBCLINICAL MASTITIS IN THE MANCHEGA SHEEPAT MID-LATE LACTATION

Prevalence of subclinical mastitis in 466 Manchega sheep was determine d at 3 and 4 mo of lactation. A high proportion of glands and ewes (26 .8% and 36.7%, respectively) showed bacterial infection, which was att ributable to Staphylococcus in 83.2% of cases. Within this genus, Stap hylococcus epidermidis reached 66.8%. Among the indirect diagnostic me thods, somatic cell count (SCC) was the best predictor of mastitis inf ection, with a threshold value of 2.5 x 10(5) cells/ml of milk corresp onding to a specificity of 89.4% and sensitivity of 91.0%. Prevalence of subclinical mastitis was higher in sheep with high milk production (P < 0.001). There was a great diversity in milk production, percentag es of milk protein, fat or SNF within each farm and, with this diversi ty, significant differences between healthy and subclinical mastitis-a ffected animals could not be detected for such parameters. Seroprevale nce of Maedi Visna virus in this study was 12%. A mastitis control pro gram is recommended for Manchega sheep.