Location: Meat Safety and QualityTitle: Effects of in-feed Chlortetracycline Prophylaxis of beef cattle on animal health and antimicrobial-resistant Escherichia coli
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/17/2017
Publication Date: 2/28/2017
Citation: Agga, G.E., Schmidt, J.W., Arthur, T.M. 2017. Effects of in-feed Chlortetracycline Prophylaxis of beef cattle on animal health and antimicrobial-resistant Escherichia coli. Meeting Abstract. [Abstract]. Beef Industry Safety Summit, February 28-March 2, 2017, Houston, Texas, Available:http://bifsco.org/search.aspx?qal=2017 abstracts.
Technical Abstract: Objective: The objective of this study was to evaluate the effect of a one-time, five-day in-feed CTC prophylaxis on animal health (morbidity and body weight gain), occurrence of TETr E. coli, and occurrence of 3GCr E. coli over a four-month follow-up period. Experimental Design & Analysis: 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; 30 hd/pen x 5 pens) received no CTC, while a "CTC group" (n = 150) received in-feed CTC (10 mg/lb of body weight/day) from the 5th to the 9th day after feedlot arrival. Key Results: Over 25% (38/150) of the animals in the control group developed illnesses requiring therapeutic treatment with antimicrobials critically important to human medicine. Only two animals (1.3%) in the CTC group required such treatments. Fecal swab and pen surface occurrences of generic E. coli, 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 (P < 0.01). 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 for fecal or pen surface samples on any sample occasion. 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. How can this information be applied in the industry? Direct evidence relating the use of antimicrobials in livestock production to diminished human health outcomes due to antimicrobial resistance is lacking, hence the U.S. Food and Drug Administration has taken an approach to maximize therapeutic efficacy and minimize selection of resistant microorganisms through judicious use of antimicrobials. This study demonstrated that prophylactic in-feed treatment of chlortetracycline administered for five days to calves entering feedlots is judicious as this therapy reduced animal morbidity, reduced the use of antimicrobials more critical to human health, and had no long-term impact on the occurrence of antimicrobial-resistant E. coli.