A re-evaluation of the need to stun calves prior to slaughter by ventral-neck incision: An introductory review

Abstract

Commercial slaughter of farm livestock usually employs an extensive incision that severs the soft tissues of the neck including the major blood vessels supplying and draining the brain. It is intended to cause a catastrophic decrease in cerebral blood fl ow with rapid onset of unconsciousness or insensibility. The tissues of the neck are innervated with nociceptive nerve fi bres and their transection will cause a barrage of sensory impulses. Consciousness, and therefore the ability of the animal to feel pain and experience distress after the incision, may persist for 60 seconds or longer in cattle. These observations suggest that livestock may experience pain and distress during the period before they become unconscious (insensible). Psychological shock and fear may also be associated with the extensive tissue damage and blood loss. Pre-incision stunning has been adopted as a precautionary measure to prevent suffering. However, the question remains: How intense and noxious are these experiences? Recent methodological developments related to quantitative analysis of the electroencephalogram (EEG) allow the experience of pain to be assessed more directly than has hitherto been possible. This methodology has now been applied to the question of the slaughter of calves by ventral-neck incision. The new information demonstrates clearly for the fi rst time that the act of slaughter by ventral-neck incision is associated with noxious stimulation that would be expected to be perceived as painful in the period between the incision and loss of consciousness. These data provide further support for the value of stunning in preventing pain and distress in animals subjected to this procedure.

KEY WORDS:

• Calves
• distress
• insensibility
• nociception
• pain
• pre-incision stunning
• slaughter
• ventral-neck incision

Acknowledgements

We are grateful to the Department for Environment, Food and Rural Affairs (DEFRA, United Kingdom) and the Ministry of Agriculture and Forestry (MAF Biosecurity, New Zealand) for fi - nancially supporting this programme, and to Drs David Pritchard and Kirk Thompson (DEFRA) and Dr David Bayvel (MAF) for contributions to experimental design during the planning stage. We are also grateful for the input of three anonymous international referees who commented on the four manuscripts before their submission to the New Zealand Veterinary Journal and its full peer-reviewing process. TJ Gibson was the recipient of a C Alma Baker Postgraduate Scholarship.