A US supplier for Kentucky Fried Chicken has fired 11 workers after a video showed the poultry being kicked, stamped on and slammed against walls.
Pilgrim's Pride and KFC say they are appalled by the abuse
Pilgrim's Pride vowed to root out all who were responsible for the abuse at its Moorfield plant in West Virginia.
It came after the animal welfare group Peta released a secretly taped video showing workers "stomping on, kicking and throwing live chickens about".
KFC said it had suspended the buying of chicken from Moorfield.
Pilgrim's Pride - the country's second-largest poultry producer - said it had fired three managers and eight hourly workers as a result of its own internal investigation.
"While we are making considerable progress with our investigation, we will continue with this investigation until we're confident that every employee - regardless of rank - who had knowledge of these incidents has been held accountable for their actions," said company president, OB Goolsby.
The firm said in a statement it had also called in a leading animal welfare expert to review its practices at the plant.
"Pilgrim's Pride places a high priority on humane treatment of poultry not only because it's the right thing to do, but because it also helps assure high-quality, healthful products for consumers," it said.
An investigator for Peta, People for the Ethical Treatment of Animals, secretly recorded workers at the plant between October and May.
The group said footage showed staff stamping on the chickens, kicking them and throwing them about the slaughterhouse.
Its investigator also saw workers "ripping birds' beaks off, spray painting their faces, twisting their heads off, spitting tobacco into their mouths and eyes, tying their legs together for 'laughs'," Peta added.
The group is calling on state prosecutors to charge the workers and managers with animal cruelty.
Peta said it selected the plant because it is a major supplier to KFC, a long-time target of the group.
KFC said in a statement it was "appalled" by the actions of the workers.
The fast food chain said it would not be buying from the plant until Pilgrim's Pride "can assure us there are no instances of animal abuse there".
The firm said it had also installed an inspector at the facility to ensure its guidelines were being followed.