Study finds DDG-E. coli link

By Jerry W. Kram | November 13, 2007
Web exclusive posted Dec. 7, 2007, at 1:27 p.m. CST

A study conducted by researchers at Kansas State University found that adding dried distillers grain to cattle rations increased the prevalence of E. coli O157 in cattle manure samples. E. coli O157 is a serotype of a bacteria normally found in the intestines. It produces a toxin that can cause severe health problems or death and have forced many recalls of meat products.

The study, which will be published in Applied Environmental Microbiology in January, examined 379 heifers fed one of three diets: steam flaked corn with 15 percent silage and either 0 percent or 25 percent DDGS or steam flaked corn with 5 percent silage and 25 percent DDGS. The prevalence of E. coli O157 varied greatly over the 12 week study, something that has been seen in other cattle feeding studies. However, the prevalence of the pathogen was higher in the two groups cattle fed the rations containing DDGS. Two concurrent studies described in the paper sampled fluid from the rumen and intestines of cattle and also found that E. coli O157 grew more vigorously in fluid collected from the cattle fed DDGS.

"This is a very interesting observation and is likely to have profound implications in food safety," said T.G. Nagaraja, professor of diagnostic medicine and pathobiology and one of the authors of the study.

The paper discussed two hypotheses to explain the increased prevalence of the pathogenic bacteria. One is that using distillers grains lowers the amount of starch and increases the amount of fiber in the cattle rations. That changes the environment of the cattle's digestive tract which allows the pathogen to gain a competitive advantage over other intestinal flora. Another hypothesis is that there is some component of distillers grains that promotes the growth of E. coli O157. There is some evidence supporting this idea from in vitro experiments.

The conclusions of the paper stated that the implications of these observations were very serious because of the increasing role of distillers grains in the cattle industry due to the rapid expansion of ethanol production. Beef producers and processors are unlikely to want a product that appears to increase the prevalence of E. coli O157. The paper concluded that it is important to learn why distillers grains have this effect so researchers can devise feeding strategies that do not compromise the perceived safety of beef products. "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 O157 increases, but also find a way to prevent that from happening."

Nagaraja said research in the next few years will focus on finding out why O157 is more prevalent in cattle fed a distiller's grain diet.