Validation of behavioural indicators used to assess unconsciousness 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.

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 ± 00:12 min and 00:59 ± 00:17 min (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.