Amelioration of electroencephalographic responses to slaughter by non-penetrative captive-bolt stunning after ventral-neck incision in halothane-anaesthetised calves

Abstract

AIM: To investigate the ability of non-penetrative captive-bolt stunning delivered after ventral-neck incision to ameliorate responses to noxious stimulation associated with slaughter by ventral-neck incision in halothane-anaesthetised calves.

METHODS: Seven calves were minimally anaesthetised with halothane, using an established anaesthesia protocol. Electroencephalographic (EEG) indices of cerebrocortical activity were measured in response to ventral-neck incision followed 5 seconds later by non-penetrative captive-bolt stunning. Changes in heart rate and arterial blood pressure were measured and instances of occlusion of the carotid arteries were also noted.

RESULTS: After ventral-neck incision there were periods of an active EEG in some calves, which ceased after non-penetrative captive-bolt stunning in most of the animals. Two calves had periods of active EEG following stunning. Arterial blood pressure decreased signifi cantly after neck incision in all calves, including three with occlusion of the carotid arteries.

CONCLUSIONS: Non-penetrative captive-bolt stunning after ventral-neck incision resulted in the cessation of functional cortical activity in the majority of calves. This procedure prevented the development of cerebrocortical responses to ventral-neck incision, demonstrated elsewhere, which would be painful in conscious animals subjected to this procedure. In addition, instances of carotid arterial occlusion had no significant effect on the decrease in arterial blood pressure.

KEY WORDS:

• Calves
• compressed spectral array
• concussive stunning
• electroencephalogram
• minimal anaesthesia
• non-penetrative stunning
• slaughter

Acknowledgement

The authors would like to thank Corrin Hulls, Leanne McCracken, Neil Ward, Mike Hogan, and members of the Large Animal Teaching Unit and the Small Animal Production Unit, Massey University, for assistance during the experiment. This study was jointly funded by the Department for Environment, Food and Rural Affairs of the United Kingdom and the Ministry of Agriculture and Forestry of New Zealand. TJ Gibson was the recipient of a C Alma Baker Postgraduate Scholarship.