Piglet scours is estimated to cost the Australian pig industry more than $7 million each year. The incidence and type of scours, health costs and recovery rate determine the extent of this loss in individual piggeries.
Scours (diarrhoea) is the excretion of faeces containing excess fluid. Depending on the cause of the scours, there may also be blood, undigested food, mucus and pieces of membrane from the intestinal lining.
The hard-working digestive system is responsible for the intake and digestion of food, absorption of nutrients and the excretion of waste material. Pathogenic strains of certain bacteria (those capable of causing disease) and non-pathogenic bacteria, are normal inhabitants of specific sections of the gut. Some organisms assist in the breakdown of feed and the production of nutrients. Changes to the gastrointestinal environment may upset the balance between gut and bacteria. In turn, the secretion of fluids and electrolytes into the stomach and gut, the rate of passage of food through the system and the ability to digest and resorb nutrients, water and electrolytes are also affected. An upset in the digestive system is frequently observed as scours.
Water and electrolytes (salts) are essential for the pig's body to operate in a state of physiological balance. Insufficient quantities prevent the normal function of body processes.
Poor nutrient absorption
When scouring reduces the absorption of nutrients from the gut, the pig has to call on its own body reserves for maintenance. In very young pigs, energy stores are easily exhausted and they may die or lapse into a coma. In chronic cases, body condition loss is evident and some animals may be so distressed they do not eat.
Rapidly multiplying bacteria in the gut may result in the bacteria spreading, or toxins being released into the bloodstream (septicaemia and toxaemia). Sudden death without signs of scouring may follow.
Predisposes to other diseases
When the body is in a poor state as a result of scours, other organisms may take advantage. In some piggeries pneumonia may occur as a secondary complication to scours in young pigs.
After a severe bout of scours the digestive track can take some time to repair. Affected pigs may become 'poor doers' and scour periodically for some time afterwards.
There are different types of scours that may affect pigs:
Dietary/nutritional scours can be caused by a change in the quality, texture and perhaps quantity of feed; toxic elements in either the feed or water (for example, arsenic in excess or high levels of specific salts in the water); insufficient iron after birth (complications with intestinal infections).
Bacterial scours (Escherichia coli (E. coli)) may be caused by salmonellosis, swine dysentery or campylobacter infection (adenomatosis, necrotic ileitis, proliferative haemorrhagic enteropathy).
Viral scours may be caused by swine fever, transmissible gastroenteritis (not present in Australia), rotavirus and reovirus are thought to be involved in some scours.
Parasitic scours may be caused by a heavy burden of internal parasites such as gastrointestinal worms or coccidiosis.
Any of these factors may start a scour problem but certain strains of E. coli are the most frequent cause of scours. E. coli organisms normally live in the animal's gut and pass out in the dung of grower and adult pigs.
|Baby pig scours||
Scours in suckling pigs generally occurs within a few days of birth (neonatal scours, neonatal colibacillosis) or at 2 to 3 weeks of age. A litter may seem healthy at birth and enough milk is supplied by the sow, but between 12 and 96 hours of age the litter suddenly becomes affected. One or two piglets may die while others show varying degrees of diarrhoea and listlessness. The scour is usually light in colour, very liquid and foul-smelling. Septicaemia, toxaemia, rapid dehydration and loss of vital electrolytes cause high mortality unless promptly treated.
For up to 36 hours, piglets can absorb the antibodies contained in colostrum. Maximum antibody protection is obtained if absorption occurs within the first few hours of life. Colostrum is rich in the sow's antibodies, which have developed during her exposure to the piggery's resident organisms.
|Predisposing factors for baby pigs||
The piglets absorb less than normal amounts of colostrum and antibodies due to:
Piglets may have inadequate protection by the colostrum because:
In unhygienic farrowing pens the piglet's defence mechanism is challenged by too many bacteria.
In a cold or wet environment the piglet's natural defences may be weakened.
|Pre-weaning scours at 2-3 weeks||
The second peak time for scours to occur is at 2-3 weeks of age and is often referred to as 'milk scours'. Healthy pigs begin to scour and although severe setbacks may occur, few deaths result.
At this age E. coli are well established in the gut, but certain factors allow the pathogenic strains to multiply rapidly.
|Predisposing factors for 2 to 3-week-old piglets||
Passive immunity acquired from colostrum falls after 1 week and by 2 weeks is very low. Low levels of antibodies, however, continue to be secreted in the milk. These are not absorbed, but protect the gut lining. Immunity developed by the piglet (active immunity) is immature at this age.
By 1 week of age, piglets may eat small amounts of food. The gut chemicals (acids, enzymes) and bacteria present at this age are more efficient at digesting milk than grains or protein sources other than milk proteins. Even up to the age of 4 or 5 weeks the digestive system is unable to handle large amounts of dry food. Undigested food in the lower gut allows potentially pathogenic strains of E. coli to multiply and invade other areas of the gut. Overproduction of milk by the sow may overload the piglets' intestines, predisposing to E. coli scours.
The build-up of bacteria over time in the farrowing pen can overwhelm the young pig's defence system.
The presence of other diseases may predispose young pigs to scours e.g. pneumonia, iron deficiency anaemia.
|Preventing sucker scours||
The bacterial population in farrowing pens is reduced by cleaning, disinfecting and spelling after each litter is weaned (the all-in all-out system is ideal).
Immunity is encouraged by:
Stress can be reduced by:
|Acute and sub-acute weaner scours||
Scouring is common, particularly in pigs weaned between 14 and 28 days of age. Pathogenic strains of E. coli are present in the gut at weaning, and conditions at the time may favour their multiplication. A variety of symptoms may be seen 4 to 7 days after weaning:
In the 3- to 4-week-old weaner pig, the active immune system is immature and the passive immunity acquired from colostrum is by now very low. Contact with new strains of organisms may occur at weaning.
Sows' milk is easily digested by young animals and weaning on to solid food is an abrupt change to the piglet's system. Gut enzymes and bacteria are not fully prepared to handle a change at this age. Although solid food is initially eaten in small quantities, hunger compels the animals to eat more and more, overloading their stomach and gut. Bacteria can multiply in undigested food and pathogenic strains take advantage of the situation and predominate.
Weaning stress in piglets is triggered by being:
Chronic, post-weaning coliform scours commonly occurs in piglets housed in contaminated, cold pens. Scours result from continuous overwhelming doses of E. coli and other bacteria.
The following attempts may be made to reduce potentially dangerous changes happening in the gut at weaning time: