U.S. Agriculture Secretary Ann Veneman announced Tuesday so-called "downer" cattle -- sick or injured animals unable to walk on their own -- will be banned from human consumption as part of sweeping changes to the U.S. beef industry.

"Effective immediately the USDA will ban all downer cattle from the human food chain," Veneman told a Washington press conference.

That means animals tested for mad cow -- also know as bovine spongiform encephalopathy (BSE) -- will no longer be marked "inspected and passed" until there is confirmation they do not have the brain wasting disease, Veneman said.

Currently, the carcasses of cows being tested for mad cow can be processed while slaughter plants wait for test results.

Further restrictions aimed at increasing the safety of the U.S. beef supply include banning the use of head and spinal tissue -- such "specified risk materials" are believed to transmit BSE to humans.

An international panel of scientists will also be appointed to review the U.S. response to the country's first case of mad cow disease.

The experts will be charged with providing "an objective review of our response actions and areas for potential enhancement," Veneman said.

Some of the same experts that looked into a similar case of BSE found in Canada in May will sit on the panel.

Meanwhile, USDA Chief Veterinarian Ron DeHaven said his department expects to know within days the whereabouts of 81 cows which were part of the same herd as the Washington state animal infected with mad cow.

The USDA's investigation into where those animals are "will come to fruition in the next couple of days," DeHaven said.

The USDA maintains the cattle were imported from Canada in 2001 -- at the same time as the Holstein infected with mad cow.

Canadian officials were hedging Tuesday on the origins of the infected cow. Based on its ear tags and records kept by farmers in the U.S. and Canada, it's believed the animal was born in Alberta.

But, Agriculture Minister Bob Speller has yet to be convinced the cow came from Canada.

"We don't know, in fact. We haven't completed the investigation and I turn it over to the scientists to tell you how that investigation goes. But we don't even know if it's the right cow yet," he told reporters at an Edmonton press conference.

Still, U.S. officials are continuing to look to Canada as the source of the infected animal.

"As our technical experts have informed you, our main line of inquiry indicates that the cow slaughtered in Washington state and found to have BSE may have been born in Canada," Veneman said.

The ear tags have led investigators to a dairy farm near Leduc, Alberta, just southeast of Edmonton, George Luterbach, a veterinary official with the Canadian Food Inspection Agency, told reporters in Edmonton.

It's believed the infected cow was born there in April of 1997.

Officials from Canada and the U.S., in addition to an independent third party, will test DNA from the brain tissue of the infected cow. That sample will be compared to DNA from the sire of the Leduc cow.

Most of the Leduc farm's 82 adult cows were exported to the U.S. in 2001, but investigators have found about 20 younger animals stayed in Canada, Luterbach said.
The whereabouts of those animals are currently being traced.

"We have not quarantined any animals insofar as we have not confirmed that this case has come from Canada," Luterbach said.

The feed consumed by the herd is also being traced, he added.

Speller told CTV's Canada AM Tuesday that while it's important to identify where the infected cow originated, it's equally important to determine where the feed came from.

"We need to look at not only where the cow came from, but exactly where the feed that caused the cow to get BSE came from, whether it was fed to the cow in Canada or the United States," Speller said.

He also stressed that the latest case of mad cow should not come as a surprise.

"The international scientists that gave the peer review to Canada and gave us such glowing marks said at that time that we might find one or two more cases in North America," Speller said.

"That's no surprise to us, that's no surprise to any of the countries that have opened up their borders to Canada.
They knew this beforehand. They knew there very well may be other cases in North America."

Canada is the only country to issue a partial ban on American beef, limited to processed meats. About 30 other countries have closed their borders completely to U.S. beef and cattle. Speller says our decision was based on scientific fact -- not political motivation.