WASHINGTON -- Agriculture Secretary Ed Schafer announced Tuesday a total ban on the slaughter at meat plants of cows too sick or weak to stand.

The planned change comes in the wake of the nation's largest beef recall. It would shut down an exception -- which critics call a loophole -- that allows a small number of so-called "downer" cattle into the food supply if they pass veterinary inspection.

Downer cows pose increased risk for mad cow disease, E. coli and other infections, partly because they typically wallow in feces. They are already mostly banned from slaughter, but under current rules can be allowed in if they fall down after passing an initial veterinary inspection, and then are reinspected and pass that second inspection, too.

Some lawmakers and the Humane Society of the United States have lobbied Schafer to eliminate that exception, and the meat and dairy industry last month reversed its opposition and endorsed the change, too.

Texas is the nation's largest cattle-producing state.

Schafer announced the planned new rule to reporters following a 60-day review of conditions at the nation's slaughterhouses. The department hopes to finalize the rule within several months.

The review was prompted by a 143 million-pound beef recall in February, ordered after the Humane Society released undercover video showing employees abusing downer cows at Westland/Hallmark Meat Co. in Chino, Calif. Downer cows at the plant were forced to slaughter without the required second veterinary inspection, which is why the recall was ordered.