Antimicrobial resistance in bovine respiratory disease

Antimicrobials are important tools in modern beef production. Antimicrobial drugs are often used for metaphylaxis to prevent and treat early cases of bovine respiratory disease complex (BRD) as well as for therapeutic purposes in feedlot cattle. Antimicrobial resistance of bovine respiratory pathogens can result in treatment failures and losses associated with increased treatment costs and mortalities. Mixing of cattle from multiple sources within auction markets has always been a significant risk factor for BRD. The stress of establishing a social dominance hierarchy along with the mixing of pathogens from a variety of farm sources can increase the risk of BRD in weaned calves. One method feedlots have used to mitigate this risk is to reduce mixing stress by purchasing calves directly from the ranch rather than through the auction market. The objective of this study was to describe the prevalence and antimicrobial sensitivity of 3 major bovine respiratory disease (BRD) bacterial pathogens at arrival and again later in the feeding period in feedlot calves derived from the auction market and from a single ranch source.