Long-term effects of systemic ceftiofur and ampicillin on the abundance and duration of shedding resistant Gram-negative bacteria in the feces of healthy dairy cows: A randomized clinical trial

The objective was to determine if systemic ceftiofur and ampicillin administration affect abundance and duration of resistant Gram-negative bacteria found in the feces of healthy dairy cows. As an additional objective, we compared the abundance of Gram-negative-resistant bacteria and antimicrobial resistance genes in cows that received treatment with ampicillin or ceftiofur or remained untreated.