B. Stunning Instruments with Captive Bolt arrangement.

STUNNING INSTRUMENTS WITH CAPTIVE BOLT ARRANGEMENT

Captive Bolt Pistol – Percussive Stunning (Click here to see the picture)

  • Many different types of captive bolt pistol/percussive stunning pistol are in use of throughput the world, having been introduced at the end of the nineteenth century.
  • They are generally operated by means of a blank cartridge, although some are pneumatic in design.
  • With the most common pistol, the captive bolt pistol, a bolt is propelled forward on discharge of the blank cartridge and automatically recoils into the barrel.
  • Ideally, the bolt should be recessed into the body of the pistol so that when the muzzle is held firmly against the animal’s head, the bolt can gain velocity before penetration of the skull occurs.
  • It is important when using captive bolt pistol to ensure that the correct strength of cartridge is used for the different species.
  • With the Cash instruments these range in strength from 1 grain for small animals such as milk lambs, up to 3 and 4 grains for large cattle and mature bulls (1 grain = 0.065 grams).
  • In most cases a 0.22 or 0.25 cartridge is used while in horses a 0.64 blank cartridge may be required for certain guns.
  • In this method three types of blank cartridges are used, viz.
    • green topped cartridges are used for larger animals (cattle),
    • black topped ones for medium sized animals and
    • red topped ones for the small sized animals (sheep).
  • Properly used, the captive bolt pistol is very effective in cattle, sheep and calves but less so in bulls and pigs, especially sows and boars, in which the frontal bone structure is very thick.
  • This penetrative type of percussive stunner produces immediate and permanent insensibility by destruction of the cortex and deeper parts of the brain, a rapid rise and then fall in intracranial pressure and the sudden jerk due to the energy the bolt imparts to the head, producing what is known as acceleration concussion.
  • These effects result in depolarization of neurons in the brain, including those of the cerebral cortex.
  • The important force in producing unconsciousness with the captive bolt pistol is the actual velocity of the bolt and the speed at which it strikes the brain, rather than the penetration of the brain per se.
  • A velocity of about 76-91 m/s is aimed at, this in practice being about 73 m/s.
  • The strength of the cartridge must be matched with the robustness of the gun to prevent metal fatigue and breaks in washers, etc.
  • The captive bolt pistol is a very useful instrument but it cannot be used for slaughter at rates of over 240-250 per hour owing to difficulties in reloading. In this case an automatically resetting gun can be used.
  • As for all forms of stunning it is vital that stunning-box design should be good. Very deep stunning boxes where the operative has to bend very low to reach the animal's head are unsuitable and require a percussion stunner with a long handle rather that the smaller instrument.
  • Pneumatic stunners, where the bolt is activated under high pressure of 80-120 psi, require somewhat complicated actions to fire them, and there may be occasions when air pressure is inadequate. With proper pressure, however, a high bolt velocity can be achieved.
  • Non-penetrative percussion stunners using a mushroom head are sometimes used in calves when brains are collected for edible use and are in regular use in the USA.
  • Properly used, this method is capable of producing immediate insensibility, which lasts for more than 30 seconds in calves.
  • It is probably not as useful in older cattle, but can be applied successfully in sheep. In young calves with thin skulls intracranial hemorrhage may occur, but the occurrence of blood splashing in muscle in sheep rarely happens.
  • In older animals, especially cattle, the method probably does not produce an adequate degree of insensibility.
  • Much depends on the operative as to whether or not blood splashing results, especially in the case of lambs.
  • If the animals are handled properly and there is no long interval between stunning and bleeding, blood splashing in muscle will be minimal.
  • In any case, the period between stunning and sticking should not exceed 30s with non-penetrative percussive stunning of cattle.
  • This compares with a recommended stun-to-sticking interval of less than 60s with penetrative percussive stunners in cattle, <15s for sheep and goats and <10s for calves.
Last modified: Wednesday, 12 October 2011, 10:32 AM