Neurological mechanisms relevant for slaughter

This review (which will be followed by a second article) describes the neurobiological mechanisms that are relevant for the stunning and killing process of animals in the abattoir. The mechanisms underlying the loss of consciousness depend on the technique used: mechanical, electrical or gas stunning. Direct exsanguination (without prior stun) causes also a loss of consciousness before inducing death. The underlying mechanisms may involve cerebral anoxia or ischemia, or the depolarisation, acidification and/or the destruction of brain neurons. These effects may be caused by shock waves, electrical fields, the reduction or arrest of the cerebral blood circulation, increased levels of CO2 or a lack of O2 in the air, or the mechanical destruction of neurons. The targeted brain structures are the reticular formation, the ascending reticular activating system or the cerebral hemispheres in a general manner. Some of the techniques, when properly used, induce an immediate lack of consciousness; for others, consciousness is lost progressively.