Chickens bred for Nando’s restaurants were swung by the neck and found paralysed by deformities during an undercover investigation.
Others were filmed still apparently displaying signs of life but being dumped in a wheelbarrow alongside carcasses of dead birds.
The secret footage, taken at three farms in England that supply the fast-food giant, also shows baby chicks thrown into buckets after being killed because they were said to be sick or growing too slowly.
The chickens had skeletal and joint disorders, activists claim, and some were unable to stand or move because the breed was engineered to grow abnormally quickly, leaving their limbs and hearts unable to cope.
Animal-welfare charity World Animal Protection uncovered the “harrowing” conditions when it filmed in huge barns housing thousands of chickens.
The restaurant chain says it is investigating with the suppliers.
The witnesses said they saw chickens with legs splayed out, a sign of skeletal and joint disorders caused by exceptionally rapid weight gain, and others with severely damaged backbones, pinching the spinal cord which causes paralysis.
Chickens were also filmed being thrown into buckets or a wheelbarrow after being killed, and some, still moving, appeared to be in distress or in the throes of dying.
At one point in the footage, a worker kills birds by swinging them by their necks.
Cramped conditions in some areas prevented birds from behaving naturally, the group claimed.
The Red Tractor scheme says its endorsement means food has been produced to “high quality standards with great care and attention”.
Standards also require that euthanasia complies with Humane Slaughter Association guidance.
Ian Woodhurst, of World Animal Protection, said: “This distressing footage showcases the harrowing conditions that fast-growing chickens endure on farms that supply Nando’s.
“We feel it’s important for customers to see the truth about the chickens it uses.”
He said Nando’s chiefs had refused to discuss the footage.
The charity wants customers to lobby the company to stop using fast-growing breeds. “If not, Nando’s chickens will continue to suffer catastrophic health issues and live their short lives in unnecessary pain,” Mr Woodhurst said.
Research by the group shows that 38 per cent of Nando’s customers believe the chain has the highest chicken welfare policies of the big fast food brands. But a report last year by the group ranked it among the worst.
A Nando’s spokesperson said: “We take animal welfare very seriously, knowing it’s as important to our customers as it is to us.
“We are extremely shocked by this footage and have started a full investigation with the supplier to find out what happened and to ensure it doesn’t happen again.”
The Independent has also asked Nando’s to comment on claims it refused to discuss the footage.
A Red Tractor spokesperson said: “Protecting animal health and welfare is one of our top priorities, and we take any allegations of breaches to our standards very seriously.
“As soon as we were made aware of the footage, we launched an immediate investigation to identify the farms and review the behaviours seen. Corrective action will be taken where necessary.”
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