Mechanical, electrical or gas stunning; slaughter methods and monitoring signs of unconsciousness or consciousness
Introduction: pre-slaughter stunning
The outcome of stunning prior to slaughter is to render the animal unconscious such that it is insensible to any pain and distress associated with the cutting and bleeding out slaughter activity. Despite this beneficial outcome of avoidable suffering and pain, nevertheless, stunning is a universally recognized slaughter activity that carries a substantial animal welfare risk. Not only can the stunning method itself cause suffering if ineffectively done, it can result in the completely unacceptable situation where a still conscious animal is exposed to further dressing procedures that will cause it great anguish before it dies.
Stunning methods may be irreversible which means the animal will not regain consciousness although the heart may still be beating. By contrast, reversible stunning methods will allow the animal to regain consciousness and these rely on the bleeding out stage from cutting the blood vessels to result in the death of the animal.
Stunning should fulfill the following requirements in order to demonstrate the outcome of avoidable suffering to the individual food animal:
- The animal should remain in a state of unconsciousness that extends beyond the time required to use a neck cut to bleed the animal that results in death
- The stunning method should result in minimal signs of distress in the animal before the loss of consciousness
Assessing the state of unconsciousness in the stunned animal is not always a straightforward task. The definitely conscious will be clearly distinguishable from the definitely unconsciousness (including brain dead) by observation of well documented signs associated with these states. However there is a transition zone or a gray zone between consciousness and unconsciousness when the animal may slide into and out of consciousness that may require re-stunning the animal to avoid a return to consciousness.
There is the risk for any stunning method to fail; however with well trained and qualified staff, equipment used according to the manufacturer's specifications and which is always kept well maintained, these risks should be controllable to the point that the outcome of avoidable suffering can be achieved.
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