Efficacy of a vaccine and a direct-fed microbial against fecal shedding of Escherichia coli O157:H7 in a randomized pen-level field trial of commercial feedlot cattle.
Our primary objective was to determine the efficacy of a siderophore receptor and porin proteins-based vaccine (VAC) and a Lactobacillus acidophilus-based direct-fed microbial (DFM) against fecal shedding of Escherichia coli O157:H7 in commercial feedlot cattle fed a corn grain-based diet with 25% distiller's grains. Cattle projected to be on a finishing diet during the summer were randomly allocated into 40 study pens within ten blocks based on allocation dates. Blocks were complete; each of the four pens within a block was randomly assigned one treatment: control, VAC, DFM, or VAC+DFM. The DFM was fed (10⁶CFU/animal/day of Lactobacillus) throughout the study periods (84-88 days) and cattle were vaccinated at enrollment and again three weeks later. Fresh fecal samples (30/pen) from pen floors were collected weekly for four consecutive weeks (study days 52-77). Two concurrent culture procedures were used to enable estimates of E. coli O157:H7 shedding prevalence and prevalence of high shedders. From 4800 total samples, 1522 (31.7%) were positive for E. coli O157:H7 and 169 (3.5%) were considered high shedders. Pen-level linear mixed models were used for data analyses. There were no significant interactions among treatments and time of sampling. However, vaccinated pens had lower (P<0.01) overall prevalence of E. coli O157:H7 (model-adjusted mean ± SEM=17.4 ± 3.95%) and lower (P<0.01) prevalence of high shedders (0.95 ± 0.26%) than unvaccinated pens (37.0 ± 6.32% and 4.19 ± 0.81%, respectively). There was no evidence of a DFM effect on either measure of E. coli O157:H7 shedding. Results indicate that a two-dose regimen of the vaccine significantly reduces fecal prevalence of E. coli O157:H7 (vaccine efficacy of 53.0%) and prevalence of E. coli O157:H7 high shedders (vaccine efficacy of 77.3%) in commercial feedlot cattle reared in the summer on a finishing diet with 25% distiller's grains.
Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA.
Charley A
CA
Cull
Zachary D
ZD
Paddock
T G
TG
Nagaraja
Nora M
NM
Bello
Abram H
AH
Babcock
David G
DG
Renter
D000821:Animal Feed / Q000382:microbiology*; D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000276:immunology; D057138:Bacterial Shedding; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology / Q000517:prevention & control*; D004927:Escherichia coli Infections / Q000517:prevention & control / Q000662:veterinary*; D019453:Escherichia coli O157 / Q000302:isolation & purification* / Q000472:pathogenicity; D022361:Escherichia coli Vaccines / Q000627:therapeutic use*; D005243:Feces / Q000382:microbiology*; D008297:Male; D018272:Porins / Q000276:immunology; D011956:Receptors, Cell Surface / Q000276:immunology
D001425:Bacterial Outer Membrane Proteins; D022361:Escherichia coli Vaccines; D018272:Porins; D011956:Receptors, Cell Surface; C035902:siderophore receptors