Early results of tests by the USDA’s Agriculture Research Service (ARS) indicate that E. coli O157:H7 in cattle manure, and on cattle hides, may be more prevalent for cattle whose corn-based feed contains what’s known as “wet distiller’s grains with solubles,” or WDGS.


As reported Thursday by Marcia Wood of ARS, the finding — from early experiments with 608 steers — adds more information to the debate over whether beef from grass-fed animals is safer than beef from grain-finished animals. 

Distiller’s grains, as Wood explains, are what’s left after corn is processed to make ethanol. One use for the byproduct is in cattle feed, particularly in the so-called “finishing phase” —  the last few months before slaughter. WDGS has been touted as a less expensive alternative to traditional feed ingredients, replacing additives such as corn, soybean meal, urea or mineral supplements.

For four years, ARS has been studying the pros and cons of using WDGS in cattle feed, including investigating its relation to E. coli O157:H7.    

Both pastured and feedlot cattle can harbor the microbe, which has no affect on them but can make humans sick. The pathogen is shed in manure and, if it gets on hides, can contaminate meat and equipment at slaughter and beyond. The more bacteria in the manure, the greater the risk of potential contamination.

Wood reports that ARS microbiologist James Wells and his colleagues at the U.S. Meat Animal Research Center in Clay Center, Nebraska, found that in the 608 steers they studied, “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 include WDGS.”

Some of the ARS findings on WDGS have already been published in a 2009 article in the Journal of Food Protection.  Wood said the researchers want to determine in folllow-up studies what causes the difference in E. coli levels, and what can be done to reduce them.

Last year, research reported in Foodborne Pathogens and Disease, called into question the conventional wisdom that meat from grass-fed cows is safer than meat from grain-fed cows.

That study found no differences in the percentages of E. coli isolates between the two groups. Those researchers concluded that there are no clear food safety advantages to grass-fed beef products over conventional beef products.


Photo by Stephen Ausmus for the ARS of the U.S. Meat Animal Research Center in Clay Center, Nebraska