K-State: Too soon to tell about E. coli, DDGs

By Jerry W. Kram | January 10, 2008
More research is needed before reaching any conclusions about the impact of distillers dried grains (DDGs) on E. coli O157 in cattle, according to researchers at Kansas State University.

Research by T.G. Nagaraja, a professor of microbiology, and Jim Drouillard, professor of animal science, found that feeding beef cattle a diet that included 25 percent DDGs increased the prevalence of the pathogenic strain of E. coli in the animals' manure. The announcement caused a storm of publicity over the increased use of DDGs produced by the growing ethanol industry. However, Nagaraja said it was too soon to rush to conclusions about the food safety implications of DDGs. "We'll need to look at the entire body of evidence before we can make any recommendations," Drouillard said, noting that many other universities are working on similar studies.

The KSU researchers said there is no evidence to suggest that the growth in the use of DDGs has anything to do with a recent uptick in the number of meat product recalls related to E. coli O157. "It is 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." Drouillard said it is also important that people know that DDGs don't carry E. coli.

The KSU results contrasted similar studies at the University of Nebraska, which found that DDGs had no impact on cattle shedding E. coli in manure. Terry Klopfenstein, a Nebraska professor of ruminant nutrition, said this wasn't surprising because many studies of the effect of livestock diet on E. coli O157 have produced inconsistent results. "It is kind of the nature of research with E. coli O157," he said. "It's just inconsistent. That isn't a criticism of the Kansas State work. It's just that I think within their research and within ours, there is a lack of consistency."

Klopfenstein said studies have shown that barley and steamed grain flakes also increase E. coli shedding in cattle, and he doesn't understand why. His study of DDGs provided variable results. "At the 20 [percent] and 30 percent levels of feeding, which would have been similar to [the KSU studies,] we actually saw a reduction in shedding of E. coli," Klopfenstein said. "When we went to higher levels, it picked up again. That's part of the inconsistency in our work. At some levels, it made it better, and at other levels, it didn't. So it's hard to evaluate that."

Work is being conducted at the two universities and elsewhere to develop a vaccine for cattle against E. coli O157. If successful, it would help livestock producers manage the pathogen and make the U.S. beef supply safer. Nagaraja said the vaccine work at KSU has produced some encouraging results. "One of the things that has been consistent between Kansas State and our work is that the vaccine has been helpful," Klopfenstein said. "It would be very helpful if we could get those on the market. We're more interested in doing things that are good interventions than we are trying to figure out the difference of different feeds."