Tulathromycin metaphylaxis increases prevalence of multidrug resistant Mannheimia haemolytica while improving health in stocker calves

Abstract

Bovine respiratory disease (BRD) is commonly controlled by metaphylaxis, but increasing prevalence of antimicrobial re­sistant (AMR) Mannheimia haemolytica (MH) may decrease ef­ficacy. The objective of this study was to determine the effect of macrolide metaphylaxis on 1) morbidity and mortality in stocker cattle over a 21-day period and 2) isolation rate and anti­microbial susceptibility of MH at arrival (d0) and d21.