Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2009
Publication Date: 9/1/2009
Citation: Brown Brandl, T.M., Berry, E.D., Wells, J., Arthur, T.M., Nienaber, J.A. 2009. Impacts of Individual Animal Response to Heat and Handling Stresses on Escherichia coli and E. coli O157:H7 Fecal Shedding by Feedlot Cattle. Foodborne Pathogens and Disease. 6(7):855-864. Interpretive Summary: Cattle are an important source of E. coli O157:H7, a pathogen that can cause human foodborne illness. Reducing this pathogen in cattle will require understanding the factors that affect the infection and shedding of E. coli O157:H7 by cattle. Cattle stress is one factor that could potentially affect pathogens in livestock. The objectives of this study were to investigate the effects of heat and handling stress levels on the presence and the amount of E. coli O157:H7 in the feces of feedlot cattle. Cattle were evaluated during the summer in each of two years. There was no evidence of a relationship between cattle stress levels and E. coli O157:H7 in feces, indicating that neither heat nor handling stress contributes to the food safety risk associated with cattle that carry E. coli O157:H7.
Technical Abstract: The reduction of foodborne pathogens in cattle destined for human consumption will require knowledge of the factors that impact the carriage and shedding of these organisms. The effects of heat and handling stress levels on the fecal shedding of Escherichia coli O157:H7 and generic E. coli by feedlot cattle were investigated. In year one, 128 feedlot heifers were evaluated for heat tolerance five times per week during the 84-day finishing period from May through August. Heat stress measurements included respiration rate, panting score, and visual assessments. In year two, panting scores were taken for a group of 256 finishing feedlot heifers on days in July and August for which the temperature humidity index (THI) was predicted to be in the “emergency” category (THI was greater than or equal to 84). For both years, animals were weighed and temperament scored on a 28-day schedule. At the same time, rectal feces samples were collected from each animal individually. The presence and levels of E. coli O157:H7 and levels of generic E. coli in feces were determined. There were no clear trends between the heat stress or handling stress levels and fecal generic E. coli concentrations or E. coli O157:H7 concentration or prevalence in feces, indicating that neither heat nor handling stress impact the food safety risk associated with E. coli O157:H7-positive cattle.