INTERVENTIONS TO REDUCE FOODBORNE PATHOGENS IN SWINE AND CATTLE
Location: Food and Feed Safety Research
Title: Diet, Escherichia coli O157:H7, and cattle: A review after 10 years
Submitted to: Current Issues in Intestinal Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 12, 2008
Publication Date: February 1, 2009
Citation: Callaway, T.R., Carr, M.A., Edrington, T.S., Anderson, R.C., Nisbet, D.J. 2009. Diet, Escherichia coli O157:H7, and cattle: A review after 10 years. Current Issues in Intestinal Microbiology. 11:67-80.
Interpretive Summary: Escherichia coli are commonly found in the gut of cattle and can include E. coli O157:H7 and other foodborne pathogenic bacteria. Research has shown that cattle fed high-grain rations contain higher E. coli populations than do cattle fed a forage-based diet. Further studies have demonstrated a linkage between tannin and phenolic compounds found in forages and E. coli populations. Collectively results indicated that diet can impact populations of E. coli in th,e feces of cattle and can impact the dangerous E. coli such as O157:H7 and other Enterohemorrhagic E. coli (EHEC).
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 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. Researchers have repeatedly demonstrated that populations of total E. coli were higher in grain-fed than in forage-fed cattle. However, when cattle were abruptly switched from a high-grain diet to an all-hay diet, total E. coli populations declined 1000-fold within 5 days 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 demonstrated that diet does affect E. coli O157:H7 populations, but effects have been varied in magnitude and impact. Rapidly, ruminally fermented grains such as barley have been shown to increase the shedding of E. coli O157:H7, and feeding distillers grains can significantly increase fecal shedding of E. coli O157:H7. Further studies have indicated that the impact of forage feeding on reducing 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.