Stunning can be accomplished with gas, electricity or physical concussion. In the past, farm animals were sometimes stunned by a heavy blow with a blunt instrument on the front of the head. Some western European towns had legal requirements for concussion stunning as early as the eleventh century. However, by the end of the nineteenth century, most animals were not stunned before slaughter. Concerns about animal welfare grew during the twentieth century, particularly from the 1960s, and it was eventually agreed that concussion stunning was unsatisfactory.

Stunning methods have improved over a long period. Stunning by captive bolt was introduced at the end of the nineteenth century (Breidert, 1902), electrical stunning at the end of the 1920s (Raschke, 1928) and CO2 stunning in the 1950s (Wernberg, 1957).

Group handling and stunning of pigs is an improvement compared to the handling of solitary slaughter pigs . This is an example of a technical solution based on the behaviour of animals. Photo: Anne Algers