What would cause a cows stomach to swell?

Answer 1

A cow's stomach has four compartments, each of which theoretically have the ability to dilate or swell. In practice, two of the four compartments are clinically significant in terms of dilation - the rumen (first compartment) and the abomasum (fourth compartment).

Dilation of the rumen is known to result from three processes: choke, bloat and vagal indigestion. Choke is the layman's term for an obstruction of the esophagus. The bacteria in the rumen produce about 2 L of carbon dioxide every minute, so it is vitally important that the gas be able to escape out the esophagus through eruction (belching). Choke prevents that gas from escaping, so it builds up in the rumen. After about one hour the gas has dilated the rumen to the point that it compresses the thorax severely enough to prevent the cow from drawing a breath and the animal will die of asphyxiation.

Bloat is the layman's term for gas build-up in the rumen. It can be caused by choke, but is more often a result of either too much protein in the rumen (which will cause frothy bloat where the gas is trapped in bubbles) or as a result of rumen overfill (which will cause free bloat where the gas is in a cap in the top of the rumen but cant' get down to the level of the esophagus to escape). Bloat is also immediately life-threatening and is treated either by oral administration of poloxalene which breaks down the bubbles or by drawing off the gas bubble through oral intubation, rumenocentesis or trocharization of the rumen.

Vagal indigestion is a result of damage to the vagal nerve, which innervates the rumen. Causes of the nerve damage are varied and often unknown in individual animals, but the result is the same: the rumen cannot contract to churn and move the ingesta in it, so the bacteria eventually die due to excessive concentrations of nitrates and other waste products and the animal suffers from malnutrition and dehydration.

The abomasum will dilate due to outflow obstruction caused by displacement of the abomasum and/or torsion/volvulus of the abomasum. The abomasum is not well secured in the ventral cranial abdomen and under certain metabolic conditions can become somewhat mobile. The more common displacement is an LDA, left displaced abomasum, where the abomasum 'flips up' along the left body wall on the outside of the rumen. The less common and more serious displacement is an RDA, right displaced abomasum. Here the abomasum 'flips up' along the right body wall and is prone to torsion (RTA), which often causes nerve damage and vascular obstruction to the abomasum as well as outflow obstruction. The correction for both is to get the abomasum back into the proper position on the ventral midline, either through rolling the cow or through surgical relocation.