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

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 significantly 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.