ENVIRONMENTAL AND MANAGERIAL RISK-FACTORS OF INTRAMAMMARY INFECTION WITH COAGULASE-NEGATIVE STAPHYLOCOCCI IN OHIO DAIRY HERDS

A stratified random sample of Ohio dairy herds was studied to relate herd management and environmental conditions to the prevalence of intramammary infection with coagulase-negative staphylococci. Management and environmental conditions were assessed by investigator observation and by interview with the dairy producers. Separate analyses for each of 70 management and environmental independent variables identified many potential disease determinants. Analysis of covariance models were developed to predict the prevalence of coagulase-negative staphylococci. The first model used seven model degrees of freedom, had an R-squared of 0.62, and included the following independent variables: use of a cloth for washing cows, use of a hypochlorite- or iodine-based post-milking teat dip, a population of milking cows less than 50, the amount of bedding provided, use of free stall housing, an interaction between a small herd size and the amount of bedding provided and an interaction between the use of free stalls and the type of post-milking teat dip. The second model had an R-squared of 0.54 and was reduced to five model degrees of freedom by exclusion of the variables for use of free stalls and the interaction between free stalls and type of post-milking teat dip.