An extract on #stunning
A primitive form of stunning was used in premodern times in the case of cattle, which were poleaxed prior to being bled out. However, 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 eventually led to the compulsory adoption of stunning methods in many countries. One of the first campaigners on the matter was the eminent physician, Benjamin Ward Richardson, who spent many years of his later working life developing more humane methods of slaughter. As early as 1853, he designed a lethal chamber that would gas animals to death relatively painlessly, and he founded the Model Abattoir Society in 1882 to investigate and campaign for humane methods of slaughter. He even experimented with the use of electric current at the Royal Polytechnic Institution.
The development of stunning technologies occurred largely in the first half of the twentieth century. In 1911, the Council of Justice to Animals (later the Humane Slaughter Association) was created to improve the slaughter of livestock and address the killing of unwanted pets. In the early 1920s, the HSA introduced and demonstrated a mechanical stunner, which led to the adoption of humane stunning by many local authorities."
The HSA played a key role in the passage of the Slaughter of Animals Act 1933. This made the mechanical stunning of cows and electrical stunning of pigs compulsory, with the exception of Jewish and Muslim meat. Modern methods, such as the captive bolt pistol and electric tongs were required and the Act's wording specifically outlawed the poleaxe. The period was marked by the development of various innovations in slaughterhouse technologies, not all of them particularly long-lasting.
Electrical stunning is done by sending an electric 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, 25 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.