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Changing the Diet of Cattle May Make Beef Safer!

© Neal Rolfe Chamberlain

About 30 million people in the United States suffer from food poisoning each year. Hamburger, fruit juices and even our vegetables have been sources of these nasty diarrheas. A large number of these food poisonings are due to Escherichia coli. Escherichia coli is a normal inhabitant in our intestines however some strains of this organism can cause serious illness. One example is the notorious Escherichia coli O157:H7 that can cause very serious illness in children and the elderly.

Cattle also have Escherichia col in their intestines. Some of the Escherichia coli in these cattle can cause food poisoning. It is next to impossible to prevent all fecal contamination of meat at the slaughterhouse. Some fecal matter can get on the surface of the meat. When it is ground up to make hamburger the bacteria then get spread throughout the meat. Very few disease-causing Escherichia coli are needed to cause illness in humans. As few as 10 bacterial cells can cause illness in humans.

Disease-causing Escherichia coli strains have several common abilities. One of those abilities is to produce the right toxins that will cause damage to the intestines resulting in diarrhea. Another important ability is the bacteria's ablity to survive in an acidic environment. To cause an intestinal infection the bacteria must get past the stomach. The stomach is a very acidic place. Few bacteria survive in this environment. If an Escherichia coli is treated just right in a laboratory you can get bacteria that are highly resistant to acid treatment.

Recently, a group of scientists reported in Science (Sept. 11, 1998; Vol. 281 pg. 1666-1668; Grain Feeding and the Dissemination of Acid-Resistant Escherichia coli from Cattle) that by changing the diet of cattle they could lower the numbers of Escherichia coli in the intestines of their cattle. Since World War II cattle have been fattened using large amounts of grain. Grain has lots of starch in it and cow's stomachs are not very good at breaking down these starches. When the starch gets in the intestine the Escherichia coli dwelling there have a feast. They can breakdown the starch and when they do they produce acid. Since the bacteria find it easy to breakdown the starch they will increase in numbers. This increase in acid production also causes an acidic environment to occur in the intestine. This acidic environment induces the production of many acid-resistant Escherichia coli.

Hay on the other hand does not contain much starch. The intestine of the cow does not become as acidic and the Escherichia coli turn out to be less resistant to acid treatment. That is the theory anyway. Recently, a group of researchers at the Division of Biological Sciences

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