Intensive farming methods have lead to increased disease problems; these are particularly prevalent amongst piglets. Viral pneumonia, meningitis, swine vesicular disease, blue-ear disease, scours, infertility and diarrhoea are just some of the diseases that can affect pigs.
Porcine Reproductive and Respiratory Syndrome (PRRS) / Blue-ear Disease
This is caused by a virus and symptoms in sows include fever, abortion, premature birth, coughing and respiratory signs. Foot and Mouth This is an infectious disease caused by a virus (of which there are 7 types). The virus affects cloven-hoofed animals such as cattle, sheep, pigs, goats and deer. The disease is not normally fatal to adult animals but it does cause debilitation and loss of productivity for farmers (such as lameness). The virus causes a fever and the development of blisters, mostly in the mouth and on the feet. Animals contract the disease by either direct contact with an infected animal or contact with foodstuffs, etc. which have become contaminated by an infected animal. The UK last experienced the disease in 2001, with 2,030 confirmed cases of foot and mouth spread across the country. 0.4million pigs were culled as a result of this outbreak (1).
Classic Swine Fever (CSF)
This is a contagious disease caused by a virus. It was eradicated from Great Britain in 1996, since which there have been several outbreaks of the disease which were controlled by the slaughter of many pigs. The initial source of CSF virus appears to be from pigs eating infected pork or pork products derived from imports. Infected pigs may show little evidence of disease or can develop a fever and lose their appetite. Other possible signs include discolouration of the skin, diarrhoea, constipation, coughing and nervous signs.
This disease can affect other species (not horses/humans), but it does mainly affect pigs. It is caused by a virus and was last recorded in Great Britain in 1989, although much more recently in Northern Ireland. The symptoms shown depend on the age of the pig and include both nervous and respiratory system problems with abortions and stillbirths in pregnant females. The number of fatalities is higher in younger pigs.
Modern pigs have been selectively bred for fast growth which can lead to lameness and other leg problems, the pigs being unable to support their own rapid weight gain. Around 15% of pigs are estimated as suffering from lameness though this may be considerably higher in some herds. Mothering pigs have the added problem of coping with rapidly growing suckling piglets. This can cause the sow a loss of bodyweight and loss of bone tissue leading to hip or spinal bone fractures.
Porcine Stress Syndrome (PSS)
Other breeding has involved developing breeds that are less prone to stress. Porcine stress syndrome is attributed to a specific gene, called the halothane gene. PSS leads to pale, watery meat of low quality, poor appearance and shortened shelf life. Selective breeding has produced strains in which the halothane gene has been eliminated. These stress-free pigs have lower mortality (especially during transport to slaughter when many deaths can occur) and are said to produce higher quality meat.
Genetic Engineering/Breeding Pig breeders have developed a sow with extra teats and larger litters by crossing a traditional British breed with the Chinese Meishan pig. Meishan sows have up to 18 teats and average 16 piglets per litter compared with 12 teats and 11 piglets for British breeds. They are very high in fat so not suited to the meat industry's requirements. Cross breeding has produced a hybrid, called the Manor Meishan, with the advantages of the Meishan but with lean meat content. The pig industry hopes this new breed will produce 30-40 piglets/year. Genetic engineering techniques are likely to become important for producing even more profitable pigs in the future. Transgenic pigs have been created which produce extra growth hormone so grow faster on less feed and produce very lean meat. Previous attempts have yielded pigs that were impotent, arthritic and barely able to stand. Pigs have also been produced with meat containing high levels of omega-3 fatty acids.
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