The first of these operations, the technique of which scarcely requires description, is often of little value; for the solids and liquid contents of the rumen being permeated with gases, rise as a fermenting mass into the upper portions of the rumen, and continually obstruct the open end of the catheter, so that very little gas escapes.
Puncture of the rumen is much more effective and easier to perform. The owner himself often operates with an ordinary pocket knife, sometimes introducing a couple of fingers or a short length of elder-wood tube into the wound thus produced.
The incision should be made at one stroke, for any hesitation may cause the wall of the abdomen to recede from the rumen, which lies immediately below. Should gas escape under the skin, emphysema, which often extends to the loins and along the quarters, may be produced, and may be followed by diffuse subcutaneous suppuration, resulting from pyogenic germs entering the subcutaneous tissue.
Large quantities of gas escape from the puncture, sometimes with such force as to drive out the canula. The flow of gas then ceases. In other cases the tube becomes blocked; because, as the pressure within the rumen diminishes, the gases dissolved or mixed with the partially digested food are freed, and the whole contents of the rumen become converted into an aerated, bubbling mass. Liquid or semi-liquid materials may be ejected to some distance, or may pass between the skin and the muscles, or between the walls of the rumen and the abdomen, producing various complications, like necrosis, abscess formation, etc. Such accidents can be avoided by exercising firm pressure with the fingers on the tissues surrounding the canula.
Even when the rumen has resumed its normal size recovery is not certain, and may not occur for several hours, or even several days, afterwards. The patients should therefore be kept under observation for some time, and it is usually best to leave the canula in place for one or two days, and to put the animal on low diet.
Necrosis of aponeurotic tissues, fistula formation, and local peritonitis only occur if the instrument is dirty or is introduced in a wrong direction.
IMPACTION OF THE RUMEN. INDIGESTION AS A RESULT OF OVER-EATING.
In this condition the rumen is over-distended with food. The symptoms are principally due to abnormal fermentation, the peristaltic action of the rumen being in abeyance, and the food failing to pass towards the omasum and abomasum. Rumination is generally suppressed.
The disease usually follows change of diet. When the diet has long been restricted, as occurs during years of bad harvests, and animals are afterwards set at liberty in rich pastures, they eat greedily, distend the rumen with large quantities of green fodder, and set up all the necessary conditions for this form of indigestion. Similar results follow when gluttonous animals are freely supplied with rich food. Working oxen also suffer if withdrawn from work and fed with roots, beetroot refuse, brewers’ grains, or other manufacturing residue for the purpose of fattening. These materials can only be absorbed in moderate quantity, and the large amount of water, etc., they contain is apt to disturb the animal’s digestive powers, while owing to its fine state of division such food cannot be returned to the mouth for secondary mastication, and rumination therefore remains incomplete: the food accumulates in the rumen, distending and eventually paralysing it. This is a common result of feeding on semi-liquid pulp, which in order to be ruminated should be mixed with rough forage.
Insufficiency of drinking water is another and more frequent cause, especially during the winter, because the ox-herd or cowman is often too lazy to give a regular and sufficient supply unless water is laid on in the stable itself. The dry food becomes compacted into a mass, which cannot be returned to the mouth for rumination. Moreover, less saliva is then secreted, and Colin has shown that rumination is impossible when the parotid ducts are ligatured.