Evaluation of inert gases as alternatives to Carbon Dioxide for stunning pigs: effects on gas stability, effectiveness and animal welfare

Abstract

The European Union requires pigs to be stunned before slaughter, with Carbon Dioxide (CO₂) being the most common method, although it is increasingly criticized for its aversiveness. This study evaluated inert gases for stability, effectiveness, and animal welfare. Ten gas mixtures were pre-tested in a plexiglass box, with 100% Argon (Ar), 85% Argon/15% CO₂ (ArCO₂), and 50% Argon/50% Nitrogen (ArN₂) selected for animal trials. A total of 160 piglets (30–50 kg) were stunned and slaughtered, with CO₂ serving as standard method. All gases remained stable under experimental conditions, and weather had no influence. Carbon Dioxide elicited strong aversive reactions. Mild responses occurred with ArCO₂. Loss of posture occurred the fastest in CO₂, and the slowest in Ar. In conclusion, inert gases and their mixtures provided effective stunning with markedly reduced aversive behaviour compared to CO₂, although requiring longer exposure times. Further validation is recommended under commercial slaughter conditions.