A slaughterhouse also called an “abattoir”, is a facility where animals are killed and processed into meat products. In large facilities, slaughtering is carried out in fully mechanised lines. The workers are assigned to specific workstations and the carcasses move on a conveyor system from station to station until the slaughter process is completed.
In slaughter line operations, clean and unclean operations are physically separated and individually manned to avoid contamination of carcasses and edible by-products. The unclean operations include stunning, bleeding, and defeathering (poultry), dehairing (pigs) and dehiding (cattle and small ruminants). The clean operations include evisceration, carcass splitting and carcass dressing.
In many developing countries adequate slaughter facilities are not available. At rural or local level slaughtering is often either carried out under a tree or in deteriorated and outdated slaughter units without any waste treatment facilities. This often results in health hazards through contamination of the meat during slaughter operations and of the surrounding land and water through uncontrolled release of waste and effluents.
In rural settings slaughtering can be done in basic small-scale facilities. Before building a slaughtering facility a number of factors must be considered including the species to be slaughtered, expected slaughter numbers, environmental impact, the availability of a competent workforce and the linkages to the meat markets.
To facilitate the efforts of governments and private investors to improve meat hygiene, the FAO/WHO Codex Alimentarius committee on meat hygiene has developed guidelines in the “Code of Hygienic Practices for Fresh Meat” on the design, facilities and equipment of slaughter establishments. FAO has also published a number of technical papers dealing with the issue.
In many developing countries, lack of appropriate slaughtering facilities and unsatisfactory slaughtering techniques are causing unnecessary losses of meat as well as valuable by-products from animal carcasses. Therefore adequate facilities, clearly defined working procedures and well-trained skilled labour are essential to guarantee a safe supply of wholesome meat.
Slaughter process diagram
In cattle slaughter commonly mechanical stunning (penetrative and non-penetrative) with a captive bolt pistol is used. Electrical stunning is increasingly an option. This is followed by bleeding in a hanging position. In smaller operations, the carcass is lowered onto a cradle, head and feet are removed and flaying (removal of skin) initiated. Then the carcass is raised again and flaying completed. In bigger operations, carcasses remain suspended on overhead rails and hide pulling devices are used to reduce contamination of the carcass surface. After flaying, evisceration takes place. White and red offal are separated, inspected and cleaned. Condemned material is separated and disposed of in a sanitary manner. The slaughter procedure for small ruminants is similar to that of cattle.
Poultry slaughter in larger operations, the birds are suspended by the leg on solid wire shackles attached to a conveyor system taking them to the various workstations. The birds are stunned prior to bleeding and then passed through either scalding water or a steam tunnel and through rotating devices with rubber scrubbers to remove feathers. After chilling the birds in iced water, evisceration takes place. In smaller operations, the birds are usually fixed in cones for bleeding, scalded in hot water and defeathered either manually or by use of a drum plucker. They are then eviscerated and chilled.
In pig slaughter electrical stunning is commonly used (carbon dioxide gas is an option). In smaller operations, the pig is hoisted for bleeding. After bleeding, the carcass is lowered into the scalding tank filled with water at around +60°C (140°F). After a few minutes, the carcass is removed and the hair is scraped off manually. After dehairing, the carcass is usually exposed to open gas flames to remove remaining hair and reduce surface contamination. The carcass is then transferred to the overhead rail where final cleaning takes place, followed by evisceration. The internal organs are inspected and cleaned for further use. The carcass is split and inspected and either chilled or directly dispatched. In larger operations pigs move on conveyor systems through scalding tunnels and dehairing machines with rotating rubber fixtures.