Stunning pigs with different gas mixtures: gas stability

Abstract

AbstractThe stability and uniformity of the following gas mixtures: 90% argon; 85% argon and 15% carbon dioxide (CO2); 70% argon and 30% CO2; 98% nitrogen (N2); 92% N2and 8% CO2; 90% N2and 10% CO2; 85% N2and 15% CO2; 80% N2and 20% CO2; 70% N2and 30% CO2; and 90% CO2by volume in atmospheric air were assessed in a commercial dip-lift stunning system when the cradle was either stationary or in motion. The gas mixtures of 90% argon, 85% argon and 15% CO2, 70% argon and 30% CO2, 85% N2and 15% CO2, 80% N2and 20% CO2, 70% N2and 30% CO2and 90% CO2by volume in atmospheric air could be sustained in a commercial dip-lift stunning system. The stability of the gas mixtures 92% N2and 8% CO2, and 90% N2and 10% CO2by volume in atmospheric air were lower than in the previous cases. On the other hand, an N2concentration higher than 94% by volume in atmospheric air could not be sustained in the stunning system. In addition, gas mixtures of argon and CO2showed a higher stability than gas mixtures of N2and CO2. The uniformity at different levels inside the pit (defined as the capacity of the gas to maintain its concentration constant at different levels inside the pit) was higher in 90% argon, or argon and CO2mixtures and N2and CO2mixtures than in 90% CO2. This fact ensures that for the whole time the animals are inside the pit, the same conditions are applied, which is not the case for 90% CO2.