Corn-stuff may increase E. coli O157 in cattle

Inclusion of distillers’ grains (DGs) has been associated with
increased prevalence of Escherichia coli O157:H7 in cattle housed in
research settings. Our objective was to quantify the relationship
between inclusion of DGs in commercial feedlot rations and the burden
of E. coli O157.

A convenience sample of 10 feedlots was enrolled based on DG use in finishing diets; 1 cohort included 5 feedlots in which DGs were greater than 15% of the dietary dry matter and the other cohort consisted of 5 feedlots at a concentration less than 8%. 

Sampling occurred at each feedlot on four occasions at ∼6-week
intervals. At each feedlot visit, 4 pens of cattle within 3 weeks of
slaughter were selected and 24 freshly voided fecal pats were sampled.

Ten-gram samples were enriched in 90 mL of modified tryptic soy broth with novobiocin (20 mg/L) for 14 h at 42°C. Enrichments were subjected to immunomagnetic separation, plating onto chromogenic agar with novobiocin (5 mg/L) and potassium tellurite (2.5 mg/L), incubation for 18 h at 37°C, and latex agglutination of morphologically typical colonies. E. coli O157 was recovered from 16.7% of 3840 samples.

Adjusted prevalence was 14.3% after controlling for within-feedlot and
within-pen clustering. Prevalence during each sampling period was
19.9% (round 1), 21.0% (round 2), 14.1% (round 3), and 11.7% (round
4). Prevalence varied between cohorts, but this difference varied over
time (p = 0.06). Among those with greater than 15% of the diet as DGs, prevalence was greater than those with less than 8% inclusion for all rounds of sampling (p < 0.01). Averaged across time, prevalence was 23.9% and 9.4% for those with greater than 15% and those with less than 8% of DGs, respectively. While observational, these data provide real-world support of reports of increased E. coli O157:H7 burden associated with DG use in cattle diets.

Corn-based distillers’ grains in diets for feedlot cattle are associated with the burden of Escherichia coli O157 in feces

Foodborne Pathogens and Disease 15:298-405

Evan Chaney, Rebecca Maloney, Bradley J. Johnson, J. Chance Brooks, Mindy M. Brashears, and Guy H. Loneragan.