Location: Meat Safety and Quality
2023 Annual Report
Accomplishments
1. Antimicrobial resistance in metaphylactic antimicrobial treated cattle. Feedlot cattle at high risk to develop bovine respiratory disease are commonly treated with antimicrobials at arrival to reduce respiratory illnesses. Little is known about the impact of antimicrobial use on feedlot cattle at arrival on the development and persistence of antimicrobial resistance in treated cattle. In collaboration with scientists at Texas Tech University and ARS scientists in Lubbock, Texas, ARS scientists in Clay Center, Nebraska, treated high risk cattle at arrival with saline or one of three antimicrobials. Type of antimicrobial impacted the initial resistant E. coli populations over the course of the study. However, by the end of the study, antimicrobial resistant E. coli populations were similar across all treatments. The use of antimicrobials at arrival also had no impact on the development or persistence of resistant Salmonella. Antimicrobial resistance in this study was not associated with use of a metaphylactic antimicrobial in cattle on arrival at the feedlot.
2. Impact of antimicrobial use on Salmonella in feedlot cattle. Feedlot cattle can be a significant source of Salmonella in the food chain. In collaboration with scientists at Texas Tech University and ARS scientists in Lubbock, Texas, ARS scientists in Clay Center, Nebraska, monitored Salmonella in feces from arrival to harvest of cattle treated at arrival with saline or one of three antimicrobials (tulathromycin, ceftiofur or florfenicol). Cattle treated with tulathromycin had significantly higher fecal and hide prevalence of Salmonella throughout the 8-month study compared to cattle treated with ceftiofur or florfenicol. However, Salmonella presence in the lymph nodes was not affected by antimicrobial treatment. The use of tulathromycin as a treatment for cattle at arrival to the feedlot may increase the amount of Salmonella detected in the feces and pen environments, thus feedlot cattle producers, beef processors, and consumers would benefit from using alternative antimicrobials when possible.
