Antimicrobial resistance in bovine respiratory disease: Auction market- and ranch-raised calves.

Abstract

This study compared changes in prevalence and antimicrobial susceptibility of, andin feedlot calves derived from the auction market (AUCT;= 299) and from a single-ranch source (RANCH;= 300). In the AUCT calves, the prevalence ofdecreased, whereasincreased over the feeding period. The AUCT calves showed an increase in isolates not susceptible to tulathromycin for all bovine respiratory disease (BRD) pathogens, an increase inandisolates not susceptible to oxytetracycline, and an increase inisolates not susceptible to florfenicol. In the RANCH calves, the prevalence of all 3 BRD pathogens was high at feedlot entry and decreased significantly during the study period. In RANCH calves, there was a significant increase inisolates not susceptible to oxytetracycline, tulathromycin, and florfenicol. Surprisingly, there was a significant decrease inisolates that were not susceptible to oxytetracycline, tilmicosin, and tulathromycin.