Dehydration/electrolyte loss

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.

Septicaemia/toxaemia

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.

Intestinal damage

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
• bacterial
• viral
• parasitic.

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.

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.

The piglets absorb less than normal amounts of colostrum and antibodies due to:

• lack of milk (sow has agalactia, death of sow)
• too weak to suck (runts, stores of energy exhausted, prolonged birth process)
• insufficient viable teats and sow has started to secrete colostrum several days before, so there are low antibody levels at farrowing.

Piglets may have inadequate protection by the colostrum because:

• sows, particularly the younger ones, were not adequately exposed to all strains of bacteria in the piggery
• introduced animals lack antibodies to all strains of bacteria in the piggery
• new strains of E. coli were introduced by outside pigs.

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.

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.

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.

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:

• controlling agalactia in the herd
• ensuring that piglets receive colostrum early in life, fostering them on another sow if necessary
• mixing gilts with older sows or feeding them sow dung before mating and during late gestation to stimulate immunity to resident bacteria
• restricting the number of animal introductions from outside piggeries
• vaccinating sows with E. coli vaccine before farrowing.

Stress can be reduced by:

• providing a warm, dry creep area
• reducing the sows feed intake temporarily by 30% if scouring at 2 to 3 weeks occurs; the piglets get less milk and there is less burden on their gut.

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:

• sudden death
• staggering
• animals on their sides with limbs paddling
• varying degrees of scouring
• reduced growth rate
• rough-looking appearance.

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:

• separated from their mother and placed in new surroundings
• mixed with strangers
• separated from a heat source
• exposed to a new strain of E. coli chronic scours.

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:

• Offer the weaner diet to sucking pigs fresh each day from an early age (5 to 7 days). Eating solid food early in life can predispose the piglet to nutritional scours but the diet change will be less severe at weaning. Changes in gut bacteria and secretion of enzymes more suited for digestion of weaner type diets are encouraged when this is done.
• Mix piglets of similar size at weaning wherever possible.
• Weaning into large groups should be avoided (10 to 15 pigs is ideal in a weaner pen but may not be practical in some sheds).
• Weaning into a clean, dry, warm environment is essential; ideally into pens which remain clean and dry.
• Feed intake should be restricted, particularly around the 3 to 5-day mark when weaners will tend to gorge themselves. Small amounts of food offered a number of times daily greatly assists in reducing the incidence of scours. Where restricted feeding is practised, adequate trough space is essential (up to 25 kg liveweight, 150 mm per pig is sufficient).
• Simple weaner diets rather than high-nutrient dense-type diets and using animal rather than vegetable protein sources, have been found to be beneficial in some piggeries.
• Where scouring is a problem, weaning at an older age is recommended (30 to 35 days rather than 21 to 25 days).
• Fresh water needs to be available at all times. Weaner pens should have watering devices similar to those in the farrowing pen (so that piglets know how to use them).

• Use antidiarrhoeal agents such as bentonite or kaolin clay to protect the gut wall.
• Replace electrolytes and fluids lost through scouring by adding electrolytes to drinking water.
• Reduce the population of bacteria in the gut with antibacterial agents (avoid drug abuse as resistance will develop).
• To reduce the severity of scours at two to three weeks of age, temporarily restrict the sows feed intake by 30%.
• Restricting feed for 12 hours may help scouring weaners.
• If pens are grossly contaminated with bacteria move the pigs to a cleaner pen.
• Provide a heat source, as warmth is beneficial.

• Pathogenic strains of E. coli are the most common cause of scours in sucking and weaned pigs.
• Pathogenic and non-pathogenic strains of the bacteria are part of the piggery environment.
• When conditions are suitable for the pathogenic strains to predominate, outbreaks of disease occur.
• Aim at a standard of hygiene that will reduce the challenge to pigs by pathogenic strains of bacteria.
• Ensure that piglets get colostrum within the first few hours of life.
• Discourage certain strains of bacteria from multiplying in the gut.
• Keep the environment warm and dry. Aim at prevention rather than cure.