Study: Cattle Diet May Help E. Coli
Sep. 10, 1998
WASHINGTON (AP) _ Scientists have discovered a simple way to dramatically reduce the risk of people getting sick from E. coli-tainted beef: Change what cattle eat for a few days before they're slaughtered.
Feeding cows grain, as most farmers do to fatten them up, encourages the growth of E. coli bacteria that are strong enough to sicken humans, according to new Agriculture Department studies conducted at Cornell University.
But feeding cows hay instead of grain for a mere five days before they're slaughtered could virtually eliminate that risk, said USDA microbiologist James Russell, who did the study while stationed at Cornell.
``It's a way of attacking the problem long before the animal reaches the slaughterhouse, the meat reaches the supermarket or the meat is prepared by the consumer,'' Russell said. ``We're very hopeful'' the result will be far fewer sick Americans.
The study, in Friday's edition of the journal Science, is generating excitement among food-safety experts.
``This looks to be a relatively inexpensive, potentially important intervention that farmers can do,'' said Robert Buchanan of the Food and Drug Administration, lead scientist for the Clinton administration's food safety initiative.
And it would save farmers money. ``Hay is a lot cheaper than oats,'' Buchanan noted.
The beef industry welcomed the news.
``We think it's a major breakthrough,'' said Gary Cowman, quality assurance chief for the National Cattlemen's Beef Association. ``It's something very, very practical.''
But there are still questions to be answered, he cautioned, including whether abruptly changing a cow's diet from starchy grain to fibrous hay overnight would cause digestive problems. Cowman said more research should settle those concerns within a year.
E. coli is a common bacterium that lives in the digestive tracts of humans and animals. Some E. coli strains sicken people; one strain _ E. coli O157 _ is highly toxic, causing bloody diarrhea and severe cramps and sometimes even kidney damage or death.
The Centers for Disease Control and Prevention estimate E. coli 0157 sickens up to 20,000 Americans each year, killing several hundred.
E. coli can get into beef during slaughter, from contamination with cattle feces. Thorough cooking, especially of hamburger, kills E. coli, but outbreaks from undercooked meat or poor kitchen sanitation increasingly make headlines. Just last year, E. coli prompted the nation's largest meat recall _ 25 million pounds of ground beef.
Its ability to sicken depends on whether it is strong enough to survive the typical two hours that a person's meal sloshes around in the stomach's highly acidic juices. If so, the bacteria move down to infect the person's intestines.
Feeding cows grain _ common since World War II because it fattens cattle quicker so the beef is more tender _ increases acidity in the cows' colons, where E. coli lurks. But no one had studied whether this cattle diet change let E. coli adapt to acidic conditions so it would pass unharmed through a human stomach.
First, Russell took fecal samples from Cornell cows on different diets. Those fed more grain had more E. coli in their feces. In laboratory tests, those bacteria were less likely to be killed by stomach acid.
Next, he controlled the cows' diet. Cattle switched to a grain-based diet typical of commercial feedlots had a 1 million-fold increase in acid-resistant E. coli in their feces, Russell said.
Because of differences in how cows digest starchy grains vs. roughage like hay, a hay diet doesn't increase their acid levels. Thus, Russell found that cows fed hay had E. coli that was easily destroyed in an acid bath similar to the human stomach.
None of Cornell's cows actually harbored the super-toxic E. coli O157, just milder strains. So Russell tested that superbug in the laboratory, and found that E. coli O157 becomes resistant to stomach acid just like other E. coli strains. But to be sure, FDA's Buchanan cautions that the hay diet should be tested in cows actually infected with the super-bacteria.