Making Further Progress in Low Somatic Cell Count Herds

Somatic cell counts (SCC) serve as valuable indicators of prevalence of intramammary infection (IMI). A strong positive correlation between bulk tank SCC and prevalence of infection has been well established. However, herds with low prevalences of subclinical infection may yet have a mastitis problem, particularly that caused by organisms of environmental origin.These would include primarily streptococci other than agalactiae (nonag. strep.), and the lactose fermenting organisms of the family Enterobacteriaceae, loosely termed coliforms. This paper reviews the problems facing dairy farmers that have been able to maintain their herd SCC, and thus subclinical mastitis, at a low level. Means to assess the mastitis problem in such herds and mastitis control methods thought to be effective is discussed. With adequate mastitis control measures available to control Strep. agalactiae and Staph. aureus, future mastitis research should necessarily be directed to control of environmental organisms.