Electroencephalographic studies of stunning and slaughter of sheep and calves- Part 3: The duration of insensibility induced by electrical stunning in sheep and calves.

The duration of insensibility produced by electrical and percussive stunning was studied in sheep and calves. Insensibility was determined from the study of electroencephalograms (EEG) and concurrent observations were made of the reflexes and reactions of the animals. The effect of stunning on the circulation was assessed from electrocardiograms (ECG) and femoral blood pressures (BP). Electrical stunning of sheep by electrodes to the head only produced a period of reversible insensibility of 18-42s. This technique also caused an immediate and prolonged increase in BP. Electrical stunning of both sheep and calves by a 'head to back' method, which causes concurrent cardiac dysfunction, produced immediate and permanent insensibility associated with cessation of circulation and an immediate drop in BP. The use of a non-penetrative method of percussion stunning caused immediate insensibility and an increase in BP which persisted after exsanguination had commenced. Calves stunned with a penetrating captive bolt showed immediate and permanent insensibility and the EEG became isoelectric within 15 s.