http://www.nytimes.com/2003/12/31/dining/31WELL.html?fta=yThe safest beef is from cattle that have been raised organically, because by law they cannot be fed animal byproducts, which, while banned from cattle feed since 1997, are believed to be the major source of mad cow disease. Organic beef is available by mail order, online and in some stores.
Beef that is labeled grass-fed, but not certified organic, would be a second choice. There are no regulations governing what can be called grass-fed, so it can be difficult to ascertain what the animal has eaten. Experts advise asking the butcher or supplier a few questions to assure the meat's safety.
• Has the animal's feed ever been supplemented with grain or with protein, which might include animal byproducts?
• Were the animals "finished" with any grain? In other words, were they fed grain to improve the flavor of the meat before slaughter?
• Were the calves weaned with a milk replacer? Milk replacer can contain cows' blood, which might spread the disease.
• Was the animal slaughtered and processed at the same place as conventional cattle? If so, what assurances are there that they are not contaminated?