Scientists at Kansas State University who are studying the effect of feeding distiller's grains to beef cattle said that more research is needed before cattle feeders and the public should reach definitive conclusions.
In three separate studies conducted over the last two years, T.G. Nagaraja, a professor of microbiology in K-State's College of Veterinary Medicine, and Jim Drouillard, K-State professor of animal sciences and industry, found that feeding beef cattle a diet that included 25 percent distiller's grains increased the prevalence (number of cattle positive) of E. coli 0157 in those animals' manure.
"In cattle, our previous research has shown that the hind gut -- which consists of the cecum, colon, and rectum -- is the site of persistence of E. coli O157," Nagaraja said. "Cattle feed passes through the rumen before it reaches the hind gut. We can't yet make any recommendations to the cattle industry with regard to our findings."
"We'll need to look at the entire body of evidence before we can make any recommendations," Drouillard said, noting that other universities also are studying this issue and that the research is far from finished.
Distiller's grains are a byproduct of the ethanol production process. A surge in ethanol production in recent years has led to increased availability of wet and dry distiller's grains, which have become a common ingredient in livestock and poultry rations.
"It's important for people to know that not all cattle have E. coli O157," Nagaraja said. "In fact, usually a relatively small percentage of cattle carry detectable levels of this organism in their manure."
"It's also important for people to know that distiller's grains do not contain E. coli," Drouillard said.
In the first of the three K-State studies, wet distiller's grain was fed to the test group of cattle. In the second and third studies, dry distiller's grains were fed. In all three studies, the cattle fed DGs all had increased prevalence of E. coli O157 – approximately a two-fold increase.
Numerous questions remain to be answered in future studies, including the effect lesser amounts of DGs would have on E. coli in cattle rations.
"Is there a component in the product that sets up the growth of E. coli 0157?" Nagaraja said. "That's something else that needs to be determined."
The researchers said that there is no evidence to suggest that a recent increase in the number of meat recalls related to E. coli 0157 has any connection to the practice of feeding distiller's grains.