Colorado State University study found that 80% of consumers in the Denver-Colorado area preferred the taste of United States corn-fed beef to Australian grass-fed beef, and negligible difference in taste preference compared to Canadian barley-fed beef, though the cattle's food was not the only difference in the beef tested, nor is Denver a representative sample of the world beef market, so the results are inconclusive. Remarkably, in some circumstances, cattle are fed wine or beer. It is believed that this improves the taste of the beef. This technique has been used both in Japan and France. Nutrition Animal products for human consumption from animals raised on pasture have shown nutritional differences from those of animals raised on other feedstuffs. Health E. coli Escherichia coli, although considered to be part of the normal gut flora for many mammals (including humans), has many strains. Strain E. coli 0157:H7 can cause foodborne illness. A study found that grass-fed animals have as much as eighty percent less E. coli in their guts than their grain-fed counterparts, though this reduction can be achieved by switching an animal to grass only a few days prior to slaughter. Also, the amount of E. coli they do have is much less likely to survive our first-line defense against infection: stomach acid. This is because feeding grain to cattle makes their normally pH-neutral digestive tract abnormally acidic; over time, the pathogenic E. coli becomes acid resistant. If humans ingest this acid-resistant E. coli via grain-feed beef, a large number of them may survive past the stomach, causing an infection. A study by the USDA Meat and Animal Research Center in Lincoln Nebraska (2000) has confirmed the Cornell research. Bovine spongiform encephalopathy Meat and bone meal can be a risk factor for bovine spongiform encephalopathy (BSE), when healthy animals consume tainted tissues from infected animals. People concerned about Creutzfeldt–Jakob disease (CJD), which is also a spongiform encephalopathy, may favor grass-fed cattle for this reason. In the United States, this risk is relatively low as feeding of protein sources from any ruminant to another ruminant has been banned since 1997. The problem becomes more complicated as other feedstuffs containing animal by-products are still allowed to be fed to other non-ruminants (chickens, cats, dogs, horses, pigs, etc.). Therefore, at a feed mill mixing feed for pigs, for instance, there is still the possibility of cross-contamination of feed going to cattle. Since only