Assessing unconsciousness in livestock at slaughter

Merel Verhoeven

Research output: Thesisinternal PhD, WUAcademic

Abstract

Assessing unconsciousness in livestock at different stages of the slaughter process is a legal requirement according to EU legislation. The assessment can be based on absence of readily observable indicators (behavioural indicators, physical signs and reflexes) or, under experimental conditions, by recording and subsequent assessment of brain activity as presented in an electroencephalogram (EEG). There is no consensus, however, to what extent different behavioural indicators, physical signs and reflexes accurately reflect unconsciousness. The aim of this thesis was to study the relationships between these readily observable indicators and EEG activity to provide information on 1. the exact point in time at which animals lose consciousness when subjected to different stunning and slaughter methods and 2. the validity of behavioural indicators, physical signs and reflexes used to assess unconsciousness at slaughter under commercial conditions. The results showed a large variation in time to loss of consciousness, based on EEG activity, both between stunning and slaughter procedures and amongst animals. Captive bolt stunned calves lost consciousness instantly following the stun. Loss of consciousness in pigs during CO2 stunning varied from 21 to 61 s after start of the exposure. An increased CO2 concentration decreased the time to loss of consciousness. Times to loss of consciousness in sheep slaughtered without stunning varied from 6 to 24 s. In cattle slaughtered without stunning, times to loss of consciousness varied from 14 s up to over two minutes. Following captive bolt stunning in calves, absence of reflexes indicated unconsciousness. When consciousness was lost gradually (e.g. CO2 stunning and non-stunned slaughter) none of the readily observable indicators could identify the exact point in time at which animals lost consciousness. Absence of rhythmic breathing, corneal reflex- and eyelid reflex were valid indicators of unconsciousness following CO2 stunning and non-stunned slaughter, but these indicators were quite conservative as they were initially absent long after EEG activity indicated unconsciousness. When presence of these indicators would require (re)stunning, many animals will have to be (re)stunned. The results also showed that under full commercial conditions, stunning effectiveness must be closely monitored by slaughter plant employees, since risks for stun failures are higher under commercial conditions compared to experimental conditions.

LanguageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
Supervisors/Advisors
  • Kemp, Bas, Promotor
  • Gerritzen, Marien, Co-promotor
  • Hellebrekers, L.J., Co-promotor, External person
Award date11 Nov 2016
Place of PublicationWageningen
Publisher
Print ISBNs9789462579064
DOIs
Publication statusPublished - 2016

Fingerprint

unconsciousness
consciousness
slaughter
livestock
reflexes
electroencephalography
animals
calves
stunning methods
bolts
eyelids
laws and regulations
human resources
breathing
brain
sheep

Keywords

  • livestock
  • slaughter
  • animal welfare
  • stunning
  • electroencephalograms
  • animal behaviour
  • consciousness
  • animal production
  • animal health
  • pigs
  • cattle
  • sheep

Cite this

Verhoeven, M. (2016). Assessing unconsciousness in livestock at slaughter. Wageningen: Wageningen University. https://doi.org/10.18174/388582
Verhoeven, Merel. / Assessing unconsciousness in livestock at slaughter. Wageningen : Wageningen University, 2016. 187 p.
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Verhoeven, M 2016, 'Assessing unconsciousness in livestock at slaughter', Doctor of Philosophy, Wageningen University, Wageningen. https://doi.org/10.18174/388582

Assessing unconsciousness in livestock at slaughter. / Verhoeven, Merel.

Wageningen : Wageningen University, 2016. 187 p.

Research output: Thesisinternal PhD, WUAcademic

TY - THES

T1 - Assessing unconsciousness in livestock at slaughter

AU - Verhoeven, Merel

N1 - WU thesis 6500 Author's name on cover: Merel Verhoeven Includes bibliographic references. - With summary in English

PY - 2016

Y1 - 2016

N2 - Assessing unconsciousness in livestock at different stages of the slaughter process is a legal requirement according to EU legislation. The assessment can be based on absence of readily observable indicators (behavioural indicators, physical signs and reflexes) or, under experimental conditions, by recording and subsequent assessment of brain activity as presented in an electroencephalogram (EEG). There is no consensus, however, to what extent different behavioural indicators, physical signs and reflexes accurately reflect unconsciousness. The aim of this thesis was to study the relationships between these readily observable indicators and EEG activity to provide information on 1. the exact point in time at which animals lose consciousness when subjected to different stunning and slaughter methods and 2. the validity of behavioural indicators, physical signs and reflexes used to assess unconsciousness at slaughter under commercial conditions. The results showed a large variation in time to loss of consciousness, based on EEG activity, both between stunning and slaughter procedures and amongst animals. Captive bolt stunned calves lost consciousness instantly following the stun. Loss of consciousness in pigs during CO2 stunning varied from 21 to 61 s after start of the exposure. An increased CO2 concentration decreased the time to loss of consciousness. Times to loss of consciousness in sheep slaughtered without stunning varied from 6 to 24 s. In cattle slaughtered without stunning, times to loss of consciousness varied from 14 s up to over two minutes. Following captive bolt stunning in calves, absence of reflexes indicated unconsciousness. When consciousness was lost gradually (e.g. CO2 stunning and non-stunned slaughter) none of the readily observable indicators could identify the exact point in time at which animals lost consciousness. Absence of rhythmic breathing, corneal reflex- and eyelid reflex were valid indicators of unconsciousness following CO2 stunning and non-stunned slaughter, but these indicators were quite conservative as they were initially absent long after EEG activity indicated unconsciousness. When presence of these indicators would require (re)stunning, many animals will have to be (re)stunned. The results also showed that under full commercial conditions, stunning effectiveness must be closely monitored by slaughter plant employees, since risks for stun failures are higher under commercial conditions compared to experimental conditions.

AB - Assessing unconsciousness in livestock at different stages of the slaughter process is a legal requirement according to EU legislation. The assessment can be based on absence of readily observable indicators (behavioural indicators, physical signs and reflexes) or, under experimental conditions, by recording and subsequent assessment of brain activity as presented in an electroencephalogram (EEG). There is no consensus, however, to what extent different behavioural indicators, physical signs and reflexes accurately reflect unconsciousness. The aim of this thesis was to study the relationships between these readily observable indicators and EEG activity to provide information on 1. the exact point in time at which animals lose consciousness when subjected to different stunning and slaughter methods and 2. the validity of behavioural indicators, physical signs and reflexes used to assess unconsciousness at slaughter under commercial conditions. The results showed a large variation in time to loss of consciousness, based on EEG activity, both between stunning and slaughter procedures and amongst animals. Captive bolt stunned calves lost consciousness instantly following the stun. Loss of consciousness in pigs during CO2 stunning varied from 21 to 61 s after start of the exposure. An increased CO2 concentration decreased the time to loss of consciousness. Times to loss of consciousness in sheep slaughtered without stunning varied from 6 to 24 s. In cattle slaughtered without stunning, times to loss of consciousness varied from 14 s up to over two minutes. Following captive bolt stunning in calves, absence of reflexes indicated unconsciousness. When consciousness was lost gradually (e.g. CO2 stunning and non-stunned slaughter) none of the readily observable indicators could identify the exact point in time at which animals lost consciousness. Absence of rhythmic breathing, corneal reflex- and eyelid reflex were valid indicators of unconsciousness following CO2 stunning and non-stunned slaughter, but these indicators were quite conservative as they were initially absent long after EEG activity indicated unconsciousness. When presence of these indicators would require (re)stunning, many animals will have to be (re)stunned. The results also showed that under full commercial conditions, stunning effectiveness must be closely monitored by slaughter plant employees, since risks for stun failures are higher under commercial conditions compared to experimental conditions.

KW - livestock

KW - slaughter

KW - animal welfare

KW - stunning

KW - electroencephalograms

KW - animal behaviour

KW - consciousness

KW - animal production

KW - animal health

KW - pigs

KW - cattle

KW - sheep

KW - vee

KW - slacht

KW - dierenwelzijn

KW - bedwelmen

KW - elektro-encefalogrammen

KW - diergedrag

KW - bewustzijn (consciousness)

KW - dierlijke productie

KW - diergezondheid

KW - varkens

KW - rundvee

KW - schapen

U2 - 10.18174/388582

DO - 10.18174/388582

M3 - internal PhD, WU

SN - 9789462579064

PB - Wageningen University

CY - Wageningen

ER -

Verhoeven M. Assessing unconsciousness in livestock at slaughter. Wageningen: Wageningen University, 2016. 187 p. https://doi.org/10.18174/388582