Egged on by competitors, a federal appeals court has given Tyson Foods 14 days to remove advertising that claims its chickens are safer to eat because they are "raised without antibiotics."

The appeals court in Richmond, Va., denied Tyson's appeal of a Baltimore judge's ruling last April and ordered the company to start removing its ads from stores and the media.

Tyson's competitors, Sanderson and Perdue, had filed suit claiming that Tyson's ads were misleading because none of the companies use the types of antiobiotics that can lead to drug resistance in humans. Sanderson said it lost $4 million in sales since last year as a result of the Tyson campaign, while Perdue contended it lost $11 million.

"We're disappointed the motion for a stay has been denied and are evaluating our legal options," Gary Mickelson, a spokesman for Tyson Foods, Springdale, Ark., said in a statement. "We continue to believe we have acted responsibly in the way we have labeled and marketed our products and intend to stand our ground." The company said it has already contacted stores about removing POP advertising.

Tyson, the world's largest meat processor, spent an estimated $70 million on the "raised without antibiotics" campaign.

USDA admits error

The U.S. Department of Agriculture (USDA) said it made a mistake in May 2007 when it approved the Tyson labeling. The decision is a big blow to Tyson, which has staked its brand's reputation on the no-antibiotics claim.

The controversy revolves around medications added to poultry feed to keep chickens from getting intestinal infections that can cause weight loss and death in poultry.

The medication -- ionophores -- is not technically an antibiotic, Tyson said, insisting it's really an antimicrobial.

But in a letter to Tyson, USDA said its longstanding policy is that "ionophores are antibiotics," The Wall Street Journal reported.

Tyson claims the USDA has known all along that it was using ionophores but senior government officials said they only learned of it recently.