The effects of a cow's diet on E. coli levels
Researchers from Kansas State University have concluded that feedlots containing cattle that are fed distiller's grain, a byproduct of ethanol production, have an increased incidence of E. coli O157:H7 - a toxic form of E. coli that causes human illness. T.G. Nagaraja, a professor of diagnostic medicine and pathobiology at Kansas State's College of Veterinary Medicine, and Jim Drouillard, a professor of animal sciences at Kansas State, conducted research to determine whether diet influences the number of bacteria in an animal's gut.
An Associated Press article regarding the new research focused on the need for further research now that the increase has been identified:
Research in the next few years will focus on finding out the reasons for the prevalence of the bacteria in cattle fed a distiller's grain diet. Nagaraja said it could be related to changes in the animal's gut from the diet. The byproduct may also provide a nutrient for the E. coli bacteria.Domer said more work needs to be done to see if the prevalence of E. coli contamination can be controlled by providing cattle that are fed distiller's grain with other feed sources.
"The research is still early and probably needs more work so we can know how to control the situation," Domer said.
Feeding cattle distiller's grain is a big economic advantage for ethanol plants," Nagaraja said. "We realize we can't tell cattle producers, 'Don't feed distiller's grain.' What we want to do is not only understand the reasons why 0157 increases, but also find a way to prevent that from happening."
E. coli O157:H7 bacteria is believed to mostly live in the intestines of cattle, but has also been found in the intestines of chickens, deer, sheep, and pigs. E. coli O157:H7 does not make the animals that carry it ill; the animals are merely the reservoir for the bacteria.
Meat typically becomes contaminated with E. coli O157:H7 during the slaughtering process, when the contents of an animal's intestines and feces are allowed to come into contact with the carcass. Unless the carcass is sanitized, the E. coli bacteria are eventually mixed into the meat as it is ground. Because the bacteria is mixed into the meat during the grinding process, and is not just on the surface, thorough cooking (to160 degrees) is required to prevent E. coli O157:H7 poisoning from consumption of ground beef. Contaminated meat looks and smells normal, and although the number of organisms required to cause an infection is not known, it is suspected to be very small.
A 2003 study on the prevalence of E. coli O157:H7 in livestock at 29 county and 3 large state agricultural fairs in the United States found that E. coli O157:H7 could be isolated from 13.8% of beef cattle, 5.9% of dairy cattle, 3.6% of pigs, 5.2% of sheep, and 2.8% of goats. Over seven percent of pest fly pools also tested positive for E. coli O157:H7.
