The Effect of Metaphylactic Antimicrobial Use on the Development of Antimicrobial Resistance in Fecal E. coli Isolates of Feedlot Cattle

Abstract

Much of the long-term economic and environmental stability of beef production seems to be driven by marketplace issues such as food safety and quality assurance that would include the potential presence of antimicrobial resistant bacteria. Long-acting injectable antimicrobials are widely used for metaphylaxis in calves on arrival at the feedlot. Previous feedlot trials by other researchers have associated metaphylaxis with lowered rates of morbidity and mortality from respiratory disease. Average daily gain, feed efficiency, case fatality rates, treatment rates, and relapse rates for bovine respiratory disease have also improved in animals where metaphylaxis is used. Metaphylaxis, therefore, has great industry significance from both an economic and animal welfare perspective. The objectives of this study were: 1) to determine the prevalence of fecal E. coli resistant to antimicrobials in auction-mart derived weaned calves, 2) to determine the effect of metaphylactic antimicrobial usage on the development of fecal E. coli resistant to various antimicrobials, and 3) to determine the persistence of antimicrobial resistant fecal E. coli and to evaluate the potential risk of their presence preslaughter.