WASHINGTON (Reuters) - U.S. makers of pet food and all other animal feed will be prevented from using certain materials from cattle at the greatest risk for spreading mad cow disease under a rule that regulators finalized on Wednesday.

The U.S. Food and Drug Administration, which oversees animal feed, said excluding high-risk materials from cattle 30 months of age or older from all animal feed will prevent any accidental cross-contamination between ruminant feed (intended for animals such as cattle) and non-ruminant feed or feed ingredients.

The new rule takes effect in April, 2009.

Contamination could occur during manufacture, transport or through the accidental misfeeding of non-ruminant feed to ruminant animals.

Canada and the United States banned the inclusion of protein from cows and other ruminant animals such as goats and sheep in cattle feed in 1997, following a mad cow outbreak in Britain.

The measure issued today finalizes a proposed rule opened for public comment in October 2005. It goes into effect on April 23, 2009.

The major U.S. safeguards against mad cow disease are the feed ban, a prohibition against slaughtering most "downer" cattle -- animals too sick to walk on their own -- for human food, and a requirement for meatpackers to remove from carcasses the brains, spinal cords and other parts most likely to contain the malformed proteins blamed for the disease.

Mad cow disease is a fatal, brain-wasting disease believed to be spread by contaminated feed. People can contract a human version of the disease, know as Variant Creutzfeldt-Jakob Disease, or vCJD, which scientists believe can be spread by eating contaminated parts from an infected animal.

The United States has found three cases of mad cow disease, including the first one detected in December of 2003. Soon after, U.S. beef exports were virtually halted. U.S. official have been slowly working to resume beef shipments.

Last week, South Korea officially announced it would gradually open its market to U.S. beef imports as Washington intensifies safety standards.

Eventually, if all goes well, a full range of U.S. beef boneless and bone-in, from animals of any age, would be shipped to a market estimated to be worth up to $1 billion a year.

(Reporting by Christopher Doering; Editing by David Gregorio)

미국, 2009년부터 30개월이상 소, 사료로도 금지, 한국으로 수출하나 ?