What is the Risk of Antibiotic Resistance in Weaned Calves?

Project Title

Respiratory Pathogens in Calves at Weaning: A Pilot Sentinel Surveillance Project Evaluating AMR Risk for Calves Prior to Feedlot Entry


Cheryl Waldner cheryl.waldner@usask.ca

John Campbell (University of Saskatchewan, Western College of Veterinary Medicine), Sheryl Gow (Public Health Agency of Canada, Western College of Veterinary Medicine)

Status Project Code
In progress. Results expected in April, 2023 SURV.03.20


Earlier research conducted by this team through the Western Canadian Cow-Calf Surveillance Network found that respiratory disease was a leading cause for antibiotic use in calves before (and after) weaning. Subsequently, the BCRC supported a follow-up project to look at antibiotic use and resistance based on fecal samples collected from cows and calves in Western Canadian herds participating in the Canadian Cow Calf Surveillance Network. This project will add a component to that project, looking at respiratory disease bacteria.


  •  describe antibiotic resistance in respiratory pathogens in cow-calf herds using traditional culture techniques,
  • assess the potential association between antibiotic use in cow-calf herds and antibiotic resistance in BRD pathogens in calves before entering the feedlot,
  • evaluate emerging metagenomics tools to identify opportunities for more cost effective surveillance, and
  • assess the potential association between key management variables in cow-calf herds and BRD pathogens and AMR in BRD pathogens for calves entering the feedlot.

What they will do

This team will collect samples of respiratory pathogens (Mannheimia, Histophilus and Pasteurella) and test them for antibiotic resistance using the same protocols that CIPARS is uses in its feedlot surveillance initiative. 26 calves will be sampled in each of 32 herds. Antibiotic resistance in the respiratory pathogens will be compared to antibiotic resistance in the fecal bacteria. They will also examine whether pooled sampling can provide a less costly but equally accurate estimate of antibiotic resistance as testing individual samples. They’ll also assess whether genomic-based testing can provide faster and less costly antibiotic susceptibility results than culture-based techniques. They will look at relationships between antibiotic use and resistance, as well as with vaccination and weaning practices.


Effective antibiotics are important tools to treat BRD in calves both pre- and post-weaning. The results of this trial will inform messaging to producers and veterinarians regarding antimicrobial stewardship in cow-calf herds.