Effect of Dietary Protein, Fiber, and Digesta Passage Rate on the Duration and Concentration of Escherichia coli 0157:H7 Shed by Cattle

Abstract

Infection with E. coli O157:H7 is the most common cause of human hemorrhagic colitis in North America. Cattle are a reservoir for this human pathogen and individual animals are sporadically and transiently colonized. We hypothesize that pre-harvest dietary management may reduce the risk of E. coli O157-positive animals entering our food chain. The effect of dietary energy, fiber, and digesta passage rates on the duration and concentration of fecal E. coli 0157 was determined. Sixteen healthy Charlais x Hereford or Holstein heifers were acclimated to one of four diets: a finishing diet (high in energy and low in fiber), a growing diet (low in energy and high in fiber), chopped alfalfa (small particle size), or long alfalfa (large particle size). A single oral dose of 1010 colony forming-units of E.coli 0157 was administered to each animal and fecal samples were cultured for the bacteria by selective-enrichment twice a week for the duration of the study. No significant difference in the shedding of 0157 by animals on the finishing or growing diet was observed. However, withholding feed of either type, for 24 hours, did increase the concentration of the bacteria in the fecal material of about half of the animals. A significant correlation (p value=0.008) was observed between digesta passage rate and the duration of fecal E. coli 0157. Animals with slower passage rates of 2 to 3 % per hour cleared E. coli 0157 from their intestinal tract in 10 days or less compared to animals with digesta passage rates of 4 to 5 % per hour who shed the bacteria for more than 69 days. These results show that cattle diet influences the duration and concentration of fecal E. coli O157:H7.