DISEASES OF PIGS

Two types of pigs are normally kept on farms, those that are being reared to sell as meat, and those kept for breeding. The majority of pigs are sold as meat, and they are kept during the period of rapid growth. These pigs are killed before they have stopped growing, and most of their troubles are, the illnesses associated with rearing. With mature breeding Pigs, the main troubles are infertility and the diseases associated with sows farrowing (giving birth) and rearing their litters. However, there are some diseases that affect pigs of all ages.

Many pigs illnesses can be prevented by good management and in particular the following points:

  • Good housing which shelters the pigs from rain and wind, but which allows them plenty of fresh air;
  • Keeping the pigs warm in winter and cool in summer. Pigs are not covered in hair the way that other animals are, and they suffer if they are too cold, too hot and if they have no shelter from the sun;
  • Feeding properly balanced rations to the different classes of pigs on the farm. Pigs must receive the correct amount of carbohydrate, protein, minerals and vitamins for their size and weight, and they must have access to clean water at all times; and
  • Keeping the pigs clean by cleaning out their pens every day and giving them fresh litter in the form of straw, stover or sawdust. Pigs are by nature clean animals and will defecate in the part of their pen away from the sleeping area. Regular daily cleaning will keep them free from lice and mange, and will reduce the flies in the piggery.

2.   MAJOR DISEASES THAT AFFECT ALL PIGS

ANTHRAX

This disease is occasionally seen in the pig. The infection is due either to eating the flesh of other animals affected with the disease or from the presence of spores in contaminated feed. The main forms of the disease are:

A diffuse oedematous swelling in the region of the throat with the animal having difficulty in breathing.

The sudden death of a pig with no other symptoms being observed. In this case the most noticeable feature is the failure of the blood to clot.

Never carry out a post mortem on an animal if you suspect it has died of anthrax because man can be infected with the disease very easily.

FOOT AND MOUTH DISEASE

This is capable of unlimited spread from one animal to another, and is regarded as the most contagious of all known diseases. It should be suspected whenever a number of pigs show lameness involving more than one leg. The disease must be notified to the nearest veterinary office.

SWINE FEVER

A highly infectious disease of pigs which is caused by a virus of which there are a number of different strains. The live virus has been found after 1 month in smoked and salted pork, after 2 months in the bones of smoked and salted pork and after 4 years in frozen pork, but the virus is killed by boiling and by disinfectants. In many countries, it is the law that all swill fed to pigs must be boiled.

The disease is spread from infected pigs or infected pig products, and it can be carried by birds, on clothes, or by cars and lorries, especially on the tyres. Once a pig has had the disease and has recovered, it is immune for life, and a passive immunity can be transferred from a sow to her piglets through the colostrum.

The incubation period is from 3 to 6 days but in some cases may be much longer. In acute cases animals are found dead, but in other cases the pigs will develop a high temperature with the fever spreading very rapidly through the herd. Affected animals appear listless and show a catarrhal discharge from the eyes and sometimes from the nose. As the disease develops, the animals suffer from severe diarrhoea and blotches appear on the skin; death occurs within one week.

Swine fever is difficult to diagnose because the symptoms are very similar to those of other diseases such as salmonellosis, and erysipelas. Once the disease has appeared in the animal no treatment is effective.

The disease can be controlled by a vaccination programme, with the careful selection of vaccine according to the strain of the virus, or by the use of a slaughter policy. This is used in the U.K. where all digs with the disease, together with those in contact with infected animals, are slaughtered and the carcasses burned on the farm. The farm is placed in quarantine and all the piggeries, vehicles, clothes of the stockmen etc. are thoroughly disinfected. Pig markets in the area are closed and the movement of pigs is forbidden. This policy can only be enforced by legislation.

AFRICAN SWINE FEVER

Is caused by a virus and affects domestic pigs, wild pigs and warthogs in Africa. It is spread by feeding un-boiled, contaminated swill to pigs, by direct contact with an infected domestic or wild pig, or by a tick bite. The symptoms are similar to those of swine fever, and infected animals usually die. There is no treatment or effective vaccine, and the disease must be prevented by always boiling swill before feeding it to pigs, and by preventing any contact between domestic pigs and wild pigs or wart hogs roaming in the bush. In the case of an outbreak, the best policy is to slaughter all pigs in the area, disinfect thoroughly, and allow a period of at least four months before re-stocking.

SWINE ERYSIPELAS

Is caused by a virus and affects mainly between 3 and 18 months old, although older pigs can be infected. Some digs are carriers of the disease and infect the soil in grazing areas through contaminated faeces. The bacteria are passed on to other pigs feeding in the same area, through food, through cuts and scratches on the pigs, or by means of flies. The disease can be acute or chronic. In the acute form, the animal has a high temperature, a discharge from the eyes, the skin on the abdomen becomes dark red and the animal usually dies. In the chronic form the animal develops stiff joints and characteristic diamond shaped, dark red patches on the skin.

The disease can be treated with injections of penicillin, but animals that recover should be sent for slaughter as they do not thrive. Control of the disease is difficult, the main precaution being to make sure that pigs brought into a pig unit are not carriers. Vaccinations are available, but their effectiveness is variable.

HEAT STROKE

Pigs are very susceptible to sunburn and heatstroke and should always have shade from direct sunlight. Heatstroke can be caused by direct sunlight or by bad ventilation and overcrowding in a pen. Affected pigs appear to be greatly distressed, have a very high temperature, as high as 44°C, and seem half paralysed. Death can occur very rapidly. Treatment is to move the pig to a cool, shaded place and douche it with cold water until the temperature falls to normal. Spraying the animal all over with a garden hosepipe is a good method of applying the cold water.

MANGE

All pigs and particularly breeding stock are susceptible to attack by mange mites which burrow into the skin and cause itching to the affected animal. Secondary infections can enter the raw patches on the skin caused by the animals rubbing and scratching. Treatment is by washing the animal with a proprietary remedy and all sows should be treated a week before they are due to farrow so that the mites do not infest the newly-born piglets.

WORMS

Pigs of all ages can suffer from infestations by roundworms (Nematodes), and tapeworms (Taenia Solium). All pigs should be dosed regularly with a proprietary worm remedy against roundworms, and sows should be washed with soap and water and dosed before being put into the farrowing quarters. This destroys any internal worms and any eggs that may be on the skin of the sow. All pigs should be given routine dosing against tapeworms. Eggs produced by tapeworms inside the animal hatch in the intestine, pass through the wall into the bloodstream and are carried around the body where they form cysts. If undercooked, infected meat is eaten by man, the cysts hatch out and become tapeworms inside the human host. This type of infected meat is called “measley” because of the small, round cysts.

FOOT CONDITIONS

These are common in breeding stock, the main causes being bruising or puncture wounds in the feet. The affected foot becomes swollen and a chronic abscess forms with infection entering the blood stream. Bad feet can be caused by:

  • A lack of bedding in the pen;
  • Roughly laid concrete in sow stalls, or badly constructed slats;
  • Broken or uneven surfaces at the exit and entry to pens; and
  • Continual soaking of the feet in the animals own excreta due to poor drainage.

Animals with bad feet should be walked through a foot bath once-a-week, the foot bath being filled with a 5% solution of copper sulphate.

3.   DISEASES OF SOWS

MASTITIS

Inflammation of the udder caused by bacteria such as staphylococci, streptococci, coliform, etc., does take place with sows, although it is far less common than mastitis in dairy cows. Infection usually occurs within 48 hours of farrowing, and signs are some enlargement, congestion, redness and pain in one or more of the teats and glands of the udder, often the piglets have to be taken off the sow and reared by bottle. Infection can be brought on by injuries to the udder, chills, damp floors, udder tension and high milking capacity. Treatment consists of applying antibiotics up the teat or by drenching the sow orally with sulphonamides.

MILK FEVER

This trouble occurs within a week of farrowing. The early signs are reduced appetite and some uneasiness, but the first to be noticed may be the collapse of the sow, inability to rise and loss of interest in the piglets. The udder becomes hard, the piglets cannot get milk and if left untreated the sow will die. As in the case of the cow, injecting a solution of calcium borogluconate effects a rapid recovery and the piglets can continue to suckle the sow.

FARROWING FEVER

This is a serious fever which begins within two or three days of normal farrowing. The sow becomes dull, loses her appetite, the udder becomes hard, the temperature rises to 41 – 42°C, and, untreated cases generally die. Treatment by sulpha drugs is effective but it must be immediate, as soon as the symptoms are noticed. It is good practice to take the temperature of sows every evening and morning for three days after farrowing, so that any rise in temperature is noticed at once and the sow can be treated. With early treatment, the piglets can be left on the mother, but if the sow loses her milk, the piglets must be hand fed, at least for a few days.

4.   DISEASES OF GROWING AND FATTENING PIGS

PIGLET ANAEMIA

This is a nutritional anaemia caused by a lack of iron, and it occurs in young pigs from about 3 weeks old. The anaemia is caused by a fall in the levels of haemoglobin, the red colouring matter in the blood which contains iron, and this causes the capacity of the blood to carry oxygen to fall. The skin under the eyelids and the gums of the piglets become a pale pink colour, they may develop diarrhoea, and many of the affected animals die. Piglets running with a sow on pasture, or with access to soil or turf, seldom develop anaemia. All piglets that are housed all the time should be given an injection of a proprietary preparation of soluble iron at three days old, and they may have to be injected again at three weeks old.

ENTERITIS

The symptoms of this condition are a high fever and severe diarrhoea in which there are blood clots. It can be caused by a number of factors, the main one being infection by bacteria of the Salmonella group. It is also a symptom in swine fever and swine erysipelas, it can be caused by eating some irritant material, and a temporary enteritis may follow a sudden change in feed. Enteritis caused by salmonella infection can occur in very young animals, but more often it happens in growing digs and adults. The fever and diarrhoea is often accompanied by pneumonia and mortality is high. Animals that recover frequently become carriers of the disease. Such carriers may bring the disease onto a farm, or it may be introduced in infected feed, particularly feed from animal sources. Treatment is by administering sulpha drugs or anti­biotics. Prevention can be helped by isolating animals coming onto the farm and by good husbandry and good hygiene, as stress can be a trigger for the disease.

BOWEL OEDEMA

This occurs in fattening pigs usually between 10 and 16 weeks old and often the best pigs in the group. The cause is unknown, but the disease often follows any abrupt change in feed. The course of the disease is very short, and some pigs may be found lying dead. Others go off their feed, develop swollen eye‑lids, and start to stagger, and within 36 hours become paralysed and die. Pigs in a group which show signs of the disease should be given a laxative, starved for 24 hours and fed lightly for a few days. Prevention is mainly by being very careful in making changes in the feed of pigs of all ages. Any change in rations should be done very gradually, over a period of a week.

PNEUMONIA

Outbreaks of respiratory diseases can occur in pigs that are housed intensively, and pneumonia is a common condition. Pigs housed in conditions of good ventilation and plenty of fresh air, are normally free of the disease, but intensively housed pigs, particularly in temperate climates, suffer from a condition called virus pneumonia. The symptoms are a cough and the pigs are generally unthrifty although they eat well, and the disease infects suckling pigs and weaners. Prevention is by isolating any new pigs that are brought onto the farm for a month, and any that are coughing should be slaughtered and a post mortem performed. Cases of pneumonia can be treated with one of the sulphonamide drugs or an antibiotic such as Tylan.

THE PRODUCER AND HIS VETERINARY SURGEON

Some or all of the conditions listed above occur on most pig units at some time or another. Their treatment demands that the farmer should avail himself of veterinary help.

Technical and professional veterinary staff are in a good position to deal with problems as and when they arise. Veterinarians engaged in research are constantly in touch with scientists in many countries in order to exchange knowledge and ideas relevant to producer problems.

A dead pig or material from it should be sent to the nearest veterinary office as soon as is practical after death. Where a litter or group of pigs are affected, it is preferable to send a pig before it dies. This makes positive diagnosis easier. Whether the animal submitted is alive or dead, it should be accompanied by a note identifying it, together with a short history of the circumstances and details of any treatment that it has received.

5.   GENERAL MANAGEMENT FACTORS

THE PERSONAL FACTOR

Management plays an essential part in pig production; indeed it is often said that management is the overriding factor leading to the profitability or otherwise of a pig enterprise. In practice, management falls into three categories.

  • The ability to manage the enterprise on a business basis. This involves proper handling of labour, financial affairs, the ability to decide on changes in systems employed, in buying of food and in marketing. Some of the economic aspect of management will be dealt with later.
  • The ability to keep up-to-date with technical matters affecting production and the willingness to adapt traditional practice in the light of new developments.
  • The ability to care for pigs that is stockmanship. This is the personal factor and is probably of greater importance than the other two. The good stockman is the one who is always on the watch for irregularities in the condition of each individual pig, who is scrupulously regular in his routine, who is firm but understanding with his pigs and who foresees trouble before it arrives. He must learn by observation and by his mistakes, but the best stockman, like the gardener with green fingers, is probably born and not bred.

HANDLING PIGS

Few animals are more responsive to training than pigs, and none respond better to quiet and kindness. Nevertheless, bad temper and viciousness in pigs are all too often seen. The results are poor growth in the animals concerned, crushing and savaging of piglets on the sow, and physical injury to the pig farmer in the case of boars. Nervousness and bad temper can originate early on, particularly when the pig is being caught or driven. In catching a suckling pig it is best to stalk from behind and lift it suddenly by one or both hind legs, it is then held around its shoulder. Bigger pigs should be caught by grabbing with both hands behind the shoulder and lifting off the ground. This is far better than catching by the tail and ear method commonly used, and the animal should then be held firmly against the body. When, driving pigs, it must be remembered firstly that the pig cannot be led by its head like a horse, and secondly that the pig’s instinct is to head for a gap and go bald-headed through it. Consequently, the proper way to drive a pig is to make use of this instinct.

Prevent him seeing a gap in any direction but that in which he is to go, and he will go in that direction. As much use as possible should be made of walls and solid hurdles or boards. Permanent buildings should be designed so that all pig movements should be between the walls of narrow passages, and a ramp built on these principles is a boon when loading pigs onto transport to the slaughterhouse.

RESTRAINING PIGS

It is sometimes necessary to restrain large pigs such as sows or boars for the purpose of treatment. Quiet sows can sometimes be restrained by confining her with a hurdle at the corner of a pen, but this will not keep most animals still, especially boars. The best method is to restrain a pig by a rope around the snout as follows:

Make a slip knot in a 2m length of rope and allow a large enough noose to pass around the pig’s mouth, encircling the snout close up against the juncture of the upper and lower jaws, and when in place, draw tight. If necessary, twist the surplus rope round a railing or pole, but normally a man holding firmly at about 35 degrees to the horizontal will be able to hold the pig, which will sway pull against the pressure and stand firm for any treatment. For quick release, do not pull the rope right through when completing the knot, but leave it in a loop. By pulling the loose end the knot will fall apart.

TRANSPORTING PIGS

The transportation of pigs to a slaughterhouse imposes stress on the animals. The pigs are in new surroundings, are mixed with strange pigs from other pens, and jolted by the stopping and starting during the journey. Obviously, the stress is worse in hot weather and as a result, a proportion of pigs are dead on arrival at the slaughterhouse. Such deaths can be reduced to a minimum if some fundamental rules are observed:

Before loading, do not feed for at least 10 hours beforehand. During loading, use a properly designed loading pen with solid walls and a ramp and do not put animals of different mass, for example, porkers and baconers, together.

The truck must provide a cover overhead and subdivisions should be used so that not more than 10 animals are together. The floor should be rendered non-slippery with wooden slats, and adequate bedding provided. The sides and the door should be devoid of large gaps and high enough to prevent the pigs trying to jump out.

While travelling do not stop en route to the slaughterhouse and avoid travelling during the heat of the day. If there is a delay at the slaughterhouse, an attendant should be with the pigs to minimise fighting and, if possible, spray the pigs with cold water.

HYGIENE

Cleanliness of the housing, surroundings and pigs undoubtedly helps to reduce disease incidence. It also has a beneficial psychological effect on the staff, by helping to improve the working environment. A programme of cleaning and disinfection should be worked out appropriate to the farm and the management system. All buildings and rooms within the pig flow should be periodically emptied. This is especially important in a large farrowing house, where a week’s rest in between batches of farrowing is recommended. With cages and finishing pens, four to five days of rest seems satisfactory.

There are several aids to cleaning such as pressure washers and steam generators. In practice, the system of scrubbing out a pen immediately when it is empty, followed by swilling with a disinfectant solution, and leaving the pen to stand dry for a few days, will give satisfactory results.

VICES

Tail biting and cannibalism occur in many units and yet little is known of the causes. There is no doubt; however, that environment is the major factor involved. These vices rarely occur in outdoor or extensive systems, but are more likely to occur under the following conditions:

  • Over-stocking of dens
  • Lack of bedding
  • Floor feeding
  • Poor ventilation, especially under hot and humid conditions

Vices are most commonly seen in intensive systems that use no bedding. If an outbreak should occur Stockholm tar should be applied to all tails that have been bitten, and a calf elastrator ring applied about 4cm from the root so that the tail will drop off in a few days. A sprinkling of bedding and a chain hanging from the roof is often enough to prevent further incidence, but if it persists, then, all pigs in the pen should be docked by elastration. If bedding is not to be resorted to, then all pigs should be tail docked at three days of age.

The vices described above should not be confused with fighting, which always occurs when groups of pigs are mixed. The fights result from the instinct of pigs to establish a pecking order, and once this has been established, usually within six hours, no more fighting occurs. It is difficult if not impossible to prevent this fighting when strange pigs are mixed. It can be minimised but not eliminated by having an attendant present and by ad lib feeding for a few hours.

The rule, however, is to avoid mixing pigs older than nine to 10 weeks of age, because fighting among bigger pigs causes damage and sometimes deaths.