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Assessment of Nitroethane to Reduce E. coli O157:H7,
Salmonella and Campylobacter in Fed Cattle

Investigators
Miller, Rhonda; Anderson, Robin
Institutions
Texas A&M University
USDA - Agricultural Research Service
Start date
2005
End date
2006
Objective
The bovine gastrointestinal tract is a reservoir for E. coli O157:H7, Salmonella, and to a lesser extent, Campylobacter. Cross-contamination from the intestinal track to the carcass can occur during harvesting and fabrication. Postharvest interventions developed to kill pathogens on the carcass have been very effective, but can be overwhelmed if cattle entering the slaughter facility have too much existing contamination. Practical preharvest interventions are needed to compliment the industry’s multi-hurdle approach to pathogen reduction and elimination. Quantitative risk assessments indicate such interventions would reduce human exposure to pathogens. U.S. Department of Agriculture (USDA) researchers have developed a chlorate product that exploits the ability of E. coli and Salmonella to utilize nitrate. This strategy selectively targets bacteria possessing the enzyme nitrate reductase so that these pathogens are killed but beneficial anaerobes lacking the enzyme are unharmed. The selective bactericidal activity has been demonstrated both in vitro and in vivo. A nitrate preconditioning period has been shown to enhance the bactericidal effect of chlorate in broilers and pigs; however because of the rapid reduction of nitrate in the rumen, this strategy is not practical in cattle. The researchers proposed that using nitrocompounds, rather than nitrate, might still be effective in enhancing the bactericidal effect of chlorate. Nitroethane is a relatively innocuous compound that can also improve gross energy utilization, thus giving producers a cost-effective preharvest intervention. The objectives of this project were to obtain fundamental information on the absorption, passage and ruminal and gastrointestinal metabolism of nitroethane. This information will help determine if this can be developed into a practical and cost-effective preharvest intervention technology.
More information
Contrary to findings from numerous laboratory studies, results of this study did not support the hypothesis that nitroethane combined with chlorate would reduce Campylobacter and Salmonella in feedlot cattle. The researchers indicated this could be due to a rapid absorption and rumen degradation that prevented the accumulation of nitroethane to levels needed to be effective against enteropathogens. Feeding chlorate in the last day’s ration reduced fecal E. coli concentrations by more than 1,000-fold, but this was not enhanced by prior nitroethane treatment. The nitroethane treatments did reduce methane-producing activity (an indirect measure of numbers of methane-producing bacteria) in the rumen contents of range and feedlot cattle.

For complete projects details, view the Project Summary.

Funding Source
Nat'l. Cattlemen's Beef Assoc.
Project number
BC-2005-1
Categories
Escherichia coli
Bacterial Pathogens