Diet, Escherichia coli 0157:H7, and cattle, a review after 10 years

Authors: Callaway, Todd; CARR, MANDY - NCBA; Edrington, Thomas; Anderson, Robin; Nisbet, David

Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/2009
Publication Date: 4/15/2009
Citation: Callaway, T.R., Carr, M.A., Edrington, T.S., Anderson, R.C., Nisbet, D.J. 2009. Diet, Escherichia coli 0157:H7, and cattle, a review after 10 years. Foodborne Pathogens and Disease. 6:67-80.

Interpretive Summary: Ruminant animals are reservoirs of the pathogenic bacteria E. coli O157:H7 and approximately 30% of feedlot cattle shed E. coli O157:H7. Feedlot and high-producing dairy cattle are fed high grain rations in order to increase feed efficiency. When cattle are fed high grain rations, some starch escapes ruminal microbial degradation and passes to the hindgut where it is fermented by bacteria. Researchers have repeatedly demonstrated that populations of total E. coli were higher in grain-fed than in forage-fed cattle. When cattle were abruptly switched from a high grain diet to an all hay diet, total E. coli populations declined 1000-fold within 5 d. This research provoked many questions about the effects of diet on E. coli O157:H7 populations that have not been conclusively answered after 10 years. Subsequent studies showed that diet does affect E. coli O157:H7, but effects have been varied in magnitude and impact. Rapidly ruminally fermented grain, such as barley, have been shown to increase the shedding of E. coli O157:H7, and distillers grains can significantly increase fecal shedding of E. coli O157:H7. Further studies have indicated that the impact of forage feeding on E. coli O157:H7 populations may be based upon concentrations of tannins and phenolic acids in forages. Data from researchers across North America indicate that diet does impact STEC/EHEC populations in cattle prior to slaughter. However, the economic, logistic, and practical impacts of dietary changes must be examined and accounted for.

Technical Abstract: Escherichia coli are commensal bacteria that can account for up to 1% of the bacterial population of the gut. Ruminant animals are reservoirs of the pathogenic bacteria E. coli strain O157:H7 and approximately 30% of feedlot cattle shed E. coli O157:H7. Feedlot and high-producing dairy cattle are fed high grain rations in order to increase feed efficiency. When cattle are fed high grain rations, some starch escapes ruminal microbial degradation and passes to the hindgut where it undergoes fermentation. Ten years ago, researchers demonstrated that populations of total E. coli were higher in grain-fed than in forage-fed cattle, and when cattle were abruptly switched from a high grain diet to an all hay diet, total E. coli populations declined 1000-fold within 5 d and reduced the ability of the surviving E. coli to survive an acid shock mimicking passage through the human gastric stomach. This research provoked many questions about the effects of diet or E. coli O157:H7 populations that have not been conclusively answered to date. Subsequent research has shown that diet does affect E. coli O157:H7 populations, but the effects have varied in magnitude and impact. Further studies have demonstrated that the effects of forage feeding on E. coli O157:H7 populations may be due to concentrations of tannins and phenolic acids in forages. Other ration components, such as rapidly ruminally fermented grains (e.g., barley), increase the shedding of E. coli O157:H7, and in some situations, feeding distillers grains can increase fecal shedding of E. coli O157:H7 due to VFA concentrations. Data from researchers across North America indicate that diet does impact STEC/EHEC populations in cattle prior to slaughter. However the economic, logistic, and practical impacts of dietary changes must be examined and accounted for.