Low frequency of antimicrobial use in nursing beef calves from Western Canada has limited association with antimicrobial resistance in fecal organisms.

OBJECTIVE

To examined potential risk factors for the frequency of antimicrobial use (AMU) within herd and potential associations between AMU and the frequency of antimicrobial resistance (AMR) in fecal organisms in beef calves.

METHODS

In this observational study, all interested herds from the Canadian Cow-Calf Surveillance Network shared individual treatment records in 2021 for nursing calves (N = 56); a subset also provided fecal samples from calves in the spring and fall of 2021 (N = 31). Herd attributes were examined for associations with frequency of AMU. Associations were also estimated between frequency of AMU by drug class and subsequent frequency of AMR for Escherichia coli and Enterococcus spp in the spring and fall.

RESULTS

Individual animal AMU for nursing calves included oxytetracycline, florfenicol, and macrolides. Herds with at least 300 versus < 300 cows, that sold some seedstock compared to 100% commercial, and assisted more cows at calving reported more frequent AMU within herd. Antimicrobial use drug class and AMR class were not associated with E coli or Enterococcus spp recovered from calf fecal samples in the spring or fall of 2021, except for macrolide use and macrolide resistance in the fall for Enterococcus spp (OR, 1.54; 95% CI, 1.26 to 1.89 per 10% increase).

CONCLUSIONS

The frequency of AMU in nursing calves is relatively low in most herds. Antimicrobial use was not associated with AMR, with 1 exception. The availability of individual records and fecal samples limited statistical power.

CLINICAL RELEVANCE

Antimicrobial stewardship, including best practices for prescribing and administering antimicrobials, remains a priority for veterinarians and the beef industry.