Stunning is the process of rendering animals immobile or unconscious, with or without killing the animal, when or immediately prior to slaughtering them for food. Rationale Within the European Union, most animals slaughtered for human consumption are killed by cutting major blood vessels in the neck or thorax so that rapid blood loss occurs. After a certain degree of blood loss has occurred, the animal will become unconscious, and after a greater blood loss death will ensue. From the moment of cutting until the loss of consciousness, the animal experiences pain, stress, and fear. Without stunning, the time between cutting through the major blood vessels and insensibility, as deduced from behavioural and brain response, is up to 20 seconds in sheep, up to 25 seconds in pigs, up to 2 minutes in cattle, up to 2.5 or more minutes in poultry, and sometimes 15 minutes or more in fish. If one seeks to minimise animal suffering in slaughter, stunning is necessary. The best stunning method depends on the species; the quality of equipment and the adequate training of personnel also influence effectiveness. History 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 slaughter pistols and electric stunners, pigs, sheep, and other animals (including cattle) were simply struck while fully conscious. The belief that it was unnecessarily cruel to slaughter an animal against its will 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 supposedly painlessly and without their knowledge, and he founded the Model Abattoir Society in 1882 to investigate and campaign for other 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 stunning by many