Investigators examined antimicrobial drug use practices and reason for treatment as part of a large on-farm observational study of cow–calf herds from western Canada. Reason for treatment and antimicrobial drug use (AMU) were described using data collected during the calving season (January 1 to June 30, 2002). The study included 28,573 calves and 36,634 cows and heifers from 203 beef herds. All herds had more than 50 cows. Individual animal treatment records and a herd-level standardized questionnaire were collected from every herd. During the period of January 1 to June 30, 2002 at least one treatment was reported in 14% (95% CI, 11–17) of calves and 2.7% (95% CI, 2.2–3.4) of cows and heifers from these herds. The median percent of calves reported as treated per farm was 6.5% (range 0–100%) while the median percent of cows and heifers reported as treated was 0.9% (range 0–15%). Antimicrobial drugs used during the calving season were primarily for disease treatment rather than prevention or growth promotion. Diarrhea was the primary reason for treating calves and metritis was the primary reason for treating cows. Parenteral antimicrobial drugs were the most common formulation used in both calves and cows. The most commonly used antimicrobial drugs in these herds were tetracyclines, sulphonamides, and florfenicol. This study provides baseline estimates of the frequency of antimicrobial drug exposure, the types of drugs used, and diseases treated in these cow–calf herds. The challenges identified in collecting these data can be used to improve the design of future on-farm studies.
