Ron Hayes, who owns six cats and two dogs, said he hasn't changed their diet since learning about the country's first confirmed case of mad cow disease (search).

"It's called mad cow disease, not mad dog disease, right?" he asked, but then checked to see if his pet foods contained beef ingredients. He spotted beef tallow (searchon a bag of dry food.

"I'll have to think about it now," he said.

Federal regulators and experts say there's still no reason to worry about pets getting sick from pet food and no evidence to suggest any tainted meat has made its way into the pet food supply.

Experts say the chances of cats in the United States contracting the disease are slim, though not impossible. There's never been a reported case of a dog getting it.

"There is no evidence that dogs have ever gotten this disease," said Alfonso Torres, associate dean at Cornell University's College of Veterinary Medicine. "There's no evidence that cats will contract the disease under normal circumstances."

Since 1997, the United States has banned the practice of feeding cattle, sheep and goats any food that contains brain and spinal cord material. Eating contaminated feed is the only known way the disease spreads among livestock.

The Food and Drug Administration (search), which regulates animal feed and pet food, says it plans to extend that ban to food for dogs, cats, pigs and poultry in 2007.

Mad cow has been found in a small number of cats — about 100 — in the United Kingdom, as well as a handful in other European countries. Larger zoo felines that fed directly off infected carcasses also died from the disease, Torres said.

Officials in the United Kingdom and elsewhere have said they suspect the cats got the disease by eating cat food tainted with infected meat. That suspicion is bolstered by evidence that British cats contracted the disease at about the same time, and in the same places.

"Your gut tells you yes, and the reports tell you yes, because they're linked temporally and geographically," said Dr. Niels Pedersen, a specialist in feline infectious diseases at the University of California at Davis.

In the United States, pet food is closely inspected for quality and safety, Pedersen said, in part because some of it ends up eaten by humans.

"It would be highly, highly unlikely that nervous tissue would end up even in pet food," he said. "It's one of those products that is as vigorously inspected and quality-controlled as canned tuna."

In a statement released Tuesday, Stephen Sundlof, director of the Center for Veterinary Medicine at the Food and Drug Administration, said some animals declared unfit for people can be used in pet food.

"But they must be processed in such a way that they are deemed safe for the pets. This generally means that the pet food must be heat-treated or the animal-derived parts must be rendered to destroy any pathogens," he said.

The nation's $12 billion pet food industry feeds 76 million cats and 61 million dogs, according to the Pet Food Institute, a trade group.