Definition. “A form of indigestion, of which the prominent feature is the drying and impaction of the ingesta between the folds of the third stomach. It may seem to be a primary disease, but in very many cases it occurs as a result of some acute febrile or inflammatory affection.” (Law’s “Veterinary Medicine,” Vol. II. p. 123.)
Synonyms. Dry murrain, clew-bound, fardel-bound, stomach staggers, grass staggers, vertigo, chronic dyspepsia, chronic indigestion.
Causes. Torpidity of the omasum, suppression of salivary secretion, with absence of “waves of liquid floating the finely divided food from the mouth or rumen to third stomach, are prime conditions of desiccation of the contents.” The third stomach, like the first and second, has no provision for liquid secretion, and depends for its supply on constant flushing by swallowed fluids. Therefore, if feeding and rumination are arrested and salivary secretion is suppressed, and if movements of the rumen and resulting overflow into the third stomach are checked, the ingesta of the third stomach, compressed between its folds, becomes drained of liquid and converted into a powder or dry mass. All febrile and inflammatory affections tend to this end, and more or less drying, with impaction of the contents of the omasum, is a constant feature in such cases. But in the majority of cases this condition is to be looked on as a secondary or subsidiary affection, and the real disease must be sought elsewhere.
The explanation of the susceptibility of the third stomach in constitutional troubles has been sought in the source of its innervation. Electric stimulation of the vagus rouses the movements of the first and second stomachs, but not those of the third. Action of the third stomach is excited by stimulation of the spinal cord, and of the sympathetic nervous branches going to the ganglionic cells in the walls of the omasum (Colin and Ellenberger). Its nerve supply coming from a different source, derangement of its function may occur independently of antecedent disorder of the first or second, and its motor supply coming from a source so closely related to the vaso-motor centres, perhaps affords some explanation of the connection of disorders of the omasum with febrile and inflammatory diseases.
Food is an important cause. Impaction of the omasum is a winter disease—the time of dry feeding. Dry, fibrous, innutritious fodder, and scarcity of water contribute to its production. It attacks cattle in spring or autumn on pastures in which fresh grass grows among the dead, dried, or withered stems of a previous growth. It occurs when stock are fed on corn or corn stalks (maize stalks) affected with smut or ergot, or on cereals or grasses similarly damaged, and in both cases especially when the water supply is deficient or restricted.
Sheep and goats, which habitually drink little, suffer less than do cattle, which drink freely.
Other causes. Fermented foods, microbian ferments and their products, which tend to induce torpidity of the omasum, fever, and lessened secretion of saliva, with diminished supply of liquid from mouth or rumen.
Pericarditis, by causing vascular stasis in the omasum, may induce torpor and impaction.
Lead poisoning paralyses action and favours impaction. Finely divided food stuffs—meal and bran—eaten greedily, may pass in quantity directly into the omasum and induce impaction. “The most acute and fatal forms occur in connection with a sudden change from dry to rich, luscious, green food in spring, the unwonted stimulus giving rise to general irritation of the whole gastric mucosa, with disordered and impaired function of all four stomachs, but especially of the third. Such cases are usually congestive and inflammatory, and the suspension of the gastric movements is a grand cause of impaction. In such cases, too, the brain or spinal cord, or both, are seriously involved, and the early death is preceded by torpor, paralysis, violent delirium or convulsions, following largely the type of acute lead poisoning.” (Law, loc. cit.)
The symptoms depend on the degree of impaction, and vary from simple, irregular, or suspended rumination to severe gastric and nervous disorder. The less acute cases are marked by failure to re-establish regular rumination or partial convalescence from fever or inflammation. The fever subsides, but the appetite remains capricious, the muzzle dry, eyes dull, spirits low, and breathing accelerated; the condition is sometimes accompanied by moaning. Slight tympanites may appear, and the contents of the rumen may feel solid, the mouth hot, clammy, and fœtid. The bowels are constipated, the fæces small in quantity, hard, covered with mucus or blood-streaked, and containing particles of undigested food; in other cases diarrhœa may set in, to be followed later by constipation. Alternations of constipation and diarrhœa may be repeated again and again. Exploration by pressure of the closed hand over the omasum will give an impression of solid resistance. There may be slight shivering, the ears and limbs are cold, the hair is erect in patches, dry and lustreless.