|Schroeder, S - TX A&M UNIVERSITY|
|Rosenkrans, JR., C - UNIVERSITY OF AR|
|Flores, R - UNIVERSITY OF AR|
Submitted to: American Society of Animal Science Proceedings
Publication Type: Proceedings
Publication Acceptance Date: May 6, 2004
Publication Date: June 17, 2004
Citation: Schroeder, S.B., Edrington, T.S., Looper, M.L., Schultz, C.L., Rosenkrans, Jr., C.F., Flores, R., Callaway, T.R., Anderson, R.C., Nisbet, D.J. 2004. Incidence of foodborne pathogens and antimicrobial susceptibility of fecal coliforms in stocker calves fed ionophore. Proceedings of Western Section of American Society of Animal Science. 55:353-356. Interpretive Summary: Ionophores are antibiotics that improve the growth and performance of young cattle. The use of ionophores in cattle production is very common. The emergence of food sickness cause by E. coli O157:H7 began at about the same time that ionophores started to be fed and this has raised concerns. The purpose of the present study was to determine if feeding an ionophore to grazing cattle for 60 days had any effect on Salmonella or E. coli O157:H7. We also examined the ability of antibiotics to kill fecal coliforms isolated from these animals fed ionophore. Results showed no effect of ionophore feeding on fecal shedding of E. coli O157:H7 or Salmonella when fed for 60 days. Furthermore, feeding ionophores had no affect on the ability of antibiotics to kill fecal coliforms.
Technical Abstract: Fifty-three crossbred calves (232 ± 3 kg) were purchased from auction barns to determine: 1) incidence of fecal shedding of E. coli O157:H7 and Salmonella, 2) influence of feeding an ionophore on shedding of E. coli O157:H7 and Salmonella, and 3) antimicrobial resistance of putative fecal coliforms isolated from calves receiving ionophore. Calves were blocked by BW and sex, and assigned in replicate, to receive mineral with ionophore (IONOPH; Lasalocid; 1.76 g/kg mineral) or without ionophore (CONTROL) for 60 d. Calves were fed a corn:wheat midds:soybean meal supplement at 1.5% BW/d. Fecal samples were collected and BW recorded on d 0, 33 and 60. Antimicrobial susceptibility of fecal coliforms (n = 11 or 12/treatment) to 14 antibiotics was determined on each collection date. Average daily gain (ADG) was not different (P > 0.10) between treatments and averaged 0.92 ± 0.07 kg/d for IONOPH calves and 0.87 ± 0.07 kg/d for CONTROL calves. Sick calves had decreased (P < 0.05) ADG compared with healthy calves (0.78 ± 0.10 vs 1.01 ± 0.06 kg/d). Incidence of E. coli O157:H7 was 1.9% and was not different among treatments (P > 0.10). No Salmonella was isolated from any calf during the experimental period. Patterns of antimicrobial resistance were similar (P = 0.14) between IONOPH and CONTROL calves. Isolates demonstrated the most resistance to oxytetracycline, chlorotetracycline, ampicillin and florfenicol (33, 29, 28 and 26% of isolates resistant, respectively). All calves were fed chlorotetracyline in the receiving ration for 10 d and a number of calves in both treatments were administered florfenicol for respiratory illness during the experiment. Feeding ionophore to stocker calves had no affect of fecal shedding of foodborne pathogens or on antimicrobial resistance in fecal coliforms.