Over the years I have followed the grain fed issue as it relates to the prevalence of E. coli O157:H7 in cows guts and hides at slaughter. Frankly, the data has been mixed. A year ago I penned, “Has the nail been driven into the coffin of the conventional wisdom that grass-fed beef is safer than grain-fed beef?” It seemed at that point that the weight of the literature was finding no clear answer to the grain and E. coli O157:H7 connection. I therefore was interested in seeing the article by USDA ARS’s Marcia Wood that “Studies Focus on Feed Ingredient’s Effects on Levels of E. coli O157:H7 in Cattle.” Here is the article (with links) in full:
After corn is processed to make ethanol, what’s left of the corn looks something like slightly dampened cornmeal, though a somewhat darker yellow, and not as finely ground. Known as “wet distiller’s grains with solubles” (WDGS), this byproduct is sometimes used as a cattle feed ingredient. U.S. Department of Agriculture (USDA) scientists in Clay Center, Neb., are studying the pros and cons of that practice.
Since 2007, WDGS have been the subject of an array of studies by Wells and others at the ARS Roman L. Hruska U.S. Meat Animal Research Center in Clay Center.
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 the microbe. It is apparently harmless to them, but can cause illness in humans. E. coli in manure can newly infect or reinfect animals in pastures and feedlots; if E. coli ends up on the animals’ hides, it could subsequently contaminate meat and equipment at the packinghouse.
In early experiments with 608 steers, Wells and his colleagues at Clay Center showed that 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.
Wells, along with research leader Tommy L. Wheeler, food technologist Steven D. Shackelford, microbiologists Elaine D. Berry and Norasak Kalchayanand, and other colleagues at Clay Center 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 U.S. beef producers and importers.
In follow-up studies, the researches want to determine what causes the difference in E. coli levels, and what can be done to reduce them.
ARS is the USDA’s chief intramural scientific research agency. The Clay Center studies enhance food safety, a USDA top priority.