WASHINGTON — The Department of Agriculture said Tuesday that it wants to ban all "downer" cattle from the food supply, a step that consumer advocates say would promote food safety but that federal officials say is chiefly an attempt to allay consumer fears.

The proposal, which could take effect within a few months, follows the largest beef recall in U.S. history earlier this year after secretly recorded videotape showed California meat plant workers using forklifts and electric prods on immobile animals to get them to the slaughterhouse.

"There should be no longer even a slim possibility of transporting a cow to market that is too weak to rise or to walk on its own," Agriculture Secretary Ed Schafer told reporters.

"This action sends a clear message to consumers in both domestic and in international markets that we will continue to uphold the highest standards to protect our food supply and deliver the highest quality products."

Schafer also said that "by reducing the incentive to send weak and marginal cattle to slaughter, it will reduce the likelihood that those animals will be subjected to inhumane handling at processing plants."

Government regulations already prohibit slaughtering cattle for food if the animals cannot stand or walk on their own.

Cows that cannot stand are supposed to be kept out of the food supply in part because they may be infected with bovine spongiform encephalopathy, or mad cow disease.

But an exception in the regulations allows a government veterinarian to approve for slaughter an animal that passed initial inspection but went down before reaching the "knock box"—if a second inspection determines the animal isn't sick but is suffering from an acute injury such as a broken leg.

The USDA now wants to eliminate that exception so that any cow unable to stand would be condemned.

Concerns about the safety of the food supply have dogged the department and the meat industry since the release in January of secretly recorded video footage of inhumane treatment of cattle at the Westland/Hallmark Meat Packing Co. plant in Chino, Calif.