Frequency of subclinical mastitis and observations on somatic cell counts in ewes' milk in northern Greece

Somatic cell counting by the Coulter Counter method, California mastitis test and bacteriological examination were performed on milk samples taken at fortnightly intervals throughout lactation from healthy primiparous and iniiltiparous ewes of the Chios and Karagouniki breeds and from healthy ewes in five grazing flocks in northern Greece.The proportion of the bacteriologically positive milk samples was 0·22. The prevalence of subclinical mastitis ranged, between the flocks, from 29 to 43% of the ewes. Subclinical mastitis occurred more frequently in Karagouniki than in Chios eives and in multiparous than in primiparous ewes of both breeds. Coagulase-negative staphylococci and S. aureus were isolated in 44 and 33% of the bacteriologically postive samples, respectively. No parity, breed or flock differences in normal somatic cell count were noticed, but stage of lactation influenced normal somatic cell count both in primiparous and multiparous ewes. The results of this investigation also suggest that (a) ovine milk samples with somatic cell count more than 1000 × 103 cells per ml, should be tested bacteriologically, (b) somatic cell count values between 1000 and 2000 × 103 cells per ml should cause suspicion about the presence of coagulase-negative staphylococci in the milk, and (c) the presence of S. aureus in ewe's milk results in a significant increase in somatic cell count, but the wide range of the values does not permit us to suggest any threshold value. The significant correlation between the results of the Coulter Counter somatic cell count method and the Califortiia mastitis test, indicates that the latter can be used for the determination of somatic cell count in ewe's milk.