EEG-CBF integration in calf slaughter neurophysiology: a narrative review

Loss of consciousness (LOC) during calf slaughter is a neurophysiological process that requires distinction between cortical awareness and reflexive subcortical or spinal activity. Conscious perception depends on intact thalamocortical connectivity and integrated cortical function. Electroencephalography (EEG) and evoked potentials provide indirect measures of cortical activity, while cerebral blood flow (CBF) is the physiological prerequisite for maintaining cortical function. When cerebral perfusion fails, organized cortical electrical activity rapidly ceases. This review synthesizes current evidence on the neurophysiological effects of different slaughter methods in calves by integrating electrophysiological findings with cerebral perfusion data relevant to animal welfare assessment. A structured narrative review was conducted according to SANRA principles. PubMed/MEDLINE was systematically searched from database inception to January 2026 using predefined terms related to calves, cattle, EEG, evoked potentials, cerebral perfusion, stunning techniques, exsanguination without stunning, and religious slaughter. Only peer-reviewed studies reporting direct neurophysiological endpoints in cattle or calves were included. Correctly applied penetrating captive bolt induces rapid cortical changes consistent with loss of cortical function, with pathological evidence also demonstrating disruption of subcortical and brainstem structures. Proper electrical stunning produces an ictal phase followed by post-ictal cortical suppression characterized by EEG patterns incompatible with conscious processing. Non-penetrating captive bolt also achieves electrocortical suppression under controlled conditions, although with greater variability. In contrast, exsanguination without prior stunning causes a rapid reduction in cerebral perfusion pressure and CBF, supported by carotid hemodynamic and computational studies, although direct intracerebral measurements during slaughter are lacking. Electrophysiological studies consistently report EEG patterns compatible with LOC within single-digit seconds. Overall, current evidence indicates that catastrophic loss of cerebral perfusion after carotid transection results in rapid LOC, while available EEG findings during slaughter without stunning are consistent with this conclusion. Future validation of combined EEG-perfusion monitoring under commercial slaughter conditions may reduce uncertainty in neurophysiological welfare assessment.