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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Meat Safety & Quality Research » Research » Publications at this Location » Publication #329906

Research Project: Mitigation Approaches for Foodborne Pathogens in Cattle and Swine for Use During Production and Processing

Location: Meat Safety & Quality Research

Title: Effects of in-feed chlortetracycline prophylaxis of beef cattle on animal health and antimicrobial-resistant Escherichia coli

Author
item Agga, Getahun
item Schmidt, John
item Arthur, Terrance

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/3/2016
Publication Date: 11/28/2016
Publication URL: http://handle.nal.usda.gov/10113/63314
Citation: Agga, G.E., Schmidt, J.W., Arthur, T.M. 2016. Effects of in-feed chlortetracycline prophylaxis of beef cattle on animal health and antimicrobial-resistant Escherichia coli. Applied and Environmental Microbiology. 82(24):7197-7204. doi:10.1128/AEM.01928-16.

Interpretive Summary: Concerns have been raised that in-feed use of antimicrobials in livestock feed may increase antimicrobial resistance (AMR) in bacteria associated with livestock and livestock environments. Chlortetracycline (CTC) is an antimicrobial commonly fed to calves shortly after entry into feedlots. This treatment is given for prevention of bovine respiratory disease. We evaluated the impact of a 5-day in-feed CTC regimen on animal health and antimicrobial resistance in bacteria. A control group of cattle (n = 150) did not receive CTC, while a treated group (n = 150) received in-feed CTC from the 5th to the 9th day after feedlot arrival. Fecal swab and pen surface occurrences of AMR E. coli were determined on five sample occasions: arrival at the feedlot, 5 days post treatment completion (5 dpt), 27 dpt, 75 dpt, and 117 dpt. On 5 dpt, there was an increase in AMR E. coli for the treated group vs. the control group. For all other sample dates there was no difference between the two groups. In addition, there was significantly higher number of illnesses in the cattle that were not treated with CTC when compared to those animals that received CTC. In conclusion in-feed CTC treatment reduces the number of illnesses in calves entering feedlot facilities with no long-term impact on the occurrence of AMR E. coli.

Technical Abstract: Concerns have been raised that in-feed chlortetracycline (CTC) may increase antimicrobial resistance (AMR), specifically tetracycline-resistant (TETr) Escherichia coli, and third-generation cephalosporin-resistant (3GCr) E. coli. We evaluated the impact of a 5-day in-feed CTC prophylaxis on animal health, TETr E. coli, and 3GCr E. coli. A "control group" of cattle (n = 150) that received no CTC, while a "CTC group" (n = 150) received in-feed CTC from the 5th to the 9th day after feedlot arrival. Fecal swab and pen surface occurrences of generic E. coli (E. coli regardless of AMR status), TETr E. coli, and 3GCr E. coli were determined on five sample occasions: arrival at the feedlot, 5 days post treatment completion (5 dpt), 27 dpt, 75 dpt, and 117 dpt. On 5 dpt, TETr E. coli concentrations were higher for the CTC group than control group. On 27 dpt, 75 dpt, and 117 dpt TETr E. coli concentrations did not differ between groups. 3GCr E. coli occurrences did not differ between control and CTC groups on any sample occasion. Cattle morbidity and therapeutic use of antimicrobials critically important to human medicine were lower for the CTC-treated group. For both groups generic, TETr, and 3GCr E. coli occurrences were highest on 75 dpt and 117 dpt, suggesting that factors other than in-feed CTC contributed more significantly to antimicrobial-resistant E. coli occurrence. In conclusion, a 5-day in-feed CTC treatment reduces morbidity and therapeutic antimicrobial use in feedlot cattle with no long-term impact on the occurrence of antimicrobial-resistant E. coli.