The following is from Science Sept 11, 1998;281:1666-1668, 1578-1579: and shows the contamination levels of grain-fed cattle. Best, Peter ================================== Bovine digestive tracts and manure can harbor a variety of E.coli strains, including E. coli 0157:H7, which has been associated with potentially deadly infections in humans. When beef is slaughtered, it is often contaminated with cattle manure. Produce can also be contaminated with the bacteria if fertilized with manure. Despite more stringent food safety standards, E. coli, 0157:H7 outbreaks have become increasingly common since World War II. Since then, most farmers have been feeding their cattle grain, rather than less costly, less fattening hay. Cattle fed grain had 300 times as much E. coli in their feces as did cows fed hay, the researchers found. Moreover, the bacteria in the grain-fed cattle's feces were much more likely to survive after being soaked for an hour in acid. This is significant because human stomach acid usually kills pathogens that could otherwise cause infection. Why were the grain-fed cattle more likely to have acid-resistant bacteria in their feces? Cattle produce only small quantities of an enzyme that breaks down starch, the researchers explain. As a result, large quantities of starchy grain pass into cows' intestines undigested, and the starch ferments there, producing fatty acids. Bacteria "raised" in this acidic environment may become acid resistant, and can survive and multiply, if they later find their way into human stomachs. Switching cattle from a grain diet to a hay diet, however, quickly changes the intestinal environment and eliminates acid-resistant ED. colic in the digestive tract within 5 days, the researchers report.