Federal investigators increased to 81 the number of cattle now roaming the U.S. that may have been exposed to mad-cow disease, Tuesday's Wall Street Journal reported.

Yet even the 81 figure isn't complete. Many of these cattle presumably have given birth since entering the U.S., at least some of which came in a group thought to include the Washington state Holstein that was found last week to have been infected with bovine spongiform encephalopathy, otherwise known as BSE, or mad-cow disease. Previously, federal investigators said 73 dairy cattle had come into the U.S. in August 2001 from the same herd in Canada's Alberta provence that is thought to have been the original home of the infected Holstein.

Investigators hope to find and screen those cattle for BSE, which creates holes in the brains of infected cattle. By eating contaminated beef products, people can catch a similar form of the affliction, known as variant Creutzfeldt- Jakob disease.

The federal government's ability to quickly control the fallout from the nation's first case of mad-cow disease is being complicated by poor record keeping of cattle shipments and the inexperience of U.S. officials, who never have had to deal with a mad-cow discovery, agricultural experts say.

Indeed, a week into the federal government's search for the source of this mad-cow case, investigators have just managed to confirm the age of the infected cow at its slaughter -- 6 1/2 years -- which is crucial to figuring how long ago it might have been infected. The mad-cow disease can incubate silently for three to six years.

U.S. officials said Monday that investigators still aren't certain whether the infected cow came from Canada and have yet to recover the vast majority of meat from the sick animal, which was slaughtered Dec. 9 at a small Moses Lake, Wash., meatpacker. Meat from the cow was mixed with the meat of 19 other cattle killed at the plant that day and eventually shipped to more than 40 businesses in eight states and Guam. Officials believe most of the meat is in Oregon and Washington state.

The lack of hard information is hurting the U.S.'s ability to persuade about two dozen trade partners to lift the bans on U.S. beef that they imposed after the mad-cow finding. A U.S. trade delegation sent to Tokyo to reopen beef sales was immediately rebuffed Monday by Japanese officials, who said the U.S. government doesn't yet have the facts Japan needs to decide whether it is safe to drop the ban on U.S. beef imports.

Trade experts believe that many of the nations that have banned U.S. beef imports because of the mad-cow discovery won't make a move until they see what is done by Japan, which is the biggest importer of U.S. beef, spending roughly $ 1 billion annually.

Copyright 2003 Dow Jones & Company, Inc

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