Effect of finishing diets on Escherichia coli populations and prevalence of enterohaemorrhagic E. coli virulence genes in cattle faeces.
OBJECTIVE
To determine the effect of different carbohydrate-based finishing diets on fermentation characteristics and the shedding of Escherichia coli and enterohaemorrhagic E. coli (EHEC) virulence genes in cattle faeces.


RESULTS
The size of faecal E. coli populations and fermentation characteristics were ascertained in three experiments where cattle were maintained on a range of finishing diets including high grain, roughage, and roughage + molasses (50%) diets. Increased E. coli numbers, decreased pH and enhanced butyrate and lactate fermentation pathways were associated with grain diets, whereas roughage and roughage + molasses diets resulted in decreased concentrations of ehxA, eaeA and stx(1) genes, this trend remaining at lairage. In one experiment, faecal E. coli numbers were significantly lower in animals fed roughage and roughage + molasses, than animals fed grain (4.5, 5.2 and 6.3 mean log10 g(-1) digesta respectively). In a second experiment, faecal E. coli numbers were 2 log lower in the roughage and roughage + molasses diets compared with grain-fed animals prior to lairage (5.6, 5.5 and 7.9 mean log10 g(-1) digesta respectively) this difference increasing to 2.5 log at lairage.


CONCLUSIONS
The type of dietary carbohydrate has a significant effect on E. coli numbers and concentration of EHEC virulence genes in faeces of cattle.


CONCLUSIONS
The study provides a better understanding of the impact finishing diet and commercial lairage management practices may have on the shedding of E. coli and EHEC virulence factors, thus reducing the risk of carcass contamination by EHEC.
Gilbert
R A
RA
CSIRO Livestock Industries, Queensland Bioscience Precinct, Brisbane, Qld, Australia. ros.gilbert@csiro.au
Tomkins
N
N
Padmanabha
J
J
Gough
J M
JM
Krause
D O
DO
McSweeney
C S
CS
D000821:Animal Feed / Q000382:microbiology*; D000818:Animals; D002087:Butyrates / Q000378:metabolism; D002417:Cattle; D015169:Colony Count, Microbial / Q000379:methods; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004043:Dietary Fiber; D002523:Edible Grain; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development* / Q000472:pathogenicity; D005243:Feces / Q000382:microbiology*; D005285:Fermentation; D005798:Genes, Bacterial / Q000235:genetics*; D006863:Hydrogen-Ion Concentration; D007773:Lactates / Q000378:metabolism; D008965:Molasses; D014774:Virulence / Q000235:genetics
D002087:Butyrates; D004040:Dietary Carbohydrates; D004043:Dietary Fiber; D007773:Lactates