Electrical water bath stunning and controlled atmosphere systems are the primary methods for rendering poultry unconscious before slaughter, with significant welfare differences between methods and their application.
Stunning effectiveness is the most critical welfare factor at poultry slaughter. Inadequate stunning means birds are conscious during slaughter - an acute welfare failure. Water bath systems that cause pre-stun shocks, or that fail to stun all birds effectively due to individual size variation, cause preventable suffering. Controlled atmosphere systems using high CO2 cause aversion and distress; systems using argon or nitrogen provide insensibility without the distress period. Monitoring stunning effectiveness through animal-based indicators is essential for welfare assurance.