WASHINGTON – After corn is processed to make ethanol, what's left of the corn is a byproduct known as wet distiller's grains with solubles (WDGS), which is sometimes used as a cattle feed ingredient. US Department of Agriculture scientists in Clay Center, Neb., are investigating the pros and cons of this practice.

James Wells, a microbiologist with USDA's Agricultural Research Service (ARS), said WDGS are rich in protein plus they provide calories and minerals. WDGS have been the subject of many studies by Wells and his colleagues at the ARS Roman L. Hruska US Meat Animal Research Center in Clay Center since 2007. Wells has led studies to investigate the relation between use of WDGS in feed and the incidence and persistence of Escherichia coli O157:H7 in cattle manure and on the animals' hides.

Cattle are a natural reservoir for E. coli. Although apparently harmless to cattle, the microbe can cause illness or death in humans. E. coli in manure can infect or reinfect animals in pastures and feedlots. And if E. coli appears on the animals' hides, it could contaminate meat and equipment at the packinghouse.

Wells and his Clay Center colleagues showed in early experiments with 608 steers the incidence and prevalence of E. coli O157:H7 in manure, and the incidence on hides, was significantly higher for cattle whose corn-based feed included 40 percent WDGS than those whose feed did not contain WDGS.

Wells and his Clay Center colleagues published some of these findings in a 2009 article in the Journal of Food Protection. The research was funded in part by the Beef Checkoff, a promotion and research program funded by US beef producers and importers.

The researchers want to determine what causes the difference in E. coli levels and what can be done to reduce them in follow-up studies.