The Food and Drug Administration on Monday took some of its biggest steps yet to protect the American public against mad cow disease.

Cattle can get the brain-wasting disease only by eating food that contains protein from infected bovines. The nation's first case of mad cow was discovered Dec. 23 in Washington state.

The FDA announced the immediate elimination of several exemptions to existing regulations prohibiting the feeding of ruminant remains (cows, sheep and goats) to other ruminants.

Blood may no longer be fed to ruminants, and poultry litter and restaurant plate waste may not be used as feed ingredients. These are inexpensive sources of protein and roughage.

Mad cow disease is present in nervous system tissue but has been found in other tissue as well. People can get a sometimes fatal version of the disease by eating infected tissue.

Feed plants using protein for other animals that is banned in ruminant feed must now use separate production lines to prevent contamination.

''We know that no one set of measures is something that we should depend on for an illness that's as potentially serious as BSE (bovine spongiform encephalopathy -- the scientific name for mad cow),'' FDA Commissioner Mark McClellan said. ''So we've implemented a multiple firewall approach based on the best science.''

Expanded oversight will include annual inspections of all renderers and feed mills that process products with materials prohibited in ruminant feed.

Under the often-arcane laws governing the food supply, the FDA is responsible for foods with less than 3 percent cooked meat, while the Department of Agriculture is responsible for those with more than 3 percent. FDA also regulates cosmetics and dietary supplements, which under the law are considered food. Cosmetics can contain collagen, oils and gelatins made from bovines.

The new rules will ban certain bovine materials from FDA-regulated human food, supplements and cosmetics. They include:

* Material from ''downers,'' cattle that cannot walk. The infected dairy cow was a downer.

* Material from cattle that died before they reached slaughter.


Brains, skulls, eyes and spinal cords of cattle 30 months and older.


The small intestine and tonsils.

Consumer groups have long agitated for strengthened regulations. One important loophole is left, says Michael Hansen of Consumers Union. ''It's perfectly legal under these new rules to feed rendered cattle material to pigs and chickens and then feed chicken and pig materials back to cattle.''