Responses of Pigs to Stunning with Nitrogen Filled High-Expansion Foam
Department of Agriculture and Food, RISE Research Institutes of Sweden AB, 750-07 Uppsala, Sweden
Department of Animal Environment and Health, Swedish University of Agricultural Sciences, 532-23 Skara, Sweden
Author to whom correspondence should be addressed.
Received: 19 October 2020
Revised: 13 November 2020
Accepted: 23 November 2020
Published: 25 November 2020
Stunning pigs with carbon dioxide gas is one of the most common methods for commercial slaughter. Carbon dioxide, however, has been shown to be aversive for pigs and causes a high degree of distress before they lose consciousness. Stunning with nitrogen gas is less aversive than with carbon dioxide, and an innovative method that delivers the nitrogen gas in high-expansion foam in a closed container could potentially improve pig welfare at stunning. Pigs were exposed to either air-filled foam, nitrogen-filled foam, or no foam in air, and the behavioural and physiological responses were assessed. The pigs did not show any strong aversive behaviours when exposed to foam, regardless of whether it was air-filled or nitrogen-filled foam. However, they seemed to avoid putting their heads and snouts into the foam, and the rate of escape attempts through the lid increased when foam levels became high. Five minutes after the nitrogen foam production started, the pigs were assessed to be in deep unconsciousness or dead. Based on the results found, stunning with the nitrogen foam technique may be a viable alternative to carbon dioxide stunning and offer improved animal welfare. Further studies are needed to assess the new method for stunning of slaughter-weight pigs.