The dispute over Canadian cattle imports has pitted US ranchers -- whose profits have improved slightly without competition from the North -- against feedlots and packers that have fewer cows to feed and slaughter without Canadian supplies.

The US Department of Agriculture said late Thursday that within days it will reopen the border to Canadian cattle, which were banned in May 2003 after a cow in Alberta was found to have mad cow disease.

"Because the ruling is effective immediately, we are immediately taking steps to resume the importation of cattle under 30 months of age," said Mike Johanns, agriculture secretary. He said the government is already working with Canadian food inspectors "to certify cattle for shipment."

The unanimous decision Thursday by a three-judge panel of the 9th US Circuit Court of Appeals overturned a Montana judge who blocked the USDA from reopening the border in March because he said it "subjects the entire US beef industry to potentially catastrophic damages" and "presents a genuine risk of death for US consumers."

The decision came a day after the Justice Department urged the appeals court in Seattle to reopen the border to imports. Justice Department attorney Mark Stern said lifting the ban is based on "good science" and would not result in the "infestation in American livestock."

During the hearing, the three justices suggested that US District Judge Richard F. Cebull perhaps should have given deference to the USDA's decision.

Judge A. Wallace Tashima said the law "does invest the secretary of agriculture with a certain amount of discretion." Judge Connie Callahan agreed, saying the USDA is "entitled to some deference. It's their whole job to keep up with the science to make those decisions."

The dispute has pitted ranchers -- whose profits have improved slightly without Canadian competition -- against feedlots and packers that have fewer cows to feed and slaughter without Canadian supplies.

"This is a tremendous victory for the northwest beef industry," said Cody Easterday, who runs an 18,000-head feedlot in Pasco, Wash. "It's basically going to protect our future for many families that depend on the beef industry for their livelihood."

American Meat Institute president J. Patrick Boyle said the ruling is also a victory for American consumers who were paying $1.85 a pound for ground beef before the border closed and are paying about $2.55 today.

Bill Bullard, executive director of the Ranchers Cattlemen Action Legal Fund, which brought the suit on behalf of US ranchers, said the decision imperils US beef.

"USDA did not provide significant justification for overturning a long-standing policy that protected both the US cattle herd and US consumers from the introduction" of mad cow disease, he said.

Judge Cebull issued his order blocking the importation of cattle months before a scheduled trial which pits the cattlemen's science against the USDA's. A trial on those competing views is scheduled July 27 before Cebull.

But with Thursday's decision, the appeals panel is not likely to allow Cebull to issue another injunction.

Mad cow disease is the common name for bovine spongiform encephalopathy, or BSE. People who eat meat tainted with BSE can contract a degenerative, fatal brain disorder called variant Creutzfeldt-Jakob disease, or vCJD. More than 150 people died from it following a 1986 outbreak in the United Kingdom.