Physiological Effects Of Concussion Stunning

When a fast, heavy blow is correctly applied to the skull it produces a rapid acceleration of the head, causing the brain to collide against the inside of the skull. This causes disruption of normal electrical activity resulting from a sudden, massive increase in intra-cranial pressure followed by an equally sudden drop in pressure. The resultant damage to the nerves and blood vessels causes brain dysfunction and/or destruction, and impaired blood circulation. The duration of insensibility depends on the severity of damage to the nervous tissue and the degree to which the blood supply is reduced.

The initial effect on poultry is immediate insensibility, accompanied by what is termed ‘tonic’ activity: the bird becomes rigid, reflexes are lost and rhythmic breathing stops. This is quickly followed by the ‘clonic’ phase during which the bird will display pronounced, uncontrolled movement, especially of the wings. If poultry are concussion-stunned in the correct position with sufficient force, the stun is usually irreversible. However, if insufficient force is delivered, or the positioning is incorrect, the bird may recover to some degree. If there is any uncertainty as to whether a bird has been effectively stunned, it should be re-stunned immediately.

An effective stun can be defined as one that causes immediate insensibilty. This condition should persist until death.