Welfare assessment of Low Atmospheric Pressure Stunning (LAPS) in boiler chickens

In 2015 over 59 billion broiler chickens were produced globally for human consumption and therefore the method of how these birds are stunned and slaughtered is paramount to maintaining welfare on a large scale. A novel pre-slaughter stunning method for chickens has been developed, where birds are rendered unconscious by progressive hypobaric hypoxia, this approach shares many of the welfare advantages of controlled atmosphere stunning (CAS) systems, which irreversibly stun poultry by exposure to hypoxic and/or hypercapnic gas mixtures (in a 280s cycle). We examined responses to LAPS at two temperature settings by recording behaviour, electroencephalogram (EEG) and electrocardiogram (ECG) in broilers and interpreted these with regards to welfare impact. All birds showed no signs of life at the end of LAPS. Birds showed a consistent sequence of behaviours during LAPS (ataxia, loss of posture, clonic convulsions and motionless) which were observed in all birds. Spectral analysis of EEG responses at 2 s intervals throughout LAPS revealed progressive decreases in median frequency at the same time as corresponding progressive increases in total power, followed later by decreases in total power as all birds exhibited isoelectric EEG and died.in general responses to LAPS were consistent and similar to those reported in previous research on controlled atmosphere stunning. The results suggest that the process is humane (slaughter without avoidable fear, anxiety, pain, suffering and distress). In particular, the maintenance of slow wave EEG patterns in the early part of LAPS (while birds are still conscious) is strongly suggestive that LAPS is non-aversive, since we would expect this to be interrupted by pain or discomfort. This evidence is part of that presented to the European Commission to facilitate the approval of LAPS in the EU.

By Dr Jessica Martin (University of Edinburgh) and Dr Dorothy McKeegan (University of Glasgow), both AWRN members.

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