Causes. These are to a large extent the same as those of gastric tympany. General and digestive debility resulting from former disease, from spare diet, from unsuitable or indigestible food, from anæmia, from parasites, from hemorrhages, is a potent predisposing cause.
Weakness of the alimentary canal from catarrh, or other persistent disease, from impaired innervation, from embolism of the vessels and imperfect circulation also predisposes, or again the lack of vermicular movement and of the mingling of the digestive fluids with the food, leaving the latter in a specially fermentescible condition. As direct exciting causes may be named:
Very fermentescible food in excess, such as the leguminous products (beans, peas, vetches, cowpea, alfalfa, sainfoin, clover) in their green condition. These contain an excess of protein compounds, which should be mainly digested in the stomach, and if passed rapidly in large quantity into the intestines, they fail to be sufficiently acted on by the trypsin, and are specially liable to fermentation. Very rapidly grown and aqueous grasses are similarly liable to decomposition.
New grain is specially liable to fermentation the more so that it sometimes contains a paralyzing agent, which acts like intoxicating ryegrass. The ripening seeds of many forage plants often act in this way, (annual and perennial ryegrass, millet, Hungarian grass, chick vetch, vetches generally). The same has been observed of the leaves of growing maize, grapevine leaves, and potato plants.
Musty and spoiled fodders of all kinds are very dangerous, the toxic principles of the fungi and bacterial ferments paralyzing the sympathetic nervous filaments.
Fodders that are imperfectly masticated and insalivated owing to defective teeth or diseased jaws or glands are liable to prove hurtful in a similar way.
A full drink of water and especially of ice cold water after a feed of grain is one of the most potent factors. The stomach and intestines are both roused to violent peristaltic action, the undigested food is washed on into the bowels, and too often the action of the cold induces congestion and partial paresis, and exposes the undigested mass to the uncontrolled action of ferments.
Circulatory troubles caused by verminous embolism (see intestinal congestion) is another very prolific factor. A sudden chill in an animal that is perspiring and fatigued may precipitate an attack, by causing a retrocession of blood from the skin to the intestines, with resulting paresis of their coats.
Symptoms. The condition is usually complicated with gastric tympany, so that we have a complication of symptoms. The history of the case is often diagnostic, showing one of the above mentioned causes, and above all a full drink after a feed of grain, speedily followed by abdominal pain, gaseous distension of the abdomen, causing death in two hours or upward. The distension of the abdomen usually shows more on the right than the left, and the resonance on percussion is greater. Colics are usually less violent than in intestinal congestion, and the actions of the animal are less precipitate or disorderly. He may lie down, roll and rise, but the constant restless movement, the sitting on the haunches, and the frequent agonized turning of the nose toward the flank are rarely shown. The animal is rather dull and prostrate, passing finally into a stupor, the face is pinched and anxious, the back arched, the head pendent, the walk slow and unsteady, and respiration and pulse accelerated. There is no complete intermission of pain, though it is more acute at one time than another, for some time there is rumbling in the bowels followed by complete silence, as they are fully paralyzed, fæces may be passed at first, but this ceases as the floating colon is emptied and the gaseous distension becomes extreme, and urination which may take place in the early stages is no longer effected in the advanced ones. The compression of the thorax causes severe dyspnœa, accompanied, when the patient is down, by a slight groan.
Course. In the advanced stages the animal may sink to the ground oppressed by the shock, poisoned by the carbon dioxide which can no longer be exhaled through the lungs, and by hydrogen sulphide and other toxic products of intestinal fermentation. Death may follow two hours after a hearty meal and is rarely long delayed in fatal cases.