It is not far from the truth to state that there are few horses in active work whose feet are not more or less contracted. In saying so much, we are not overlooking the fact that horses' feet vary considerably in form and size in different individuals. Some are large, low at the heels, and otherwise weak, while others are narrow and deep and upright, with great strength and thickness of horn. Among the latter are found examples conspicuous for their length from before backward (mule feet), and also for their narrowness. Animals having feet of this conformation are not infrequently regarded with suspicion, and are even sometimes condemned as being the subjects of disease and consequent deformity. It is, however, the opinion of most experienced men that feet of this character and conformation, i.e. resembling those of the mule, are of all kinds the best and most enduring. As, however, we have previously observed, all, whether they be of one description or another, become more or less contracted under the influence of domestication and the abuses of shoeing (fig. 404).
It must be recognized that a certain measure of contraction is quite consistent with freedom from lameness and disease; but there can be no doubt that the persistence of such a state, and the conditions by which it is fostered, will sooner or later impair the general function of the foot and lay the foundation for structural change.
It needs hardly to be observed that in a state of nature the unshod foot enjoys the fullest liberty, and every part is free to act in unison with every other; indeed, under these circumstances the natural form and dimensions are maintained by a just proportion in the waste and repair of the healthy parts; but when, as in domestication, the balance of these two forces becomes upset, then it is that deformity and disease usurp the place of symmetry and health.
Fig. 404. - Normal Hoof and Contracted Hoof.
The causes that conduce to this unhealthy state are several, the first and most pernicious being the operation of shoeing.
Here the very means designed to defend the foot expose it to the worst forms of abuse, viz. removal of the frog or sole, cutting away the "bars", and rasping the surface of the crust. By paring down the frog, this all-important organ, by nature intended to meet the ground, and by so doing to open out the heels, is thrown out of action; wasting and shrinking, the consequences of inactivity of the mutilated parts, then soon appear, to be followed by obvious contraction. If, as is usual, the bars, which may be deemed to be the buttresses of the heels, are also pared and weakened, the mischief is profoundly aggravated; and it is still more so, when to these habitual evils of shoeing is added the equally grave one of rasping the surface of the crust. By this mischievous practice the natural defence against evaporation of moisture from the foot is removed and a state of morbid dryness induced, which not only conduces to brittleness of the hoof, but also to contracting of the already weakened heels.
Long-continued standing and forced rest, which some horses experience, broken only at intervals by short periods of exercise, lend themselves to this evil consequence by throwing the entire foot out of use. Inactivity, especially when accompanied by high feeding, sooner or later ends in abiding congestion of the feet. This is followed by wasting of the sensitive parts, contraction of the hoof, and slowly-developed lameness, the cause of which is seldom suspected. In presence of the abuses referred to, work, like idleness, brings about the same result. Removed from contact with the ground, the frog ceases to perform its natural office, and while both feet and legs endure the jar against which it was designed to protect them, it at the same time shrinks and wastes for want of work, ending sooner or later in atrophy, deformity, and disease. To avoid contraction of the feet, the frog must be allowed to come to the ground, the bars must be preserved in their natural strength, and paring the sole and rasping the surface of the crust must be forbidden. Long standing in stalls should, as far as possible, be guarded against, and where rest is to be unbroken, the shoes should be removed and the horse allowed his liberty, either in a box well littered with tan or peat-moss, or in a yard or soft pasture where every part of the foot would be brought into action. On the Continent, and more recently in England, mechanical contrivances have been devised and applied with the object of restoring contracted feet to their normal condition. The means employed for this purpose is a shoe made with two movable heels having on the foot surface a small sloping wedge which is brought to bear on the inner sides of the heels of the foot, and then by means of an expanding screw passing from one heel of the shoe to the other outward, pressure is made on the parts, and by increasing the force from time to time the heels are caused to open. It need hardly be said that the change brought about in this way can only be temporary, and may be mischievous. As the foot contracts by wasting, so it must expand by growth, and to render the change permanent there is necessary the exercise of those natural forces which regulate its vital activities and conduce to re-establish in it a condition of health.