Two Cases of Bovine Mastitis Caused by Mycoplasma bovis

During the period from February to June, 1989, an attempt was made to isolate mycoplasmas from milk samples from cows with clinical mastitis which were negativein bacterial cultivation. Mycoplasma bovis (M.bovis) was isolated from 2 of 74 milk samples. A modified CMT (PLT) was performed with milk samples from cows on T-Farm where M.bovis mastitis occurred. Then isolation of mycoplasma was attempted with milk samples positive for PLT. As a result, M.bovis was purely isolated from 1 of 13 milk samples. In two cases in which M.bovis was isolated, the clinical signs were comparatively slight.They were not affected with clinically apparent pneumonia or arthritis. The time of occurrence of these mastitis coincided with an increase in the number of cows with mastitic and somatic cell counts of bulk milk on T-Farm in 1988.