Electrical versus CO2 stunning of pigs: effects on animal welfare and meat quality

Abstract

Electrical stunning and submersion in high concentrations of CO2 are the two main methods of pre-slaughter stunning of pigs. While electrical stunning results in instantaneous unconsciousness, CO2 is considered very aversive and exposure times often exceed 30s until unconsciousness, raising questions about animal welfare. However, most CO2 stunning systems involve handling of pigs in groups, resulting in lower pre-slaughter stress compared to moving pigs in single file through a raceway, as is common with electrical stunning. CO2 stunning generally results in better meat quality than electrical stunning, although there is variation both within and between systems. The improved meat quality with CO2 stunning may partly be the result of the physiological process post-mortem caused by the stunning system per-se. However, meat quality is more likely to be affected by both the stunning method as well as pre-stunning stress, which is generally lower with CO2 systems. Acceptable meat quality can be achieved by both stunning methods and the focus should be on minimizing pre-slaughter stress to improve meat quality, regardless of stunning method.