Pre-slaughter stunning of pigs is required in the EU and UK to prevent unnecessary suffering, with different stunning methods having distinct welfare profiles and limitations.
Pre-slaughter stunning welfare depends critically on the method used and its proper application. Electrical stunning, when properly applied, induces immediate unconsciousness but is dependent on correct electrode placement and current parameters that are not always achieved in practice. High-concentration CO2 stunning causes a period of dyspnea and distress before unconsciousness is reached, which is the primary welfare criticism of this widely used method. Research shows pigs show avoidance behavior entering CO2 gas chambers, indicating aversion to the stimulus. Stunning failures, where animals are not properly rendered unconscious before sticking, allow animals to regain consciousness during the slaughter process, causing severe welfare harm.