The cause of intestinal torsion in pigs is unknown; how the disease actually progresses has not been proven. However, this disease has been associated with whey feeding and grain-based diets.

Most losses occur in pigs between two and six months of age, occasionally older pigs are affected. Most affected pigs are found dead with pale skin and abdominal distension (bloat). Other clinical signs include:

• bloating a short time after feeding
• severe abdominal pain with pigs screaming
• difficulty breathing
• dog-sitting.

Pigs lie down and get up repeatedly due to abdominal discomfort, collapse, and finally die. The time from the onset of clinical signs to death ranges from one to 12 hours.

Some piggeries have occasional (sporadic) losses due to this disease, in others it is a year-round problem.

It is believed that gas production in the intestines (bloat) precedes torsion or twisting of the large intestine. Once the twist occurs, the intestine rapidly becomes oxygen-deficient and the pig dies suddenly from shock. It is possible that some pigs die from bloating without the intestine twisting. It has not been proven but circumstantial evidence suggests the problem is related to a low-fibre, high-energy diet. One theory is that undigested carbohydrate (usually grain such as sorghum) is fermented in the large intestine and the subsequent gas production causes bloat. The light gas-filled large intestine, which is normally below and forward of the small intestine, simply flips through a 180° twist.

After death, the carcase is very pale, the abdomen is distended and the mucous membranes of the mouth, eye, vulva and anus are dark red. The carcase of a pig that has died from intestinal torsion often decomposes faster than normal. If the pig is laid out on its right side, and the left abdominal wall is carefully removed, the small intestine will be found in an abnormal position forward and below the large intestine which is distended with gas.

The small intestine is heavy and contains blood (red gut, bloody gut). By carefully holding down the gas-filled large intestine a twist in the root of the mesentery (the tissue that supports the small intestine) can be found immediately below the left kidney. All of the pig's intestines are attached to the abdominal wall at this point except for the first part of the small intestine (duodenum) and the last 30 cm of the large intestine and rectum.

Therefore, the duodenum and last part of the large intestine and rectum are free of blood. The torsion blocks the thin-walled veins draining blood from the intestine, while the thick-walled arteries are not blocked and continue to supply blood to the intestines before the pig dies. This results in the intestines being dark red and congested with blood after the pig dies (red gut, bloody gut).

This disease is diagnosed by the clinical signs and the detection of the intestinal torsion at post-mortem.

No known treatment or control is available for this disease. A similar disease to this has been described that was due to vitamin E deficiency, however intestinal torsion was not seen; only bloat, bloody gut and sudden death. Try to minimise the amount of whole grain in pig feed. Further research is required to determine the factors that predispose to intestinal torsion.