General symptoms. As soon as the foreign body becomes fixed in position, the animal begins to make exceptional efforts to swallow. The head is extended on the neck, and the œsophagus and the muscles surrounding the trachea are violently contracted. These efforts proving fruitless, feeding is necessarily stopped, and the animal at once appears slightly anxious.
Very soon afterwards salivation sets in, saliva being continuously secreted. If the obstruction is total, the saliva cannot be swallowed, and is either returned in quantities by antiperistaltic movements or escapes in frothy filaments from the mouth.
Tympanites is not long in appearing. It is progressive, and results both from arrest of eructation and from continued fermentation in the rumen. It may eventually come to a standstill, or may continue and threaten to produce asphyxia.
Local symptoms. The local symptoms are difficult to appreciate, except in cases of cervical obstruction. Sometimes the foreign body produces a local swelling, which changes the outline of the jugular furrow, most frequently on the left side. In many cases it can only be detected by manipulating the parts between the trachea and the lower surface of the cervical vertebræ. When the obstruction is within the thorax, the probang alone can detect its position.
Diagnosis. The diagnosis is usually easy. The history and the observed symptoms are often very clear, and the suddenness with which the obstruction has made its appearance prevent the condition from being confused with dilatation or stricture.
The prognosis is very variable. It is often easy to remove the obstacle; in other cases intervention is difficult, and death may occur rapidly.
Treatment is confined to one essential point—removal of the obstruction. The chief difficulty lies in choosing the mode of intervention. Moreover, success depends on several factors, which, in the order of their importance, are as follows: the size of the obstructing body; the time which has elapsed since the accident occurred; the bodily condition of the animal—i.e., whether it be fat or thin—and the extent to which tympanites has developed.
The first thing to do (and in favourable cases all that is required) is to puncture the rumen and leave the canula for some time in position. The onward progress of the foreign body, especially when the obstruction is in the intra-thoracic portion of the tube, is often impeded by the tympanites, which tends to thrust the object towards the pharynx, or at least to fix it in position. In consequence of a sudden change in the conditions of pressure the foreign body may move and pass into the rumen; all danger is then at an end.
Even though the obstruction does not immediately cease, puncture of the rumen, by removing the danger of asphyxia, allows one at least to wait for several hours, sometimes until next day, during which time the object may pass into the rumen without further extraneous assistance. The other methods may be grouped into four series:
I. External taxis. This is directed towards loosening the foreign body and thrusting it towards the pharynx and buccal cavity. It can only be used against obstructions in the cervical region. Two methods, although very ancient, are still practised.