The cow heads come plastic-wrapped in cardboard boxes from nervous ranchers and dairy farmers, shuttled by speedy courier to a red-roofed building on the northeastern edge of the UC Davis campus.

There, behind heavy security doors labeled "BIO HAZARD," animal pathologists in blue surgical scrubs dissect the bloody cargo on stainless steel tables that look as though they came off the set of the television show "CSI." The pathologists' mission: find the telltale "Swiss cheese" holes that form in the brain stems of cows with the rare malady that's been in the national spotlight -- mad cow disease.

The state Department of Food and Agriculture lab at the University of California, Davis, is one of a dozen U.S. facilities that are part of the national detection system for bovine spongiform encephalopathy. The pathologists, who work for the Davis-based California Animal Health and Food Safety Laboratory System, see an average of one suspicious cow case every 10 days.

After an initial diagnosis, they send suspect cow parts to a federal laboratory in Ames, Iowa, for further examination.

"I wouldn't be surprised if we're asked to do more in the way of (mad cow) testing," said CAHFS Director Alex Ardans. "Ireland tests 5,000 to 8,000 head every day. We could do the same in this country. It would take different technology, but it could be done."

Currently, U.S. Department of Agriculture policy limits definitive mad cow testing to its Iowa facility, where the process can take up to two weeks.

Critics, including U.S. Sen. Barbara Boxer, D-Calif., blasted the USDA last month for taking 13 days to confirm that a Washington dairy cow had mad cow disease, during which time its meat was processed and distributed to stores and restaurants, including some in the Sacramento area.

This week, Boxer tried to ramp up political pressure by calling for the General Accounting Office to evaluate whether the more expansive testing programs in other countries might work in the United States.

"It's crucial that we implement a stringent plan to protect our food supply and our meat and dairy industries from the threat of mad cow disease," Boxer said. "Japan and the United Kingdom have both set excellent examples. We need to study the testing protocols being used in other countries and figure out which is the best plan of action to take here at home."

In Japan, all cattle are tested for mad cow disease. Great Britain's testing program also is more widespread -- and quicker -- than the current U.S. program.

Government scientists in Iowa tested 20,000 cattle for the brain-wasting disease last year; USDA Secretary Ann Veneman has vowed to nearly double that number in 2004.

That may merely be a first step to much wider testing that could include more mad cow test centers. For the first time, the USDA is considering the same kind of rapid screening for mad cow disease that is done in other countries.

Such techniques could be used by local labs across the country as a way to quickly do a first test for the disease. The tests cost about $50 per cow, which would add about 10 cents to the price of a pound of beef.

The CAHFS, which employs 180 in Davis and four satellite labs, is familiar with rapid disease tests. It already uses them for rapid screening of so-called "TSEs," such as chronic wasting disease in deer and scrapie in sheep, which are part of the same family of neurological afflictions as mad cow.

The lab is part of the U.S. mad cow surveillance system set up in 1990 as an overlapping patchwork of federal agencies. Inspectors from the federal Food Safety Inspection Service are responsible for checking for mad cow at packinghouses, farms and dairies across the country. They send samples to the USDA's Iowa lab.

Samples from ranchers or veterinarians go first to labs like the one in Davis. They notify CAHFS, which arranges to receive the head or entire cow for examination.

Once the sample is in the lab, a pathologist removes a piece of the animal's vagus nerve, which is a section of spinal cord near the base of the skull. The nerve is sterilized, cut into wafer-thin sections and placed on a microscope slide.

Then a veterinarian familiar with the disease's appearance starts the time-consuming task of peering into a microscope in search of holes in the nerve tissue associated with mad cow disease.

The process from dissection to slide preparation takes about 48 hours. If the veterinarian sees something suspicious, the cow remains are sent to Iowa, where they are prioritized for testing according to the likelihood of infection.

No California sample has ever turned up positive for mad cow, said Bradd Barr, a CAHFS pathologist, "but we've sent a few to Iowa for testing, just to be sure."

The challenge to expanding mad cow testing in the U.S. is considerable. By USDA estimates, there are approximately 250 veterinarians trained to understand the disease.

"There are few people in the U.S. who are experts on mad cow because we haven't had it here until now," said Barr, who trained at the premier mad cow lab in Britain.

And the affliction itself is difficult to diagnose in live animals because it has many of the same traits as more common maladies like rabies or cancer -- weight loss, confusion and an unsteady gait.

"Diagnosing animal disease is like hearing hoofbeats," Barr said. "You think horses first, not zebras."

Whether mad cow testing becomes more prevalent or faster depends largely on how the political and commercial winds blow in the coming weeks and months.

U.S. officials are feeling pressure from the more than 50 countries that now refuse U.S. beef, variety meats and byproducts -- a gaping $17.5 billion hole in the nation's $175 billion cattle industry. Domestic demand for beef has remained strong, however, despite the industry's initial fears that consumers would scurry to poultry, fish or pork.

That continued confidence, experts say, has blunted the effect of overseas ports' shutting out U.S. beef and slowed momentum for wider testing.

"You're not going to see much of a call for more testing until the public gets upset," said Ira Krull, a mad cow expert at Northeastern University in Boston. "But if another case pops up, all bets are off."