Influence of beta-agonists (ractopamine HCl and zilpaterol HCl) on fecal shedding of Escherichia coli O157:H7 in feedlot cattle.
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.
Edrington
Tom S
TS
Food and Feed Safety Research Unit, Agricultural Research Service, U.S. Department of Agriculture, College Station, Texas 77845, USA. edrington@ffsru.tamu.edu
Farrow
Russell L
RL
Loneragan
Guy H
GH
Ives
Sam E
SE
Engler
Michael J
MJ
Wagner
John J
JJ
Corbin
Marilyn J
MJ
Platter
William J
WJ
Yates
David
D
Hutcheson
John P
JP
Zinn
Richard A
RA
Callaway
Todd R
TR
Anderson
Robin C
RC
Nisbet
David J
DJ
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*
D000318:Adrenergic beta-Agonists; D010627:Phenethylamines; D014297:Trimethylsilyl Compounds; C475840:Zilpaterol; C060897:ractopamine