A STUDY OF MASTITIS BACTERIA AND HERD MANAGEMENT-PRACTICES TO IDENTIFY THEIR RELATIONSHIP TO HIGH SOMATIC-CELL COUNTS IN BULK TANK MILK

Thirty dairy herds, selected to cover a wide range of bulk tank somati c cell count (BTSCC) values, were used to study the relationship betwe en the levels of the principal species of mastitis-causing bacteria, h erd management practices and the BTSCC. A good, correlation was found between the number of mastitis streptococci (Streptococcus agalactiae, S. dysgalactiae and S. uberis) found in bulk tank milk and the BTSCC. Staphylococcus aureus was less significantly correlated to BTSCC, but was of increasing importance in borderline BTSCC herds, where lower e xcretion levels into milk were unlikely to trigger hygiene penalties a nd so alert producers to the presence of a significant mastitis proble m. High BTSCC herds had significantly lower yields and were less likel y to use a post-milking teat dip or to have a regular programme of mil king machine maintenance or automatic cluster removal. These herds als o tended to buy in replacements rather than breed their own. Overall t he management of high BTSCC herds showed less commitment to implementi ng mastitis control procedures than herds with a consistently low BTSC C.