Effect of subtherapeutic administration of antibiotics on the prevalence of antibiotic-resistance Escherichia coli bacteria in Feedlot cattle

The collection of 3,300 fecal samples over a 314-day period was utilized to study the antibiotic-resistant Escherichia coli in 300 feedlot steers which received subtherapeutic levels of antibiotics. The results showed that the subtherapeutic administration of tetracycline in combination with sulfamethazine increased the prevalence of tetracycline- and ampicillin-resistant E. coli in cattle.