Abdominal distension may be due to pregnancy, abnormal accumulations of food, gas or fluid in the abdominal cavity or herniation of the abdominal wall.
Important causes in export cattle include:
A general physical examination should be performed including palpation, percussion, ballottement and paracentesis.
Differentiation is based on history (in particular the numbers affected, the suddenness of onset and feeding conditions) plus clinical examination and necropsy findings.
When viewed from the front or rear of the animal, distension may be unilateral, bilaterally symmetrical, asymmetrical or more prominent in the dorsal or ventral half depending on cause.
Passing a stomach tube, auscultation with percussion and ballottement to detect areas of gas and fluid, insertion of a trochar, rectal palpation (cattle) and examination of faeces may assist in deciding the cause and need for intervention.
Abdominal distension due to pregnancy is usually due to the presence of multiple foetuses. The rumen will distend after rapid engorgement on grain (grain overload) or slow accumulation over days of indigestible roughage (rumen impaction). If the distension is mainly gas, it will usually be free gas or froth in the rumen (gas cap or frothy bloat). If it is gas and fluid it may be a gastrointestinal accident such as torsion, obstruction or perforation of the abomasum or intestine. In goats it may be intestinal tympany of enterotoxaemia. Distension by fluid may be urine in a distended bladder or free in the abdomen after bladder rupture following urinary obstruction. Fluid may also be ascites if blood is chronically low in protein from parasites or undernutrition. Hernias should be considered in sheep and goats because the abdomen is thin walled and easily traumatised.
This will depend on the diagnosis. Pregnancy and bloat are treatable. Most other causes have a poor prognosis under live export conditions.
Preventative measures will depend on diagnosis and risk factors.