Behavioural response in pigs at gas stunning in foam

Abstract: There are several stunning methods used for the commercial slaughter of pigs. The two most common are electric stunning and stunning with carbon dioxide gas. It has been shown that there are several problems related to animal welfare in the stunning methods used today in commercial slaughter. This master thesis was conducted as a part of a broader study aiming to evaluate the use of a new method for gas stunning with high-expansion foam. This study aimed to investigate the differences in pigs’ immediate reaction to high-expansion foam when stunned with nitrogen, argon or carbon dioxide. The study included a total of 36 pigs, divided into three groups (n=12 per group). The three groups were exposed to three different gas stunning treatments; nitrogen, argon, or carbon dioxide in foam. An ethogram consisting of 12 behaviours was conducted for video-based recording of behaviours. The observations started at the initiation of the foam in the stunning box and continued until the foam filled the entire stunning box. The result show that the pigs expressed higher frequencies of exploration behaviours when exposed to nitrogen- and argon high-expansion foam, while they expressed higher frequencies of escape attempts when exposed to carbon dioxide high-expansion foam. These findings suggest potential advantages of using nitrogen or argon for stunning pigs with high-expansion foam from an animal welfare point of view. Understanding the behavioural response can contribute to refining stunning techniques, emphasizing the importance of considering the wellbeing of animals during stunning in development and implementation of slaughter practices.