Managerial risk factors for intramammary coagulase-positive staphylococci in Ohio dairy herds

A stratified random sample of Ohio dairy herds was studied to relate herd management and environmental conditions to intramammary infection with coagulase-positive staphylococci. Management and environmental conditions were assessed by investigator observation and by interview with the diary producers. Separate analyses for each of 70 management and environmental independent variables identified many potential disease determinants. A logistic regression model used five model degrees of freedom to predict the prevalence of coagulase-positive staphylococci in more than 1% of quarters. Increased risk of infection with coagulase-positive staphylococci was associated with dirty udders, high-line milking systems, and less crowded housing conditions. Decreased risk of infection was associated with a herd size of 50-100 cows.