Stunning before slaughter is required by law in the UK for all farm animals, with exemptions for religious slaughter. The welfare science of effective stunning is well developed but inconsistently applied.
Stunning before slaughter, when applied correctly, renders animals insensible before they experience pain from the slaughter process. When applied incorrectly — insufficient voltage, poor electrode placement, missed bolts — animals may regain or fail to achieve consciousness and experience severe pain. The welfare science strongly supports mandatory effective stunning for all animals, and the exemption for religious slaughter creates a significant welfare problem given the volumes involved. The debate requires honest engagement with both welfare evidence and religious freedom considerations, but the welfare case for effective stunning before all commercial slaughter is clear.