Efficacy of a vaccine and a direct-fed microbial against fecal shedding of Escherichia coli O157:H7 in a randomized pen-level field trial of commercial feedlot cattle

► We evaluated efficacy of interventions against E. coli O157 fecal shedding in cattle. ► A siderophore receptor and porin protein vaccine reduced shedding by >50%. ► The vaccine also reduced the prevalence of high shedders by >75%. ► A direct-fed microbial had no significant effect on fecal shedding.