Background and history

This is a widespread condition occurring in good growing pigs from 8 to 20 weeks of age. The onset is sudden. The size of the prolapse varies from 10 to 80mm and if small it will often revert to the rectum spontaneously. In most cases however the prolapse remains to the exterior and is often cannibalised by other pigs in the pen as evident by blood on the noses of the offending pigs and on the flanks of others. The fundamental cause is an increase in abdominal pressure which forces the rectum to the exterior.

Clinical signs

At the onset the red coloured mucosa of the rectum protrudes from the anal sphincter and then may return on its own. After a short period however it remains to the exterior and becomes swollen and filled with fluid. It is prone to damage and haemorrhage and where pigs are loose housed cannibalism often results with evidence of blood on the skin.

Weaners and growers

• The size of the prolapse varies from 10 to 80mm and if small it will often revert into the rectum spontaneously.
• In most cases however the prolapse remains out becomes swollen and filled with fluid.
• It is also prone to damage with haemorrhage.
• Cannibalism often results by other pigs in the pen as shown by blood on the noses of the offending pigs and on the flanks of others.
• Blown up abdomen seen in pigs 2 - 4 weeks after prolapse (rectal stricture).
• Pale pigs due to haemorrhage.
• Constipation.
• Sometimes death.

Piglets

• Rare.

Sows

• At the onset, the red coloured mucosa of the rectum protrudes from the anal sphincter.
• May return on its own or remain to the exterior, become swollen and filled with fluid.
• It is prone to damage, haemorrhage and cannibalism.
• Pale pigs due to haemorrhage.
• Blood in faeces.

Diagnosis

This is based on the clinical signs

Causes

The exact mechanisms are not understood but the following should be considered as contributory factors.

• Prolapses which occur after oestrus in the sow may be related to sex hormone levels.
• Penetration of the rectum at mating may result in prolapse 24-48 hours later.
• Stalls or tethers with an excessive slope of the floor towards the back.
• Sow stalls or farrowing crates with the back retaining gate consisting of parallel bars seem to predispose. If the sow can rest with the tail over the back gait, pressure is placed on the anus. This causes a partial relaxation of the sphincter, poor circulation and swelling. The sow strains and prolapses.
• Genetic factors do not appear to have a part to play in this condition.
• Trauma
• Tail docking - docking tails too short can damage the nerve supply to the anal ring leading to a relaxation of the anal sphincter.
• The fundamental cause is an increase in abdominal pressure which forces the rectum to the exterior and a swelling of the mucous lining and then straining.
• The Pig Site's partners Biomin have written an excellent account of the effect of Mycotoxins in swine which include prolapse of the rectum.

The following may be considered as causal or contributory particularly in growers.

• Diarrhoea - excessive straining.
• Respiratory disease - excessive coughing increasing abdominal pressure.
• Colitis - abnormal fermentation occurs in the large bowel with the production of excessive gas increasing abdominal pressure.
• In cold weather the incidence of rectal prolapses increases. This is associated with low house temperatures and the tendency of pigs to huddle together, thus increasing abdominal pressure.
• Wet conditions and slippery floors, particularly those with no bedding, increase abdominal pressure.
• If stocking densities reach the level whereby pigs cannot lay out on their sides across the pen the incidence may increase. It is often related to specific houses on the farm.

Nutrition

• Ad lib feeding - Feeding pigs to appetite results in continual heavy gut fill and indigestion. There is then a tendency for abnormal fermentation in the large bowel because undigested components of the feed arrive in greater amounts.
• High density diets and in particular lysine levels increase growth rates and outbreaks may often subside either by a change to restricted feeding or using a lower energy/lysine diet.
• Water shortage - this can lead to constipation.
• Diets high in starch may predispose to prolapse - try adding 2-4 percent grass meal to the diet.
• The presence of mycotoxins in feed - if there is a problem make sure that the bins have been well cleaned out. Examine the cereal sources.
• Change of diet - by studying the timing of the problem it is sometimes possible to identify rectal prolapses not only with a change of diet but also a change of housing.
• Field evidence does not identify breed as a causal factor.
• Increases in rectal prolapses have been reported in association with the use of tylosin but the evidence for this is unclear.
• Trauma
• Tail docking - docking tails too short can damage the nerve supply to the anal ring leading to a relaxation of the anal sphincter.

Prevention

Identify those factors on your farm from the above list and make appropriate changes.

Consider collecting the following information about each prolapse to see if common factors emerge:

• Age of pig.
• Comments observations.
• Days in the house.
• Diet fed.
• House and pen.
• Number of pigs per pen
• Number of rectal strictures.
• Number of prolapses sutured.
• Outcome.
• State of prolapse.
• Tail biting.
• Weight of the pig.

Treatment

• Rectal prolapses must be recognised early and the pig removed from the pen.
• Replace the prolapse and retain it by a purse string or mattress suture. Return the pig to the pen. The technique for carrying this out is described in chapter 15. If the prolapse has been badly torn still replace it, and consider moving the pig to a hospital pen and treat with a long-acting antibiotic injection. In a proportion of pigs the damaged tissues become scarred with constriction leading to rectal strictures. The incidence of this is reduced by replacing the prolapse and suturing.
• In some cases the prolapse will be completely bitten off by other pigs. Here the pig should be left in the pen as most cases will progress to slaughter although a few will develop with rectal strictures.