Pig slaughter welfare depends critically on effective stunning before bleeding, and the choice of stunning method has major implications for the welfare of millions of pigs slaughtered annually.
Pig slaughter welfare is one of the most researched areas in applied animal welfare science. The standard high-CO2 controlled atmosphere stunning used in most UK pig abattoirs is effective but causes 15-30 seconds of aversion including breathlessness and panic responses before unconsciousness. The animal welfare community broadly considers this problematic. Low-oxygen and argon-based atmospheres induce unconsciousness more smoothly but are more expensive and less widely adopted. Electrical stunning can achieve equivalent humaneness when properly applied but equipment maintenance and operator training are critical. Free-farrowing and higher welfare production systems sometimes cannot justify the abattoir investment needed for optimal slaughter welfare.