Evaluation of the use of an on-farm system for bacteriologic culture of milk from cows with low-grade mastitis

Abstract

To determine factors associated with implementation and use of an on-farm system for bacteriologic culture of milk from cows with lowgrade mastitis, including information on how producers used the on-farm bacteriologic culture system to guide antimicrobial selection practices and the resulting impact on patterns of antimicrobial use. Retrospective cohort study. Producers of 81 dairy farms. Farms that used an on-farm system for bacteriologic culture of milk from January 2001 to July 2003 were surveyed. Over half of those producers continuing to use the on-farm culture delayed antimicrobial treatment pending results of bacteriologic culture. Most other producers initiated empirical antimicrobial treatment while bacteriologic culture results were pending. Several barriers to the use of an on-farm system were identified. Significant reductions in rates of antimicrobial use were detected when comparing antimicrobial use rates before and during use of the on-farm system. Most producers chose to treat cows with mastitis caused by gram-positive pathogens with antimicrobials, whereas treatment choices for cows with mastitis caused by gram-negative bacteria and in cases in which no growth was detected varied. Readily available results permit antimicrobial selections to be made on the basis of the causative agent of mastitis. Adoption of an on-farm system for bacteriologic culture of milk may result in significant reductions in the percentage of cows treated with antimicrobials. Decreasing antimicrobial use may have several benefits including preventing unnecessary discarding of milk, decreasing the potential for drug residues in milk, and improving treatment outcomes as a result of targeted treatments.