The slaughter of poultry involves billions of birds annually in conditions where welfare problems at small scales become enormous problems when multiplied across industrial volumes.
The scale of poultry slaughter makes even small rates of welfare failure enormous in absolute terms. At 9 billion birds per year in the US, a 1% stunning failure rate means 90 million conscious birds reaching slaughter each year. Water bath stunning systems have significant welfare problems including pre-stun shocks from water contact and birds that avoid the stunner by raising their heads. Controlled atmosphere killing eliminates these problems but requires investment in new infrastructure. Consumer demand for higher welfare products can incentivize industry adoption of better systems.