In the slaughterhouse
Like farming, slaughter is an industrial process designed to minimise the time taken to turn living animals into meat and by-products. Today, abattoirs are highly mechanised and many abattoir workers are still paid on piece work, ie by the number of animals they kill and butcher. Over two-and-a-half million animals are slaughtered in Britain’s 350 abattoirs each day, a rate that works out at around 25 per second. Clearly, the speed and “efficiency” of this process favours neither vigilance, thoroughness or care .
Numerous opportunities for contamination or the spread of disease arise in the slaughterhouse – and the consequence is that even animals free of infection when they enter the slaughterhouse may leave it as infected meat. Animals from many different farms pass through each abattoir, increasing risk of cross-contamination of equipment. Frequently covered in filth from the transport lorry, animals are supposed to be clean at slaughter but a superficial hosing down is likely to be the very most that dirty animals receive – and that may even spread infection. There is also nothing, of course, to prevent animals from defecating and contaminating themselves and others after any cleaning has taken place. In 2002/3, 128 sheep and 52 cattle were rejected at abattoirs by official vets (see below) for being too dirty  but no chickens, despite the fact that they outnumber sheep and cattle by forty times, are the main source of salmonella and campylobacter infections and, as we know, they live and are transported in the most unhygienic conditions.
All animals are also supposed to be inspected by the official vet to guarantee their health but on average, each vet is responsible for over 6,000 animals per day.  Clearly, only the most superficial examinations can be undertaken and the consequence is that only the most apparent illnesses are diagnosed. Any animals showing minimal symptoms or none will almost certainly pass the inspection process.
Prior to slaughter, animals are stunned using either the captive-bolt pistol (in cattle), electricity or (more rarely) gas. In the case of poultry, the electric shock is usually administered using an electrified water bath: birds are hung upside-down on the mechanised slaughter line and the line dips their heads into the bath as it passes over it. The bath inevitably becomes fouled with excrement, contaminating birds as they come through.
After stunning, animals are bled to death by cutting their throats as they are suspended upside-down. Larger animals will drain copious amounts of blood, contaminating clothing, equipment, walls and floors. Although blood is unlikely to harbour bacterial infection in healthy animals, animals with infection will undoubtedly face slaughter and blood stains and splashes provide a medium for bacterial growth in the slaughter area. After bleeding, many animals are immersed in scalding tanks to loosen hair and feathers – vats of hot water which inevitably become fouled with blood, dirt and excrement, forming a medium for bacterial transmission and multiplication.
Witness Statement. A visiting journalist describes the scalding tank in a chicken slaughterhouse:
“It was 3pm and, as at many factories, the water was only changed once a day. It was a brown soup of faeces and feather fragments, and, the hygiene inspector pointed out, ‘the perfect temperature for salmonella and campylobacter to survive and cross-contaminate the birds’.” The Ecologist 
Following the scalding tank, animals are butchered, the first stage of this being disembowelling. In the case of poultry this process is performed automatically by a machine but the gutting ‘spoon’ is not sterilised between animals. In larger animals, an incision is made in the belly by a slaughterman and the intestines hauled out by hand: all animals’ guts are host to huge populations of bacteria and intestinal contents may easily contaminate the flesh at this stage. So toxic are these parts of the body that an abattoir worker died recently when he was overcome by fumes clearing out a tank blocked with entrails.
Specified Risk Material (or SRM) is also removed during butchery. These are the parts of cattle, sheep and goats which are thought to carry BSE/CJD: brains, spinal cords and parts of the intestines and skeleton. If this procedure is not carried out efficiently then there is a risk of contamination of the “meat” portions of the carcase – something which undoubtedly still takes place. Remarkably, despite the rules, the supervision and the known risks, entire spinal cords are still occasionally being left in place in abattoirs in the UK, while over a hundred and twenty breaches of the SRM rules were uncovered in imported meat in 2003.
Once the animal has been butchered for meat and the edible offal removed, about half of it is still left. Little is wasted, however. Once the carcase has been manually butchered, plenty of meat is still attached to the bone and this can be harvested by blasting the bones with high pressure water, producing what is known as mechanically-recovered meat - or MRM. Effectively a meat slurry, it is usually strained through mesh to remove bone fragments and then used as a generic ‘meat’ ingredient in low-cost products. MRM from sheep and cattle has been banned as a consequence of BSE but it is still derived from pigs and poultry.
The remaining portions of the carcase still have considerable value. Gelatine is produced from animal bones, hooves, skin and connective tissue (like tendons) and used in products ranging from sweets to low-fat yoghurts to photographic film. The skin of some animals goes for leather while feathers may be used for soft furnishing (UK slaughterhouses produce 150,000 tonnes of feathers per year). Pet food manufacturers take a proportion of offal and also some of the products of the final stage in processing – rendering. Rendering essentially takes what’s left of the carcase, including feathers, some organs, heads and other parts and melts it down to produce concentrated fat and protein for use in various manufacturing processes and to produce meat and bone meal. MBM derived from animals deemed fit for human consumption is still used in pet food manufacture in the UK.