EC and CMT detect subclinical mastitis in dairy sheep but less sensitive than in dairy cows

Reliable tests to monitor the udder health of ewes are necessary to ensure a high raw milk quality in organic dairy sheep farms. 328 udder halves of 164 ewes from six organic farms were sampled in 2005. Foremilk samples were used to measure the electrical conductivity (EC) of the milk and for California Mastitis Test (CMT). Afterwards samples for cyto-bacteriological examination were aseptically collected. Pathogens were detected in 31 samples. In 24 cases coagulase-negative staphylococci caused the infection. Half udder samples free from pathogens contained 61.000 cells ml(-1) on average. According to the recommendations of the German Veterinary Association (DVG, 2002) for the evaluation of cytobacteriological results of cow milk samples, 73.0 % of the halves were healthy and 5.3 % had a subdinical mastitis. CMT values corresponded with the measured somatic cell count (r = 0.53, p < 0.01) and the mean EC difference between healthy and udder halves with subdinical mastitis was 0.4 mS cm(-1), nearly similar to the well known threshold for mastitis detection in cows. Besides the bacteriological analysis we recommend to use 100,000 cells ml(-1) as a threshold to discriminate between healthy and mastitic halves and we have to say the common cow side tests are not so sensitive when applied to sheep milk.