Washington ? To bolster confidence in U.S. beef, Agriculture Secretary Ann Veneman on Tuesday banned sick and injured cattle — those at the highest risk to have mad cow disease — from the nation’s food supply.

In a series of actions that even critics lauded, Veneman also moved to:

l Prohibit human consumption of certain high-risk cow parts from older cattle, including the brain, eyes, spinal cord and small intestines

l Tighten restrictions on controversial slaughterhouse techniques that heighten contamination risks

l Require inspectors to hold potentially ill animals out of the food supply until tests confirm they are safe

l Speed up plans for a comprehensive national system to track cattle

The moves follow the Dec. 23 discovery of the first U.S. case of mad cow disease at a slaughterhouse in Washington state. Many countries are rejecting U.S. beef, and futures markets for February beef deliveries have plummeted about 15 percent since then.

“While we are confident that the United States has safeguards and firewalls needed to protect public health, these additional actions will further strengthen our protection systems,” Veneman said at a Tuesday afternoon news conference.

Afterward, beef industry officials lauded the changes, which they had long resisted. The new rules are unlikely to add to the price that consumers pay for beef, Veneman said.

The biggest change is the ban on “downer animals,” which can’t walk because of illness or injury. They number about 195,000 out of the 35.7 million U.S. cattle slaughtered each year. The U.S. mad cow case, in Mabton, Wash., involved a downer cow.

Until Tuesday, more than 90 percent of the downer cattle went into the meat supply without being tested for mad cow disease, formally known as bovine spongiform encephalopathy. In the budget year that ended Sept. 30, Veneman’s department tested only 16,560 downer cattle. That’s about 8.5 percent of all downers.

Peter Jinman, a veterinarian who serves on the United Kingdom’s special mad-cow scientific advisory panel, told Knight Ridder Newspapers that he was surprised the United States had been testing such a “very small percentage” of potentially hazardous cattle.

Japan and Europe already have standards comparable to the new restrictions. The Agriculture Department already banned meat from downed animals from being included in school lunches. So have major fast food chains such as McDonald’s, Wendy’s and Burger King.

A USDA study published in August reported that downer cows are 3.3 times more likely than healthy cows to have the often-fatal type of E. Coli infection that sickens 73,000 people and kills 60 a year. Downer cattle also are more likely to carry salmonella, which sickens 1.3 million people annually and kills 550 people a year, according to American University scholar-in-residence Susan Solarz, a former USDA biologist.