The ruling follows a preliminary injunction issued last month by Baltimore's U.S. District Court that included an order for the company to immediately cease advertising its chicken as raised without antibiotics that impact antibiotic resistance in humans. Tyson had then requested the federal appeals court in Richmond, Va., to stay the ruling by the Baltimore judge.

"We're disappointed the motion for a stay has been denied and are evaluating our legal options," said Tyson Foods spokesman Gary Mickelson. The firm said it has already contacted stores about removing POP (point-of-purchase) advertising.

The action was sparked off by rival poultry processing companies Perdue Farms and Sanderson Farms. The two companies had filed the suit against Tyson in a joint injunction that sought to stop Tyson's ad campaign. The competitors argued that Tyson's marketing campaign for the "raised without antibiotics thought to lead to drug resistance in humans" claim misleads consumers because none of the companies use those types of drugs. Sanderson said it lost $4 million in sales since last year as a result of the Tyson campaign, while Perdue contended it lost $10 million.

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Tyson started marketing its retail fresh chicken under a USDA accepted "Raised Without Antibiotics" label in summer 2007. After the USDA claimed an error in its approval of a fully-disclosed antimicrobial feed ingredient under the claim, the company later sought and received approval for a modified label, which reads "Raised Without Antibiotics that impact antibiotic resistance in humans."

Tyson said in a statement that the preliminary injunction does not affect the USDA-approved product label used on Tyson's retail fresh chicken products. It does affect Tyson’s advertising of the products, the firm added.