OLYMPIA, Wash. (AP) -- A slaughterhouse worker who claims to have killed the first U.S. cow to test positive for mad cow disease said the animal wasn't a so-called "downer" cow, an assertion disputed by federal agriculture inspectors.

"She was a walker," David Louthan said after speaking Tuesday before the state House and Senate agriculture committees. He said he killed the cow because it was acting wild.

Louthan insists the cow could walk on its own and wouldn't have been tested had he not killed it outside the slaughterhouse, which triggers automatic mad cow testing under a plant policy.

Louthan said he shot the animal outdoors because he feared it would trample other cows. "It got caught because I was in a hurry," Louthan said, calling the test "a fluke."

The infected cow was slaughtered at Vern's Moses Lake Meat Co. in Moses Lake, about 70 miles northeast of Mabton, on Dec. 9. Louthan claims he was laid off from the company two weeks after killing the cow, after he told television crews that the cow had already been eaten.

One day after the Dec. 23 announcement that the cow had tested positive for mad cow disease, USDA officials said the animal was a so-called "downer" -- an animal too sick or weak to walk by itself.

Testing for mad cow disease in the United States has been limited to downer cows.

USDA spokesman Steven Cohen said the cow had been injured during calving and was lying down when an inspector checked it at the slaughterhouse.

"In the opinion of the veterinarian that examined the animal, that was a nonambulatory animal," Cohen said. That conclusion -- that the cow was a "downer" -- prompted the testing for mad cow disease.

Cohen was unsure whether Louthan indeed killed the cow in question. No one answered the telephone at Vern's Moses Lake Meat Co. on Tuesday and Louthan's claims could not be confirmed.

Mad cow disease, or bovine spongiform encephalopathy, eats holes in the brains of cattle and is incurable. The disease is a public health concern because humans can develop a brain-wasting illness, variant Creutzfeldt-Jakob disease, from consuming contaminated beef products.

Since the case was discovered, agriculture officials have killed more than 700 cows in Washington, Oregon and Idaho. Although the cow was traced to a Canadian herd, more than 35 countries including Japan, Mexico and Korea have banned imports of American beef.

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