Evaluation of Commercial β-Agonists, Dietary Protein, and Shade on Fecal Shedding of Escherichia coli O157:H7 from Feedlot Cattle

Abstract Escherichia coli O157:H7 is a foodborne pathogen commonly associated with cattle feces. Diet, including dietary supplements such as β-agonists, may impact fecal shedding of this pathogen. A series of three experiments were conducted to determine if the β-agonists ractopamine hydrochloride (RAC) or zilpaterol hydrochloride (ZH) would impact the level or prevalence of fecal E. coli O157:H7 shedding. In Experiment 1, dietary RAC did not impact fecal shedding of E. coli O157:H7 based on the level or prevalence, but the addition of dietary soybean meal (SBM) in the study did reduce E. coli O157:H7 shedding. In Experiments 2 and 3, dietary ZH did not affect fecal E. coli O157:H7 shedding as determined by enumeration or prevalence, but in Experiment 2 the addition of 30% (dry matter basis) wet distillers grains with solubles (WDGS) in the diet tended to increase E. coli O157:H7 shedding. Shade is a potential management tool to reduce heat stress in cattle, and in Experiment 3 the presence of shade over ...