title: Influence of beta-agonists (ractopamine HCl and zilpaterol HCl) on fecal shedding of Escherichia coli O157:H7 in feedlot cattle.
abstract: Ractopamine HCl and zilpaterol HCl, beta-agonists recently approved for use in feedlot cattle to improve performance traits and carcass leanness, were examined for their effects on fecal shedding of Escherichia coli O157:H7 in feedlot cattle. Fecal samples (n = 2,454) were obtained from four experiments (one ractopamine HCl, three zilpaterol HCl) over the course of a 3-year period, either by rectal palpation (ractopamine HCl experiment) or from pen-floor fecal pats. Samples were cultured quantitatively and qualitatively for E. coli O157:H7. No significant treatment differences were detected for fecal prevalence of E. coli O157:H7 in the ractopamine HCl experiment. Zilpaterol HCl feeding had no effect (P > 0.20) on fecal shedding in the first or second experiments, with overall E. coli O157:H7 prevalence relatively low (<7%). In the third zilpaterol HCl experiment, the percentage of fecal samples that were E. coli O157:H7 positive following qualitative culture was higher (P < 0.05) in the zilpaterol HCl treatment (10.3%) than for the control (6.1%). The current research showed minimal effects of beta-agonists on fecal shedding of E. coli O157:H7 and indicated that these compounds (fed immediately prior to slaughter) are not a cause for concern from a food safety standpoint.
authors.affiliation: Food and Feed Safety Research Unit, Agricultural Research Service, U.S. Department of Agriculture, College Station, Texas 77845, USA. edrington@ffsru.tamu.edu
authors.forename: Tom S
authors.initials: TS
authors.lastname: Edrington
authors.forename: Russell L
authors.initials: RL
authors.lastname: Farrow
authors.forename: Guy H
authors.initials: GH
authors.lastname: Loneragan
authors.forename: Sam E
authors.initials: SE
authors.lastname: Ives
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Engler
authors.forename: John J
authors.initials: JJ
authors.lastname: Wagner
authors.forename: Marilyn J
authors.initials: MJ
authors.lastname: Corbin
authors.forename: William J
authors.initials: WJ
authors.lastname: Platter
authors.forename: David
authors.initials: D
authors.lastname: Yates
authors.forename: John P
authors.initials: JP
authors.lastname: Hutcheson
authors.forename: Richard A
authors.initials: RA
authors.lastname: Zinn
authors.forename: Todd R
authors.initials: TR
authors.lastname: Callaway
authors.forename: Robin C
authors.initials: RC
authors.lastname: Anderson
authors.forename: David J
authors.initials: DJ
authors.lastname: Nisbet
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology*; D019453:Escherichia coli O157; D005243:Feces / Q000382:microbiology*; D010627:Phenethylamines / Q000494:pharmacology*; D014297:Trimethylsilyl Compounds / Q000494:pharmacology*
chemical_list: D000318:Adrenergic beta-Agonists; D010627:Phenethylamines; D014297:Trimethylsilyl Compounds; C475840:Zilpaterol; C060897:ractopamine