Stun Duration

The purpose of stunning an animal is to make it insensible to pain until death is caused by bleeding or cardiac arrest. Therefore, it is important to know the duration of an effective electrical stun. The tonic and clonic phases of a stun have already been described. Table 2 gives the time in seconds that these phases are expected to last (these times relate to the recommended minimum application of stunning currents).

Table 2 Expected duration of phases following head-only electrical stunning

It is also important to know the duration of unconsciousness when calculating the maximum interval between stunning and bleeding, in order to avoid the risk of animals recovering consciousness before they die from loss of blood. Table 3 lists the average time span in seconds to loss of brain function following various bleeding methods. Where death is not induced by cardiac arrest, all stunned animals must be bled within 15 seconds of stunning. (N.B. These are average times, actual times to loss of brain function may vary from these figures and be greater or less)

Table 3 Mean time to loss of brain function following various bleeding methods

Not only must animals be bled without delay, but correct procedures must also be followed. The following diagram (Figure 4) shows the variation in times to loss of brain function, as influenced by the timeliness, quality and techniques of sticking. For example, in sheep, if only one carotid artery and one jugular vein are cut (half cut), brain death can take up to 70 seconds (over 50 seconds longer than a full cut). After this length of time the animal will be in the recovery phase and may no longer be insensible to pain. The diagram also shows the increased likelihood of pigs regaining consciousness before dying, if chest sticking is delayed. The section on bleeding describes the correct sticking procedures to ensure that these times are achieved.

Figure 4 Relationship between the phases of epilepsy and the importance of quick and effective stunning

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