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P3-230 E. coli O157:H7 Fecal Shedding in Backgrounder Steers Fed with Different Dietary Crude Protein Levels

Tuesday, July 28, 2015
Hall B (Oregon Convention Center)
Xuan Zhang , University of Manitoba, Food Science Faculty , Winnipeg , Canada
Kristine Blair , University of Manitoba , Winnipeg , Canada
Kim Ominski , University of Manitoba, Animal Science Department , Winnipeg , Canada
Argenis Rodas-Gonzalez , University of Manitoba , Winnipeg , Canada
Mueen Aslam , Agriculture & Agri-Food Canada , Lacombe , Canada
Karin Wittenberg , University of Manitoba , Winnipeg , Canada
Claudia Narvaez-Bravo , University of Manitoba, Food Science Department , Winnipeg , Canada
Introduction: Shiga Toxin-producing Escherichia coli comprise a diverse group of bacteria capable of causing severe gastrointestinal disease in humans. Prior research has suggested that E. coli O157:H7 prevalence varies according to the type of diet (fiber vs. starch) fed to cattle. In addition, the protein content in forage diets may also play an important role in O157:H7 fecal shedding.

Purpose: Evaluate the effect of different dietary crude protein concentrations on E. coli O157:H7 fecal shedding in beef cattle.

Methods:  A total of 192 fecal samples were collected from beef steers fed with forage diets, plus the addition of barley straw, canola meal, and corn silage, to adjust dietary crude protein (CP) levels (CP; T1 = 6.9%, T2 = 10.3%, T3 = 12.1%, and T4 = 13.6%). Similar energy and fiber contents were maintained among the treatments (NDF: T1 = 56, T2 = 54.7%, T3 = 56.9 and T4 = 57.3). E. coli O157:H7 detection and confirmation was carried out using conventional microbiology techniques, immunomagnetic separation, latex agglutination and multiplex PCR (rfbE, flicH7, stx1 and stx2 genes).

Results: Overall 21.9% (42/191) of the animals tested positive for E. coli O157. A total of 42 strains were positive for O157 latex agglutination and were further confirmed with PCR (rfbE positives). All isolates were positive for sorbitol and β-glucuronidase, and therefore considered atypical. Results indicated that 15 of these strains were O157:H12 and negative for stx1-2 genes. Chi-square analysis indicated that the distribution differed among dietary CP levels (P < 0.05); where T2 showed the highest percentage of E. coli O157, 36.2% (17/47), followed by T1: 22.9 (11/48), T3: 22.9 % (11/48) and T4 with the lowest prevalence 6.3% (3/48).

Significance: Results suggest that protein content in the diet may influence E. coli O157 fecal shedding in cattle as cattle fed a diet containing 13.6% CP had lower prevalence than cattle fed diets containing 6.9, 10.3 and 12.1% CP.

Back to: Poster Session 3 – Laboratory and Detection Methods, Sanitation; Antimicrobials; Produce; Epidemiology
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