Stunner (cattle)
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Stunners (aka "knocker, knock bolt, bolt gun) is the device used to render red meat animals unconscious prior to further slaughter procedures such as sticking(bleed out), skinning, removal of hooves.
Animals are driven from the lairage to the stunning chute or restrainer. There, at the restrainer, the red meat animal is stunned using the captive bolt stunner. Captive bolt stunners are driven by pneumatic (compressed air) or by cartridge. Depending if the plant is saving brains for human consumption (only done in veal plants, no longer is it done with beef, goats and sheep due to BSE and other prion disease consumption) will a concussive stunner be used. The bolt doesn't enter the skull,it stuns and renders the animal unconscious by extreme concussive force. If the brains aren't destined to be saved for human consumption, then a penetrating stunner is used. Penetrating stunners stun by driving a stainless steel rod into the skull. This stuns the animal by lowering rapidly the pressure around the brain and obliterating the brain tissues of the higher brain, but not damaging the brain stem, which controls the heartbeat which is needed to ensure an efficient bleed.
Captive bolt stunners are safer to use in most red meat slaughter situations. There is no danger of ricochet or overpenetration as there is with regular firearms.
Captive bolts allow for meat trimming from the head to be salvaged.
Effective stunning requires the operator to wait until the animal turns its head towards him or holds still. The operator should not attempt to "chase" the animal's head to stun, as such a stun may not always be effective in rendering the animal unconscious.
Most animal are stunned at a place on the forehead or pate above the eyes. To visualize the stunning area, draw an imaginary cross above the eyes and below the ears in the middle of the forehead. Some animals (old Hereford cattle---too much hair on forehead/pate)and bulls---too thick of skull)are stunned at the back of the poll. This is known as poll knocking. It can render livestock unconscious, but may require more attempts since the placement of the bolt is harder (place the bolt in the space where the skull meets the head in the depression that it makes)
