Validation of behavioural indicators used to assess unconsciousness in sheep

• Published in: Research in veterinary science 2015-08, Vol.101, p.144-153
• Main Authors: Verhoeven, M.T.W., Gerritzen, M.A., Kluivers-Poodt, M., Hellebrekers, L.J., Kemp, B.
• Format: Article
• Language: English
• Subjects: (Un)consciousness; Abattoirs - standards; Anesthesia; Anesthesia - veterinary; Animals; bispectral index; broiler-chickens; Carotid arteries; Conflicts of interest; Consciousness; Consciousness - physiology; EEG; electroencephalographic responses; Electroencephalography; Electroencephalography - veterinary; Experiments; Eyelids - physiology; halothane-anesthetized calves; Non-stunned slaughter; pigs; Propofol; Propofol - administration & dosage; Propofol - pharmacology; Reflex - physiology; Reflexes; Respiration; Sheep; Sheep - physiology; slaughter; spectral edge frequency; Unconsciousness - diagnosis; Unconsciousness - veterinary; Variables; ventral-neck incision; Veterinary medicine
• ISSN: 0034-5288; 1532-2661
• DOI: 10.1016/j.rvsc.2015.06.007

The validity of behavioural indicators to assess unconsciousness under different slaughter conditions is under (inter)national debate. The aim of this study was to validate eyelid-, withdrawal-, threat reflex and rhythmic breathing as indicators to assess unconsciousness in sheep. Sheep were monitored during repeated propofol anaesthesia (n=12) and during non-stunned slaughter (n=22). Changes in the EEG and behavioural indices of consciousness/unconsciousness were assessed and compared in sheep. Threat reflex and rhythmic breathing correlated with EEG activity during propofol anaesthesia whilst absence of non-rhythmic breathing or threat reflex indicated unconsciousness. None of the behavioural indicators correlated with EEG activity during non-stunned slaughter. Absence of regular breathing and eyelid reflex was observed 00:27±00:12min and 00:59±00:17min (mean±SD) respectively after animals were considered unconscious, indicating that absence of regular breathing and eyelid reflex are distinctly conservative indicators of unconsciousness during non-stunned slaughter in sheep. •The study compared EEG and behavioural indicators of consciousness/unconsciousness.•Behavioural indicators correlated well with EEG activity during propofol anaesthesia.•Behavioural indicators did not correlate well with EEG activity after non-stunned slaughter.