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Medieval pig stunning using a pollaxe.

Stunning is the process of rendering animals immobile or unconscious, without killing the animal, prior to their being slaughtered for food.


This process has been common for centuries in the case of cattle, which were poleaxed prior to being bled out. In the United Kingdom and Europe more widely the development of stunning technologies occurred largely in the first half of the twentieth century.

Prior to humane slaughter pistols and electric stunners, pigs, sheep and other animals (including cattle) were simply struck while fully conscious. The belief that this was unnecessarily cruel and painful to the animal being slaughtered led to the compulsory adoption of stunning methods in many countries. The Humane Slaughter Act of 1933 in Britain, for example, was specifically conceived not only to make stunning compulsory, but moreover to make modern methods, such as the captive bolt pistol and electric tongs, the means by which it was achieved. The wording of the 1933 act specifically outlaws the poleaxe. The period is marked by the development of various innovations in slaughterhouse technologies, not all of them particularly long-lasting.

Modern methods[edit]

In modern slaughterhouses a variety of stunning methods are used on livestock. Methods include:

  • Electrical stunning
  • Gas stunning
  • Percussive stunning

Electrical stunning[edit]

Electrical stunning is done by sending an electrical current through the brain and/or heart of the animal before slaughter. Current passing through the brain induces an immediate but non-fatal general convulsion that produces unconsciousness. Current passing through the heart produces an immediate cardiac arrest that also leads shortly to unconsciousness and death. It is a controversial subject however. With chickens for example, overstunning leads to bone fractures and/or electrocution which prevents bleeding of the animal. This negatively affects the quality of the meat, and therefore understunning is an attractive practice for slaughterhouses.

In the Netherlands, for example, the law states that poultry must be stunned for 4 seconds minimum with an average current of 100 mA, which leads to systematic understunning.

The CrustaStun is a device designed to administer a lethal electric shock to shellfish (such as lobsters, crabs, and crayfish) before cooking. This avoids boiling a live shellfish which may be able to experience pain in a way similar to vertebrates. The device works by applying a 110 volt, 2–5 amp electrical charge to the animal. It is reported the CrustaStun renders the shellfish unconscious in 0.3 seconds and kills the animal in 5 to 10 seconds, compared to 3 minutes to kill a lobster by boiling or 4.5 minutes for a crab.[1][2]

Gas stunning[edit]

With gas stunning animals are exposed to a mixture of breathing gases (carbon dioxide for example, but historically carbon monoxide was used) that produce unconsciousness or death through hypoxia or asphyxia. The process is not instantaneous.

Percussive stunning[edit]

With percussive stunning, a device which hits the animal on the head, with or without penetration, is employed. Such devices, such as the captive bolt pistol, can be either pneumatic, or powder-actuated. Percussive stunning produces immediate unconsciousness through brain trauma.


United States regulation[edit]

Stunning is regulated by the provisions of the Humane Methods of Slaughter Act (7 U.S.C. 1901), which the Food Safety and Inspection Service (FSIS) is mandated to uphold under the Federal Meat Inspection Act (21 U.S.C. 603 (b)). No similar provision exists in the Poultry Products Inspection Act of 1957 (21 U.S.C. 451 et seq.). After confirmation of the first U.S. BSE case, FSIS issued regulations (69 FR 1887, January 12, 2004) prohibiting the use of the most widely used stunning device (air-injection captive bolt stun gun) because the compressed air (in contrast to the blank cartridge-driven or non-penetrating captive bolt) has been shown to force pieces of brain and other central nervous system (CNS) tissue into the bloodstream. Cattle blood is processed primarily for use as a protein supplement in animal feeds and milk replacer for calves, and could potentially transmit BSE if it contained specified risk materials (SRMs include brain and CNS tissue).[3]

See also[edit]


External links[edit]