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Physiological and behavioural responses of broilers to controlled atmosphere stunning: implications for welfare

Published online by Cambridge University Press:  11 January 2023

DEF McKeegan ,
JA McIntyre ,
TGM Demmers ,
JC Lowe ,
CM Wathes ,
PLC van den Broek ,
AML Coenen  and
MJ Gentle
DEF McKeegan*
Affiliation:
Division of Animal Production and Public Health, Faculty of Veterinary Medicine, University of Glasgow, Bearsden Road, Glasgow, G61 1QH, Scotland, UK Roslin Institute, Roslin, Midlothian, EH25 9PS, Scotland, UK
JA McIntyre
Affiliation:
Roslin Institute, Roslin, Midlothian, EH25 9PS, Scotland, UK
TGM Demmers
Affiliation:
Silsoe Research Institute, Wrest Park, Silsoe, Bedford, MK45 4HS, UK
JC Lowe
Affiliation:
Silsoe Research Institute, Wrest Park, Silsoe, Bedford, MK45 4HS, UK
CM Wathes
Affiliation:
Silsoe Research Institute, Wrest Park, Silsoe, Bedford, MK45 4HS, UK
PLC van den Broek
Affiliation:
Radboud University Nijmegen, NICI, Department of Psychology, POB 9104, NL-6500 HE Nijmegen, The Netherlands
AML Coenen
Affiliation:
Radboud University Nijmegen, NICI, Department of Psychology, POB 9104, NL-6500 HE Nijmegen, The Netherlands
MJ Gentle
Affiliation:
Roslin Institute, Roslin, Midlothian, EH25 9PS, Scotland, UK
*
* Contact for correspondence and requests for reprints: d.mckeegan@vet.gla.ac.uk
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Abstract

Controlled atmosphere (gas) stunning (CAS) has the potential to improve the welfare of poultry at slaughter but there is a lack of consensus about which gas mixtures are most humane. The aim of this study was to evaluate the welfare consequences of different gas stunning approaches. Individual broilers were exposed to gas mixtures capable of inducing unconsciousness and euthanasia while their behavioural, cardiac, respiratory and neurophysiological responses were measured simultaneously. The approaches investigated included anoxia (N2 or Ar with < 2% residual O2), hypercapnic anoxia (30% CO2 in Ar, 40% CO2 in N2) and a biphasic method (40% CO2, 30% O2, 30% N2 for 60 s followed by 80% CO2 in air). Evaluation of the welfare implications of each approach centred on the likelihood of them inducing negative states or experiences during the conscious phase. Hypercapnic mixtures were associated with strong respiratory responses, while anoxic mixtures induced vigorous wing flapping. Electroencephalogram analysis using the correlation dimension (a non-linear measure of complexity) suggested that anoxic wing flapping occurred during periods in which a form of consciousness could not be excluded. Hypercapnic hyperoxygenation (biphasic approach) exacerbated respiratory responses but eliminated the possibility of vigorous behavioural responses occurring during a conscious phase. The relative importance of respiratory discomfort versus the potential to induce significant distress due to convulsive wing flapping and associated trauma is a matter for debate. We argue that respiratory discomfort is unpleasant but may be preferable to the risk of vigorous wing flapping and associated injury while conscious in poultry during CAS.

Keywords

animal welfarebroilerscarbon dioxideeuthanasiagas stunningslaughter
Type
Articles
Information
Animal Welfare , Volume 16 , Issue 4 , November 2007 , pp. 409 - 426
Copyright
© 2007 Universities Federation for Animal Welfare

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