Pig slaughter
Slaughter of pigs is mainly done in large slaughterhouses around the country. Pig slaughter consists of a long series of processes; they are described below:
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You can learn more about automation at the slaughterhouses under the theme "Robots on the slaughterline" On Danish Crown's homepage you can see an exposition of the different processes at the slaughterhouse. |
Transport and lairage
When a farmer is ready to supply pigs for slaughter, he contacts the slaughterhouse about a week before and tells how many pigs he expects to supply. This provides time for the slaughterhouse to plan collection and slaughter. The day of collection by the haulage contractor, or the previous day, he moves the pigs to a special delivery room, which is separated from the other production. The reason is to avoid that the transport driver, who might have other pigs on the lorry, transfers infection to the herd.
It is most common for the slaughterhouse to plan the collection of the pigs. The transport is done by private haulage contractors, but the slaughterhouse will normally plan the route to ensure that the pigs spend as short time as possible on the lorry. Nearly all Danish slaughter pigs spend less that three hours from the farm to the slaughterhouse - the transport will typically last 1-1 1/2 hours. This is far less than the maximum allowed transport time. According to the regulations animals may be transported for up to eight hours before they are fed and watered.
The pigs are transported to the slaughterhouse in special lorries with slip proof flooring, ventilation and division into compartments so that pigs from different herds do not fight. A few farmers choose to deliver the pigs themselves.
At the slaughterhouse the pigs are driven out of the vehicles and checked by a veterinary surgeon to ensure that they are healthy; they are then driven to the lairage pens.
Stunning and sticking
After a couple of hours in the pens the pigs are driven to stunning. They are stunned with carbon dioxide (CO2) by being driven into a 'lift', which subsequently is lowered into a pit with carbon dioxide. The pigs become unconscious by breathing the carbon dioxide. The unconscious pigs are lifted up in a hind leg and conveyed to be stuck in the neck artery and die. They are often stuck with a special hollow knife with a hose attached, so that the blood is collected automatically via the knife. The blood is later centrifuged to separate it into plasma (ca. 60%) and haemoglobin, which are both frozen. The total blood is used directly for the manufacture of blood pudding and sausage, but the blood plasma is used as an ingredient for a number of products. The haemoglobin part (red) is used for example as mink feed.
Unclean slaughterline
After stunning and sticking the first part of the process is the unclean section where the carcasses are scalded. They are pulled through a long vessel with warm water (61oC) where the hairs are loosened. The scalding can also be done with steam; then the carcasses are conveyed through a cabinet, while hot water vapour is blown over them.
The carcasses are then going through the dehairer, where hair and hooves are removed while the carcass passes between two cylinders.
After the dehairer the carcasses are transferred to gambrels with the ends going through each hind leg so the carcass hangs with its head downward. Each gambrel has a number, for example a bar code, a radio chip or a steel plate with punched numbers, which automatically records when the carcass moves through the different processes on the slaughterline.
The carcass is then singed in a kiln with flames that carbonise the outer skin layer. This removes any remaining hairs and contributes to giving the skin the correct texture.
The next stage is the rind treatment, where the black rind from the singeing is scraped off. This is done in several stages - first by the so-called black scraping, which removes the majority, followed by a further scraping and brushing to clean the carcass all over.
The carcass is now ready in the 'unclean' part of the slaughterline and is transferred to the 'clean' part.
Clean slaughterline
The first thing that happens here is that the carcass is 'opened' i.e. cut open with a perpendicular ventral cut. The thorax bone is sawn through so that the carcass is open at the front. The viscera are taken out and divided into pluck (i.e. tongue, oesophagus, heart, lungs, liver and diaphragm) plus stomach and intestines. The viscera are conveyed parallel with the carcass to the veterinary meat inspection.
The carcass is split. First it is cut from the dorsal side at both sides of the spinous processes of the backbone (called 'free cutting'); then it is split with a saw into two halves along its length through the backbone and chest to be joined by the snout only.
The carcass and the viscera are then checked by a veterinarian to ensure that the meat if free of disease. If there is sign of disease, the diseased parts are partly or completely condemned depending on the type of disease. Approved stomachs and intestines are sent to the casing cleaning department, and the other approved parts are being chilled.
Then the carcass is weighed. The supplier's number (i.e. the farmer's number) is registered on a computer together with the carcass weight (carcass without blood and viscera).
Then the carcass is classified and is ready for carcass chilling.
Classification and payment
In the classification the lean meat content is measured in each carcass. The meat content ('meat percent') is, in combination with the carcass weight, the basis for the payment to the farmer. He is paid according to the number of kg lean meat in the carcass. Each week the slaughtethouse companies determine their basic price per kg pig meat.
Measurement of the lean meat content in the carcasses has hitherto been done in a special 'classification centre' where probes are inserted into the carcasses and measure - via light reflection - certain fat and meat thicknesses. Based on these measurements the meat percent is calculated for the carcass and for the major cuts. A new equipment for classification, which is based on ultrasound measurements, has been implemented at one slaughterhouse. The advantage is that the measurement can be done without penetrating the carcass.
The farmer gets the basic price for the pig if the carcass has the basic lean meat content (today 60%) and is within a certain weight interval. If the meat content is lower than the basic, there is a deduction from the payment, and if it is higher, the payment is increased up to 65%, where the payment is not increased further.
If the carcass weight is lower or higher than the optimum interval (typically between 67 and 81-82 kg) there is a gradual reduction in the payment.
If the farmer produces special pigs (for example pigs with a special good eating quality or ethical quality) he gets a special addition to the basic price.
The slaughterhouses determine the criteria for payment according to the qualities required by the markets. It is important for the farmers to supply the pigs for slaughter when the meat content and carcass weight is at the optimum level in order to achieve maximum payment.
Once a year the slaughterhouses pay an additional 'after-payment' to their members; this means that the annual profit is distributed according to the carcass weight supplied.
Health stamps
The last process is to apply health stamps onto the carcasses to certify that they have been checked and to be able to trace back in case of problems.
Meat from slaughterhouses authorised for export, i.e. slaughterhouses fulfilling especially high hygiene requirements, will be stamped with oval stamps (at least 6.5 x 4.5 cm), which among other things show the plant's authorisation number. Meat from plants not authorised for export ('home market plants') are marked with a round stamp, which also contains the authorisation number of the plant.
In addition to the official health stamps, the plants often apply their own quality stamps, for example for the selling classes that are marked [A1], A1, A and B.
Chilling
When the slaughter processes of the carcass have been completed, it has to be chilled. The temperature of the carcass is approximately 30oC after slaughter, and it must be chilled to a temperature below 7oC within 24 hours.
The purpose of the carcass chilling is to arrest the bacterial development in order to improve the shelf-life and safety of the meat. The chilling also contributes to a reduction of the evaporation, so that the carcasses do not lose so much weight.
At the start of the chilling the carcasses are conveyed through the blast tunnel - a long corridor where very cold air (between -20 and -30oC) is blown onto the carcasses to provide rapid cooling. The surface is actually frozen while the interior is still warm.
After the chilling tunnel the carcasses are taken into a chill room at a temperature of 5oC. They hang here while the temperature in the muscles and the carcass equilibrates to a maximum of 7oC in the interior.
It is often discussed whether the powerful chilling in the blast tunnel results in a poorer meat quality than a slower chilling in a chill room. Several investigations, e.g. by the Danish Meat Research Institute, have shown, however, that meat chilled correctly in a blast tunnel is at least as good as other meat.
The day after slaughter, when the carcass has been cooled, it will be cut. First the head and feet are cut off - this completes the separation of the carcass into its two halves. Each of the carcass halves is then cut into three parts: Fore-end, middle and hind leg. The middle is often cut into loin and belly.
These primal cuts constitute the basis for the further cutting and boning of the meat according to the customers' specifications.
The Danish pig meat export consists mainly of fresh (chilled) or frozen cuts. The fore-ends are for example sent to
The cuts are mainly used for further processing in the import countries; for example into cured and cooked meat products.
Processing
Part of the pig meat is used for various processed meat products; for example bacon, cold cuts, sausages, cooked hams and various types of canned meats. Read more under processing.
Hygiene
A good hygiene is a prerequisite for healthy products of good quality. The hygiene is influenced by many factors during slaughter, chilling, cutting, boning, processing, retailing and storage in the consumer's home. All links in this chain must understand the necessity of good hygiene.
Basically hygiene is to avoid contamination of the meat with undesired bacteria and to avoid growth of microorganisms. Hygiene is also aesthetics/appetising conditions. Few people will accept that food is made or handled in unappetising conditions.
Living animals have a natural flora of microorganisms on the skin, in the nose, pharynx, intestinal tract and around anus and the genitals. Muscles and organs are, on the contrary, normally sterile. Microorganisms can occur in blood and tissues during infections, but the body's immune defence will normally combat them.
During slaughter the interior of the carcass will be contaminated due to cutting and handling. Knives, saws and other equipment transfer microorganisms from the surface to the interior of the carcass. Contamination of the meat with bacteria from the pharynx and intestines, where pathogens can occur, is particularly critical. Continuous disinfection of knives and equipment, careful handling of the carcasses during the different slaughter processes and effective chilling are preconditions for a good hygiene with minimum microbiological contamination of the meat. It is not possible completely to avoid bacteria on the meat. However, the bacteria are only on the surfaces of the meat - not inside the muscles.
During cutting and boning further bacteria are transferred to the meat from the equipment and the handling of the products. The shelf-life is reduced because many new surfaces are created. Particularly when the meat is minced, where the surface is increased a lot and good conditions are created for bacterial growth.
Bacterial activity, and thus the quality and shelf-life of the products, is first and foremost controlled by the temperature. An unbroken chain of refrigeration, i.e. a constant low temperature during production, storage, distribution and holding in the shop and at the consumers' homes is a precondition for maintaining a good quality and obtaining a reasonable shelf-life of the meat.
Control
The control of hygiene and health is done by the public veterinary inspection and by the slaughterhouse. Read more about the control under food safety.
