Within the next year, Tyson, the biggest US chicken company, will launch a pilot programme at two processing plants to use gas instead of electricity to stun birds before they are killed.
The plan "is a significant step forward for us in understanding if this is scalable," Justin Whitmore, Tyson's chief sustainability officer, said.
The project is part of a broader shift in production practices in the US poultry industry. Such changes generally increase costs.
In January, US chicken processor Pilgrim's Pride touted GNP's use of gas-stunning when it paid $350-million (about R4.5-billion) to buy the rival.
In GNP's system, birds are lowered into a sealed tunnel in specially designed modules where the amount of carbon dioxide gradually rises to 70% from 5%.
In minutes, the chickens pass out as carbon dioxide displaces the oxygen in the air.
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