Challenges of Pathogen Control in Beef Cattle Production and Processing in South Texas



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This multi-phase project was designed (1) to evaluate existing post-harvest process controls and intervention strategies used to reduce Escherichia coli O157:H7, (2) to evaluate the impacts of cattle source and environmental factors on Salmonella prevalence in bovine lymph nodes, and (3) to evaluate sanitary conditions of feedyards in South Texas. The ultimate goal of this project was to identify and implement measures that reduce E. coli O157:H7 in beef harvest facilities, and Salmonella prevalence in feedyards. To evaluate process control of E. coli O157:H7 throughout the beef harvest process, samples were collected from harvest floor processing areas at two commercial beef slaughter establishments, and enumerated for aerobic plate counts, E. coli/coliform, and Enterobacteriaceae. To survey existing Salmonella prevalence, bovine lymph nodes (n = 307) were collected from beef carcasses at a commercial beef processing plant. Lymph nodes were extracted from cattle sourced from seven feedyards. Salmonella prevalence in lymph nodes was found to be 0% in cattle sourced from only one of the seven yards. Lymph nodes from cattle sourced from the other feedyards yielded positive samples, with varying prevalence. Of the remaining six feedyards, one feedyard yielded 88.2% prevalence of Salmonella in bovine lymph nodes, which was significantly higher than all other feedyards (42.9, 40.0, 40.0, 24.0, and 4.0%). The prevalence of Salmonella in the feedlot environment was compared among three feedyards; one yard had 65.0% environmental prevalence of Salmonella, which was statistically higher than the other feedyards surveyed. Of the two remaining yards, one had 0% prevalence of Salmonella in fecal and soil samples, which was also the feedyard with 0% prevalence of Salmonella in lymph nodes. Findings include (1) the significance of effective sanitary dressing procedures and intervention strategies in a beef harvest environment, (2) that there is clear feedyard-to-feedyard variation with relation to Salmonella prevalence in bovine lymph nodes, and (3) that differences in environmental factors existed among feedyards although the reasons remain unclear.