The pig belongs to the non-ruminant section of the Artiodactyla or even-toed ungulates. All domesticated pigs are descended from two closely related species, Sus scrofa, the wild pig of Europe and North Africa, and Sus vittatus from Asia, mainly China and Siam. The European pig was thin with a long, pointed face, and of the modern breeds the Tamworth is most closely related to this type. The Asian pig had short legs, a wide dished face and the ability to fatten rapidly, and the influence of this type can be seen in the Berkshire and Middle White breeds. Most of the modern breeds have evolved from these two wild pig types and the fixing and improvement of breeds has taken place over the past 100 years.
Pigs are kept only for the production of meat, and as the meat can be used in different ways, there are two body types for which pigs have been bred, the pork type and the bacon type. Pork pigs are kept for the production of fresh meat, while bacon pigs produce cured meat, bacon and hams. Of all the farm animals, the pig has the greatest capacity to accumulate body fat early in life, and early maturation has been obtained to a far higher degree than in sheep and cattle. As people do not like too much fatty meat on a joint or rasher of bacon, the farmer must try to control the growth of the pig so that the animal is not too fat at slaughter. Pork pigs are slaughtered at 55 – 70kg live mass, and bacon pigs at 90kg live mass. The pork pig must reach the right stage of development and proportion of fat and lean meat at 55kg, while the bacon pig must reach that same stage and proportion of fat and lean meat at 90kg, or roughly twice the weight of the pork pig. The difference between pork and bacon types of pig is one of early maturity, and this is produced most economically by feeding the animal to its appetite. Until recently, this was achieved by having pork breeds and bacon breeds of pigs, the pork breeds being early maturing, and the bacon breeds being later maturing. Pigs of a pork breed kept on to bacon weight would become too fat, while those of a bacon breed slaughtered at pork weight, would be too immature and unfinished. The difference between these two types can be seen in the diagram below:
Figure 1: shows the difference between pork weight and bacon weight
In modern pig husbandry this difference between pork and bacon breeds, is less important. This is due to better breeding, selection and above all, more scientific feeding. Pig rations used today are so well balanced, that the growth and fat formation of the animal can be controlled by the farmer, to produce exactly the type of pig which he requires. In fact, most pigs today are fed far better than many humans, and the hybrid pig will produce good quality pork or bacon depending on feeding and age at slaughter.
There are many different breeds of pigs in the world and those covered in this lecture are the ones that are common in Southern Africa.
Originated in Yorkshire in the United Kingdom (U.K.) and is the largest pure breed. Mature pigs can reach a weight of 500kg which is the same weight as a mature cow. The main characteristics are a white skin, upright or ‘prick’ ears, and a long body. A white skin and length of carcass are desirable qualities for bacon production. The sows are good milkers and produce large litters, but they are not very docile and can become excited and harm their little pigs. The pigs are rather slow maturing and have always been a bacon type of breed, although there are strains of the breed that are suitable for pork production today.
Figure 2: Large White Pig
The Landrace was bred in Denmark for bacon production, using the local pig and imported Large White blood. They are a modern breed and early Landrace pigs were exported all over Europe until the Danes prohibited all further exports, to protect their bacon markets. A few boars and gilts were imported into U.K. from Sweden in 1949 and 1953, and the Landrace herd book was formed in the U.K. in 1953; it is now the second largest breed in that country. The pigs were selected for bacon production and are very long, with white skins and lop ears. The sows produce good litters and are docile and good mothers.
Figure 2: A Landrace Pig
Is a breed very similar to the Landrace being white in colour and with good bacon characteristics.
Figure 3: A Welsh Pig
These three pure breeds have been imported into Southern Africa over the past 50 years, and are found on the farms of pedigree breeders. They are used to produce boars that are bought by commercial pig producers and used for crossing. In addition to the three breeds discussed, there are a number of pure breeds that are used as foundation stock for the production of the hybrid pigs that are rapidly becoming the main stock kept by commercial pig producers.
Is an amalgamation of the Essex and Wessex breeds. They are black pigs with a white band over the shoulders. The sows make very good mothers being good milkers with a quiet temperament. The pigs are efficient grazers and can make good use of bulky fodders, and they are hardy. This is a pork breed being too short for bacon production, but a common practice is to cross a large white boar with a Saddleback sow to produce a crossbreed, or hybrid, which is a good bacon pig.
Figure 4: A Saddleback Pig
Is only slightly smaller than the Large White and is black all over. The sows are good mothers and very docile. The breed is used for crossing to produce hybrids.
Figure 5: A Large Black Pig
Is the nearest living relative of the wild pigs that used to roam the forests in the U.K. It is a golden red colour with a long slim head and snout.
The pigs are hardy, good foragers and produce a lean, high quality bacon carcass, but they mature very slowly.
Figure 6: A Tamworth Pig
Is a Belgium breed with a carcass containing a high content of lean meat, large eye muscles, good hams and a high killing out percentage. The meat quality is poor, and they have a slow growth rate, short body length and poor litters.
Is an American meat hog with a black skin. It has the same advantages and disadvantages as the Pietrain.
Is an American meat breed with good lean meat and a very good food conversion, but poor litter numbers.
Is the most popular American breed with good litters, food conversion and very good daily live-weight gains. It tends to produce over fat pigs.
Is a new Canadian breed bred for crossing with other breeds. It has the same characteristics as the Duroc.
Indigenous pigs found in Central Africa were probably introduced by the Portuguese during the 19th century. They are of the black Windsnyer type with long noses and razor backs. Mature males reach a weight of 110kg and females about 60kg. They are kept mainly in the rural areas and are not penned, but they serve as scavengers around the kraals. They survive on a varied diet of maize, brewing by-products and household scraps. They are hardy and better equipped to deal with a variety of low grade foods. Indigenous pigs grow more slowly and produce much fatter carcasses than the imported breeds, so that they cannot be kept for sale to the normal markets for pig meat. Their main use is to be kept for home consumption in the more remote areas of the country.
The term hybrid was first used in agriculture 50 years ago to denote a cross between two inbred lines of maize, with the first cross (F1 generation) showing a large increase in yield. The term was then used by the poultry industry in producing hybrid hens. These are produced by crossing several inbred lines which have been selected carefully for various traits; egg numbers, egg size, disease resistance, food consumption etc.
Hybrids have been developed for the pig industry, and most commercial pig stocks are hybrids of one type or another. Due to the slowness of the breeding process compared to plant and poultry breeding, a pig hybrid means a cross between two or more strains or breeds, and no prior inbreeding is implied. The reasons and the methods used for the breeding of hybrid pigs are given in the next lecture.
The following terms are commonly used in pig husbandry.
Boar – A male pig of any age
Sow – A mature female pig
Gilt – A young female pig up to the time of weaning her first litter
Suckler – A young pig suckling its dam
Weaning – The time when young pigs are removed from their dams
Weaner – A young pig that has been weaned and normally 6 – 8 weeks old
Farrowing – Giving birth to a litter
Litter – The batch of little pigs produced by a sow at farrowing
Porker – A fattening pig up to 74kg live-mass
Baconer – A fattening pig between 75 and 94kg live-mass
Manufacturing pig – Any boar, sow or overweight pig sent for slaughter
Figure 7: Piglets Eating Feed