Metrics and Monitoring of Antimicrobial Use in Dairy Production in Argentina

To address the rising threat of antimicrobial resistance, many countries are making efforts to establish baseline data and monitor antimicrobial use (AMU) in livestock. Although international reporting uses the total mass of antimicrobial agents standardized by animal biomass, other metrics may be more useful for individual countries, farmers or veterinarians to monitor progress over time. Using garbage can audits, we collected observational data on on-farm AMU from a convenience sample of 29 Argentinian dairy farms, separated into adult and youngstock groups, and calculated mass- and course-based metrics to benchmark estimated usage over the first 365 d of collection. Aggregated data from all farms gave an overall average (mean) usage of 25.8 mg/PCU; when calculated per farm, median AMU was 19.37 mg/PCU (range 4.97 to 58.90 mg/PCU). The third-generation cephalosporin, ceftiofur, was widely used as an injectable in adult cattle, while enrofloxacin was commonly used in youngstock. Oral ciprofloxacin - marketed as part of a multivitamin preparation for use in newborn calves - while only found on 4 farms, constituted 34% of all Category B antimicrobials, recommended as restricted for use in livestock by the European Medicines Agency. Course-based metrics demonstrated that high medicine usage on individual farms tended to occur in only one of the following categories: Category B medicines, youngstock, intramammary or systemic treatment in adults. These granular metrics help identify problem areas for individual farms, but may be less useful for formulating policy and measuring progress. A reduction in Category B usage appears to be a good opportunity for improved stewardship for the majority of participants and potentially for similar intensifying farms in the Argentinian dairy sector, although country-specific data (such as actual course doses and lengths used in the country) would improve calculation methodology for national monitoring.