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


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
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
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.

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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

<P> For complete projects details, view the <a href="…; target="_blank">Project Summary. </a>

Miller, Rhonda; Anderson, Robin
Texas A&M University
USDA - Agricultural Research Service
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