A study on heifer mastitis in Japan and its causative microorganisms.

Survey and bacteriological examination were conducted on heifer mastitis in Hokkaido, the northern island of Japan over a period from 1976 to 1981. The disease occurred in heifers, mostly 13 to 18 months old, less than a half of which was pregnant in late summer or in August and September. Infection occurred predominantly in a front quarter than a rear one. Some microorganisms were isolated by the CO2 gas jet method from all the 74 secretions from the affected quarters of 67 heifers. Actinomyces pyogenes ( Corynebacterium pyogenes) was isolated from 49 secretions (66.2%), forty-six of which were involved in mixed infection with other microorganisms, including Peptococcus indolicus that was found in 41 secretions. Streptococcus dysgalactiae was isolated from 13 secretions, from nine of which were obtained pure cultures. The microorganisms harbored in secretion were much more closely associated simultaneously with A. pyogenes and P. indolicus than with A. pyogenes alone or a combination of A. pyogenes and any other microorganism than P. indolicus . This is the first report that P. indolicus was isolated from heifer mastitis in Japan. The "score" used for the expression of quality of milk secretion seemed to be useful for the clinical diagnosis of heifer mastitis. The disease in Hokkaido may be etiologically identical with summer mastitis found in the northern European countries.