Factors associated with bacteriological cure during lactation after therapy for subclinical mastitis caused by Staphylococcus aureus.

The objective of this study was to determine the factors that were associated with the cure of subclinical mastitis caused by Staphylococcus aureus treated during lactation. One hundred forty-three quarters that were infected with S. aureus were available from a number of treatment trials. Analysis of these data showed that the most important factors associated with cure were age of the cow, somatic cell count at the time of treatment, presence of the infection in the front quarters, and stage of lactation. Other factors, such as number of infected quarters per cow and sensitivity or resistance of the strain to penicillin, were not significant. Because of the relatively low probability of cure, it is important to know risk factors for cure and, hence, to choose cows for treatment with great care. Using these data, a prediction equation was developed to determine the cure rate of subclinical mastitis caused by S. aureus when treated during lactation.