The aim of the pig industry in all cases is to produce a lean carcass. Most of the fat in a pig is found subcutaneously (under the skin) and this has led to the development of payment schemes for carcasses based on subcutaneous fat measurements (eg 12 probe means that the pig has 12mm of subcutaneous back fat), weight and in the case of bacon pigs, a minimum length.
When pigs are killed for bacon:
The head including brain, trotters, tail, testicles, offal etc are processed into pre-packed meat i.e. American style ham, sandwich meats, sausage and convenience products (it also goes into lamb, beef and turkey processed foods).
The forelegs, neck and back legs may be used for roast joints.
The remaining carcass is tubular in shape and goes to a bacon processing plant where blades strip the meat off.
Bones and scraps go for pet food or MRM (mechanically recovered meat used in processed foods).
Pork pigs are 14 probe (14mm back fat) whereas bacon pigs are 10-12 probe. With pork pigs the head, feet, tail, offals go for processing to pre-packed meat; the rest is chopped and sent to wholesalers 'fresh'.
There are three main breeds of pig in Britain: Large White, Landrace and Welsh. Breed differences are not obvious other than the fact that the Whites ears are pricked up whereas the other two point forward. The Large White is usually viewed as being more prolific and faster growing with a 'better quality meat'.
Several other UK breeds eg British Saddleback, Tamworth, Gloucester Old Spot and Large Black are also bred to a much smaller extent, often in outdoor free range systems.
About 75 % of UK pigs have been cross bred, because these 'perform better'. Animal production academic, Lean states:
"Traditionally, commercial producers crossed only two breeds of pig, eg the Large White and Landrace, to produce high quality piglets which showed the beneficial effect of hybrid vigour. Pig breeding companies have improved in this technique by selecting high performance lines from various pure breeds and combining them.... The resources of a large breeding company allow considerable control of all aspects of selection and guarantee the producer high performance animals at all times." (1)
Some companies specialise in breeding pigs and they are considered specialists in the field. They supply genetically 'improved' pigs to multipliers and commercial producers and so new genetic lines percolate the whole industry. The biggest company in Europe is PIC (Pig Improvement Company.)
These specialist breeders now supply a considerable proportion of gilts to the commercial producers.