A, Defay’s shoe for
expanding the quarters
of a hoof; a, clip
apposed to the buttress;
b, slot sawed at the
toe to weaken the shoe;
B, screw for expanding
the Defay’s shoe.
Contraction affects front feet, especially those of the acute-angled form, more often than hind feet. In order to determine whether or not a hoof is too narrow, we should always examine the frog and its lateral lacunæ. If the frog is small and narrow, and the lateral lacunæ very narrow and deep, there can be no doubt but that the hoof is too narrow (contracted).
The causes, aside from too little exercise, are chiefly errors in shoeing, such as weakening the posterior half of the hoof, leaving too long a toe, either neglecting to remove the spurs of horn which grow from the buttresses and press upon the frog, or removing them incompletely, and using shoes whose branches are either too wide apart or are inclined downward and inward, so that under the weight of the body the heels are squeezed together and contraction is favored.
Prevention and Treatment.—First, it should be borne in mind that whatever exercises moderate pressure upon the sole, frog, and bars tends to expand the hoof. The action and value of the various shoes, frog-, and sole-pads, are measured by this rule. For this reason a shoe with heel-calks is never advisable if an open flat shoe without other means of relief can be used. Furthermore, since contraction is the parent of nearly all diseases of the hoof (corns, quarter-cracks, bar-cracks, thrush of the frog), we should use the greatest care to prevent it by dressing the hoof as described on pages 98 to 103, using flat shoes with a horizontal bearing-surface for the quarters, giving abundant exercise, preventing drying out of the horn, and allowing the animal to go barefoot whenever possible. Where the contraction is but slight the foregoing rules will be found sufficient.
In very pronounced contraction, where the hoof is not acute-angled, an expansive shoe with clips raised at the ends of the branches to press against the buttresses may prove very advantageous; but under no conditions should violence be used in expanding the heels with the expanding-screw. This is an act of extreme delicacy, and should be performed only by experienced veterinarians.
In very pronounced contraction of one or both quarters of hoofs of every degree of obliquity we may obtain a continuous expansive action by the use of one of the numerous V-shaped springs, of which the Chadwick spring is the best ([Fig. 207] and [208]). After levelling the wall and thinning the branches of the sole, the points of the spring are set against the buttresses, the apex of the spring moved to and fro till the points have bored well into the horn, when the apex is laid against the sole at the toe, the sole filled with tar and oakum and covered by a leather sole, and a bar-shoe applied. If the contraction be less pronounced, or if the frog be much shrunken we may place a Chadwick spring beneath a rubber bar-pad with a short shoe. The spring may be stiffened from shoeing to shoeing, first by introducing the ferrule at the apex of the spring and later by shifting the ferrule toward the shoulder ([Figs. 207, b], and [208, b]).
Fig. 207.
The Chadwick spring for expanding
contracted quarters: a, apex
of spring; b, ferrule to
stiffen the spring; c,
point which is buried in a
buttress of the hoof.