Animal slaughter

Animal slaughter is the killing of animals, usually referring to killing domestic livestock. It is estimated that each year, 80 billion land animals are slaughtered for food. Most animals are slaughtered for food; however, they may also be slaughtered for other reasons such as for harvesting of pelts, being diseased and unsuitable for consumption, or being surplus for maintaining a breeding stock. Slaughter typically involves some initial cutting, opening the major body cavities to remove the entrails and offal but usually leaving the carcass in one piece. Such dressing can be done by hunters in the field (field dressing of game) or in a slaughterhouse. Later, the carcass is usually butchered into smaller cuts.

The animals most commonly slaughtered for food are cattle and water buffalo, sheep, goats, pigs, deer, horses, rabbits, poultry (mainly chickens, turkeys, ducks and geese), insects (a commercial species is the house cricket), and increasingly, fish in the aquaculture industry (fish farming). In 2020, Faunalytics reported that the countries with the largest number of slaughtered cows and chickens are China, the United States, and Brazil. Concerning pigs, they are slaughtered by far the most in China, followed by the United States, Germany, Spain, Vietnam, and Brazil. For sheep, again China slaughtered the most, this time followed by Australia and New Zealand. Similarly, the amount (in tonnes) of fish used for production is highest in China, Indonesia, Peru, India, Russia, and the United States (in that order).

The use of a sharpened blade for the slaughtering of livestock has been practised throughout history. Prior to the development of electric stunning equipment, some species were killed by simply striking them with a blunt instrument, sometimes followed by exsanguination with a knife.

The belief that this was unnecessarily cruel and painful to the animal eventually led to the adoption of specific stunning and slaughter 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 a result of attempting to discover and adapt substances capable of producing general or local anaesthesia to relieve pain in people. As early as 1853, he designed a chamber that could kill animals by gassing them. He also founded the Model Abattoir Society in 1882 to investigate and campaign for humane methods of slaughter and 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, or HSA) was established in England to improve the slaughter of livestock. 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 went on to play 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.^{[citation needed]}

Various methods are used to kill or render an animal unconscious during animal slaughter.

Whether animals are stunned before slaughter or not, they suffer stress while waiting to be killed. A 1996 veterinary review found that there are many ways in which animals suffer and die during the preslaughter period. They include: