Recent methodological developments related to quantitative analysis of the electroencephalogram (EEG) allow the experience of pain to be assessed and has been applied to the question of the slaughter of calves by ventral-neck incision. The new information demonstrates clearly 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.
Gibson et al: A re-evaluation of the need to stun calves prior to slaughter, by ventral-neck incision: An introductory review, 2009
Essays on Animal slaughter and Islamic rules
Contrary to common belief, there are no explicit rules in the Koran about the method of slaughtering an animal.