Behavioural responses during exposure of broiler chickens to different gasmixtures

An alternative stunning system to the generally applied electrical water ba th stunner for broiler chickens is gas stunning. This method of stunning ca n eliminate the stress associated with uncrating and/or shackling of live b irds prior to electrical stunning. Behavioural responses to inhalation of g as were examined during exposure of broilers to different gas mixtures. In total, 137 six-week-old broiler chickens were individually immersed in a ga s chamber containing one of the following gas mixtures: (a) 90% Ar/air, (b) 30% CO2/60% Ar/air or (c) 40% CO2/30% O-2/30% N-2. The birds moved freely or were restrained. Behavioural parameters were recorded on video and analy sed for gasping, headshaking, wing flapping and loss of posture. The number of gasps before loss of posture declined progressively on exposure to gas mixtures Ar/air or Ar/CO2/air or CO2/O-2/N-2, respectively, and remained hi gh after loss of posture in the latter gas mixture. Gasping occurred rarely in broilers during exposure to gas mixture Ar/air. When gas mixture CO2/O- 2/N-2 was used the loss of posture was significantly delayed compared to th e gas mixture Ar/air and Ar/CO2/air. The number of headshakes and wing flap ping was significantly higher in the restrained groups of birds compared to the free moving group. Wing flapping was low before and after loss of post ure in gas mixture CO2/O-2/N-2 It is concluded that during the immersion in gas mixtures broilers show gasps, head shakes and wing flapping which star t before loss of posture, which may cause some distress. However, it can be argued that gas stunning compared to water bath stunning is preferred in p ractical applications, because the live broilers do not need to be uncrated and/or shackled. (C) 1999 Elsevier Science B.V. All rights reserved.