Age affected: Growers / finishers, gilts, sows.
Causes: Overfeeding; irregular feeding.
Effects: Distended abdomen, sudden death.
Torsion of the stomach is a well-defined condition which usually occurs in pregnant sows on once daily or less frequent feeding regimes where the animals are hungry and where a large quantity is fed at once. The excitement produced by the progress of the feeding process often results in clockwise twisting of the stomach sometimes together with the spleen. Once the stomach has twisted, the contents ferment, trapped gas causes the organ to swell and the sow dies rapidly from raised intra-abdominal pressure or shock.
Death can also result from rupture of the spleen and loss of blood into the abdominal cavity. Torsion of the intestines is most common in growing and finishing pigs and may be spontaneous or occur in association with enteritis. There are a number of predisposing factors.
In sows, ossification of the root of the mesentery may give rise to sharp flakes of bone which tear the mesentery and allow torsion to take place, in younger pigs, the adhesions of Glässer’s Disease may restrict intestinal movement and in finishers on rations containing whey or other carbohydrate-rich liquid, fermentable carbohydrate may reach the caecum, ferment and cause torsion of the whole large intestinal mass around its root.
The condition as such is not transmissible. Where torsion results from management factors,such as feeding regimes for sows in advanced pregnancy, the condition may recur when these factors persist. In the case of torsions associated with the consequences of infectious disease, such as the fibrosis following Glässer’s Disease, transmission occurs by the routes occurring in the disease, and torsion may result.
In most cases the affected animals are found dead. In sows with gastric torsion the predisposing excitement is associated with feeding and the early signs are more often seen. The sow is dull, uncomfortable, inappetent and the abdomen swells markedly prior to death. There may be respiratory distress and cyanosis (a blue or purple colour of the ears and extremities) prior to death.
Diagnosis of torsions is usually straightforward and can be made at post-mortem examination.
Pigs which have died from torsions may have swollen abdomens and congestion of the carcass. Care should be taken when opening the abdominal wall as distension of the gut is such that any nick leads to rupture. In the case of gastric torsion, the stomach (sometimes accompanied by the spleen or a lobe of liver) is twisted clockwise about its root. In most small intestinal torsions, the portion of twisted bowel is obvious by its dark red colour. The mesenteric blood vessels are filled with blood and appear as black lines converging on the root of the mesentery (the membrane suspending the intestines) where twisting has taken place.
The unaffected pieces of gut appear normal, although the portion towards the stomach is often full of contents and fluid. In whey bloat, the whole mass of the large intestine is twisted around its root and the caecum is distended with gas. The reason for the twist may be found in some cases. Occasionally the twist unwinds during or after death, but the reddened intestine and blood vessels confirm its post presence. Similarly, rough handling of the carcase during transport can result in apparent torsions, but these can be distinguished by the absence of the intense red colour from the twisted organ.
Treatment is rarely given because of the sudden onset of the condition. It is technically possible to operate and relieve the torsion. In some cases, animals seen to be distressed with suspected abdominal accident can be made to walk gently and the twisted bowel may straighten. Tranquillisers may also relax the bowel. Gastric torsion can be prevented by feeding twice daily, preferably rapidly, using automatic feeders. Whey bloat can be reduced by diluting whey so that less fermentable carbohydrate reaches the hindgut. Growth rates are reduced and there is pressure to use the highest concentration possible without causing deaths.