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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Environmental Microbial & Food Safety Laboratory » Research » Research Project #436659

Research Project: Antimicrobial Resistance in the Gut Microflora of Young Calves

Location: Environmental Microbial & Food Safety Laboratory

Project Number: 8042-32420-008-002-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Aug 1, 2019
End Date: Jul 31, 2024

The long-term goal is to develop mitigation strategies for reducing the prevalence of antimicrobial-resistant bacteria in dairy animals and their environments. Previous research identified young calves as the primary source of resistant bacteria in dairy herds. The specific objective of this project is to characterize the antimicrobial resistance of fecal bacteria in calves from birth through the post-weaning growth phase.

An experiment will be conducted to characterize antimicrobial resistant bacteria in the gut of dairy calves from birth through weaning. To characterize the impact of weaning age, calves will be weaned at two different time points (7 weeks vs. 10 weeks) and will be reared with milk replacer or milk replacer that is artificially supplemented with antibiotics to mimic the potential for feeding waste milk to impact resistance in gut bacteria. Calves (50 in total) will be sourced from one or more commercial dairy herds and housed in individual pens for the duration of the study. Fecal samples will be collected from each animal during the study and cultured for E. coli and Salmonella. Bacterial isolates will be characterized (phenotypically and genotypically) for resistance to the NARMS panel of antibiotics. The microbiome and resistome of a select set of fecal samples will be will also be characterized. Based on the results of the first experiment, sampling will be conducted on additional commercial dairy herds to further define management practices that impact colonization of the calves and older animals with antimicrobial-resistant bacteria.