Talk about closing the door after the sick cow has left the barn. This episode shows the need for stricter enforcement of food-safety regulations, and more government inspectors.

The USDA on Sunday announced the recall of 143 million pounds of ground beef from a California slaughterhouse that supplies burgers, meatballs and taco meat to school lunch programs. The action calls into question the safety of beef dating back to February 2006.

Most of that meat has already been eaten, including by children in at least 150 school districts around the nation. The slaughterhouse, Westland/Hallmark Meat Co. of Chino, Calif., delivered 37 million pounds of ground beef for the National School Lunch Program and other government nutrition programs. Some of the meat was sold to fast-food chains.

Officials at the USDA don't think the meat was tainted, but they really don't know for certain. That's because government inspectors didn't catch this problem. The violations were exposed in a video by the Humane Society of the U.S., which secretly filmed a horror show at Hallmark.

The video shows two slaughterhouse employees using forklifts and electric prods to move cows that are too sick or too weak to walk. Cows that can't walk, also called "downer cows," are banned from use in food because they pose a much greater risk of mad-cow disease. Because they often wallow in feces, these cows also raise the risk of E. coli contamination.

USDA says it has about 7,800 inspectors to examine 6,200 slaughterhouses and food processors nationwide. But after an E. coli outbreak in 2007 that was traced to a meatpacking plant in Elizabeth, N.J., some federal inspectors complained about 1,000 vacancies in their ranks. They said the USDA wasn't replacing retiring inspectors, and those employees who remain must inspect as many as five plants per day.

The risk of mad-cow disease spreading in the food supply is very low. The animals' brains and spinal cords, where the disease is most often found, would not have been used in food for humans.

Even so, the violations that occurred under the noses of USDA inspectors raise serious concerns about whether the government is up to the job of protecting the public health. It's time to, ah, beef up the number of inspectors and the scrutiny at slaughterhouses.