The panel, made up of experts from Britain, New Zealand, Switzerland and the United States, also recommended testing many more head of cattle, adopting rapid European tests and removing brains, spinal columns and intestines of all cattle older than 1 from food supplies.

Convened after the first cow infected with bovine spongiform encephalopathy in this country was found in December in Washington State, the panel released its report at a conference in Maryland. Its chairman, Dr. Ulrich Kihm, a Swiss veterinarian, said the United States "could have a case a month" of mad cow disease if it was doing enough testing, Reuters reported. Dr. Kihm made the estimate based on the experiences of European countries. But he did not predict an outbreak like the one in Britain, where hundreds of thousands of infected cows were found and more than 100 people died of a degenerative brain disease.

The chief veterinary officer for the Agriculture Department, Dr. Ron DeHaven, said that it was "no surprise that there may be other cases in North America," but that there was "no way to know whether there would be one a month or one every five years."

Even if there are more, Dr. DeHaven said, the panel acknowledged that the steps that the department took on Dec. 30 — banning the slaughter of sick and injured cows for human food, as well as the removal of brains, spinal cords and intestines from older cows at slaughter — are the most important to protect consumers. The department will respond to the report quickly, he said "because there is a sense of urgency about this."

Though the document, "Report on Measures Relating to Bovine Spongiform Encephalopathy in the United States," was couched in dry uncritical language, it made clear that the panel believed that the department had not done enough to protect consumers or find all the diseased cows in North America. It also said blanket assurances that "beef is safe" could undermine regulatory efforts.

"It's explosive stuff," Michael Hansen, an expert on mad cow disease at Consumers Union, said. "It's an implicit admission that the critics have been correct and B.S.E. has been here all along."

Dr. Gary Weber, executive director for regulatory affairs at the National Cattlemen's Beef Association, said the report was "not objective" and was "negative in tone." Dr. Weber called Dr. Kihm's remarks "more soothsayer than scientist."

European scientists "don't want to believe that the North American risk situation is different from Europe's," he said. One panel member whom Dr. Weber declined to name had privately told him that an earlier draft had been even more damning but that the member had been "able to moderate it."

It has been illegal since 1997 to feed meal made from ruminants like cows, sheep, goats and deer to other ruminants. It is legal to feed hogs and chickens. Partly because it has been so hard to prevent cross-contamination in rendering plants and the trucks that carry the dried meal, the panel recommended that cattle be given no more animal feed.

The department tests 40,000 head of the more than 30 million head of cattle slaughtered each year. Dr. DeHaven said it was possible that the agency would consider more aggressive tests and that the results would determine whether cattle as young as 1 needed to be treated if they could be infected.

Although testing all slaughtered cattle is "unjustified in terms of protecting animal and human health," the panel said, it recommended testing all cattle older than 30 months that die on farms, that collapse from illness or injury or that show the twitching, nervousness or aggressiveness symptomatic of mad cow disease. In addition, the panel suggested randomly testing healthy cattle.

Switzerland randomly tests 3 percent of healthy cattle at slaughter.

Decisions about what animals go into cattle feed are made by the Food and Drug Administration, which last week banned feeding cow blood, chicken waste and restaurant scraps to cattle, but continued with rendered hogs and chickens. Industry critics objected, saying hogs and chickens eat rendered cattle, so the disease could pass through.