Electrical stunning and stillness of lambs.

The stillness obtained with head-to-back stunning results from the current depolarizing spinal neurones. The same effect can be achieved by sequentially applying a head stun, followed by a current through the heart to stop it and a current down the spinal cord to abolish movement. The level of speckle bruising for this sequential stun is lower than that associated with head-to-back stunning and is similar to that of head-to-foreleg stunning. After head-only stunning, current passed continuously down the spinal cord through a good contact at voltages around 40 V gave adequate stillness, which improved when the voltage was raised to 80 V. With a frequency of 14 Hz, 40 V presented no hazard to workers. After head-only stunning, a brief application of current down the entire spinal cord for 2-4 s at 110 V or greater also effectively suppressed movement. With legs as contact points voltages as high as 400 V were necessary. For effective animal stillness good electrode contact is necessary and electrodes should be placed as close to the spinal cord as possible. With a continuous current flowing the oesophagus remained closed until muscle exhaustion occurred; even with a brief current down the spinal cord, the oesophagus remained closed for at least 30 s. Low voltage stimulation in the form of a continuous current cannot replace high voltage stimulation, but can supplement it, and therefore could be incorporated into the electrical stimulation process. Head-only stunning, followed by a cut through the major blood vessels of the neck, is acceptable for Halal slaughter and is now in use commercially in New Zealand. Subsequent movement is suppressed by a spinal discharge at 400 V using leg contacts.