uring a House debate last summer over a possible ban on using sick and injured cows for meat, Representative Gary L. Ackerman, a Democrat from New York, held up a photo of a crippled cow and cautioned that such "downer animals" carried the highest risk for mad cow disease.
A side of government-approved beef. The first case of mad cow disease in the United States has caused officials to rethink safety procedures.
But Representative Charles W. Stenholm, a powerful Texas Democrat and a rancher, countered that the government's screening program was tight enough to prevent any problems.
"The picture the gentleman is showing, that sick animal, will never find its way into the food chain," Mr. Stenholm said. "Period."
But now that a downer cow has the first confirmed case of mad cow disease in the United States, critics are assailing the beef industry and federal regulators for not taking greater precautions since the disease exploded overseas in the mid-1980's.
Though some scientists had long warned that mad cow disease would eventually appear in the United States, cattle owners and meatpackers repeatedly resisted calls for a more substantial program to test for the disease, and the Agriculture Department went along with them. Congress came close three times to banning the sale of meat from downer cows — ones that are too sick or hurt to amble into slaughterhouses — only to see the industry's allies block each of the bills at the last moment. And proposals for systems to track which farms produced sickened cattle — now required in Europe, Canada and Japan — also languished for years here.
"This is one of these times when unrealistic optimism triumphed over responsibility to the public," said Carol Tucker Foreman, a consumer advocate who ran the Agriculture Department's food-safety programs in the Carter administration.
If a number of countries stick with hastily announced plans to ban American beef, she added, "I think the damage to the American meat industry costs infinitely more than anything U.S. cattlemen would have had to pay to do this thing right."
Each year at least 200,000 cattle — and perhaps many more — are downers, and some of these animals could have mad cow disease, or bovine spongiform encephalopathy, which can destroy an animal's brain and central nervous system and lead to similar ailments in humans who eat diseased meat.
That is only a small fraction of the 104 million cattle in the United States and the 35 million slaughtered each year, suggesting that the industry may have taken a disproportionate risk in continuing to sell meat from the downers.
Government officials and packinghouse executives are now rethinking their positions and promising at least to consider many of the proposed changes they once rejected. They still say it did not make sense to do more earlier, given how expensive it would have been to guard against a disease that was not yet visible.
Many industry and government officials say they also believe that the disease and the damage from it can be contained, and that view was bolstered yesterday by the news that the Holstein cow that had the disease in Washington State was imported from Canada. The cow, which was slaughtered on Dec. 9, had not shown any signs of mad cow disease, but was considered a downer because it had been injured in giving birth to a large calf. The first North American case of mad cow disease was discovered last May in a downer cow in Wanham, Alberta.
"We're looking at what Europe is doing, what Canada is doing," Alisa Harrison, the press secretary for Agriculture Secretary Ann M. Veneman, said in an interview Friday. "Yes, we're looking at the whole system, we're looking at all options."
But a close look at how the crisis developed also reveals broader problems that could complicate efforts to restore consumer confidence and to ensure that no other tainted meat enters the food supply.
The nation's meat inspection system has undergone sweeping changes, with the government shifting much of the responsibility for safety to meat companies.
Beef production has also become increasingly concentrated and industrialized. Many packing plants now use advanced systems to extract more meat close to the animals' bones and spinal cords, increasing the chances that possibly risky tissue from their central nervous systems could end up in hamburgers and other processed meat.
And some scientists question whether government officials, even now, appreciate the full extent of the dangers. In some ways, the Agriculture Department still "believes its own propaganda," said Dr. Stanley Prusiner, a Nobel Prize-winning neurologist at the University of California in San Francisco and an authority on these types of diseases.
In Britain, more than 4.5 million animals have been killed since the disease was discovered in 1986. A related brain-wasting disease has killed 137 people, mostly in Britain.
The United States banned imports of live British cattle, and in 1997, the Food and Drug Administration, which oversees what animals eat, drafted a regulation: no more feeding bits of cows and other ruminants back to cows.
But critics say the regulation leaves glaring loopholes. Rendered cattle can be fed to pigs and chickens, which can then be fed back to cows. Cow blood, which cannot be guaranteed free of disease, is widely fed to calves as a "milk replacer." Deer that may be infected with disease can be rendered into cattle feed. Enforcement of the regulation, they say, has been lax.
Dr. Stephen Sundlof, an F.D.A. veterinarian, said that "with any new rule there is a period of time that compliance is not 100 percent — and then it gets better."
But Dr. Prusiner said the cow, whether born in the United States or Canada, "probably didn't get sick by eating anything."
He said regulators in both countries believed that mad cow illness was akin to a viral disease that "comes from the outside" and can be stopped by putting animals into quarantine. But given his suspicions that mad cow disease is endemic in both countries in low levels, it is more likely that the one or both cows had a spontaneous homegrown form of the disease and not the British version. He also said that using cow blood as a milk replacer is "a really stupid idea."
Food-safety experts said that slaughter and meatpacking procedures also may have to change.
Several major restaurant chains — including McDonald's, Wendy's and Burger King — have long refused to serve meat from downer animals to avoid health problems.
But powerful lobbies representing big ranchers and dairy farmers have stopped efforts in Congress in each of the last three years to prohibit slaughtering these animals for meat sold elsewhere.
Chandler Keyes, the Washington lobbyist for the National Cattlemen's Beef Association, said that because some downer animals merely have injuries like broken legs, his group would continue to resist efforts to declare all downer animals unfit for human consumption. That is a decision, he said, that is best left to federal veterinarians who inspect cows as they enter the nation's slaughterhouses.
But trusting federal veterinarians to find mad cow disease may be a mistake, an inspector at a Midwest meatpacking firm said. The inspector said that in his two years overseeing the killing of 600 downer cows, the veterinarian at his plant tested the central nervous tissue of only one of the animals. "All we tested downer cows for was antibiotic residue," said the inspector, who insisted on anonymity to protect his job.
Wayne Pacelle, the chief lobbyist for the Humane Society of the United States, said the economic devastation wrought by the nation's first confirmed case of mad cow disease was already changing the minds of some politicians who previously had been unmoved by arguments about public health and animal husbandry.
"Now the public realizes there is no firewall between B.S.E. and the American consumer," Mr. Pacelle said.
Last year, the Agriculture Department tested processed products from plants that use advanced meat recovery systems, which are meant to strip the last bits of meat from close to an animal's bone and spinal column, and found that 35 percent of the meat tested positive for central nervous system tissue.
Caroline Smith DeWaal of the Center for Science in the Public Interest, a consumer group, said the Agriculture Department still considered the presence of such tissue in meat to be more a labeling than a safety issue. Felicia Nestor, the food safety director at the Government Accountability Project, another advocacy group, added that given the possible dangers of eating such tissues, "it's just unacceptable that the American public should be put in this position."
Computerized systems for tracing food have also grown overseas. Outbreaks can be blocked early if an animal's history can be quickly obtained.
After waging their own battles with mad cow disease, Europe, Canada and Japan instituted government-regulated mandatory systems to trace animals from their birth to the grocery. They also require extensive testing of cattle herds, not the small risk assessment used in the United States that tests 20,000 to 30,000 cows or about 0.03 percent of the herds.
The United States does not require or have such records. But Agriculture Department officials said they would now speed up a project to create a national database for tracing animals. The system would be voluntary; farmers and ranchers could decide whether to register their animals in the data bank.
"At some point this could become mandatory," Ms. Harrison said.
In an industrialized agriculture system like the United States, where animals can be shipped thousands of miles in the course of being birthed, fed, slaughtered and packaged, the possibility of an uncontrolled outbreak has increased exponentially, the officials say.
"We need to be able to instantaneously track the history of a sick animal," said Mr. Stenholm, the Texas lawmaker, who also said he was ready to work on ways to keep sick animals out of the food system.
Dr. Prusiner and others say the only hope is better testing. Neither the United States nor Canada has ever carried out surveillance efforts beyond testing small numbers of downer cows, based on the notion that if mad cow disease were to appear, it would most likely show up in older animals showing signs of illness. By contrast, Western European countries tested 10 million cows last year, and Japan tested each of the 1.2 million cows it slaughtered.
Some experts say advances in the tests making them cheaper and quicker to conduct could make it easier to expand their use here and provide an answer to the crisis.
Representative Rosa DeLauro, Democrat of Connecticut and cochairwoman of the House Food Safety Caucus, said, "In this new age, where most cattle in the United States don't eat grass in open pastures, where they're crammed into feedlots most of their lives, and where we don't know where our meat comes from, I think it's time we take our safety precautions into the modern era."