Suspicion of nailing should be entertained if the shoeing be recent, the hoof appear too small in relation to the body-weight, the walls have been thinned by rasping or have been broken away, or if the nails have been driven too high or very irregularly.
Causes.—The most common causes are mistakes in shoeing. In the majority of cases the cause is a disregard of the rule that the nails should penetrate the white line ([see pages 118], [119] and [130], heavy type). 1, using badly-punched shoes; 2, excessive paring and shortening of the hoof; 3, weakening of the lower border of the wall by excessive rasping away of the outside ([Fig. 187, c]); 4, mistakes in fitting the shoe, especially applying shoes that are too narrow, letting the toe-clips too deep into the horn, by which the nail-holes near the toe, instead of falling upon the white line, are carried back upon the edge of the sole, or using shoes in which the nail-holes are too wide or improperly directed; 5, using nails that are split, incomplete, badly formed and bevelled, and too large; 6, starting nails too deep or with the bevel on the outside, or drawing them too tight. As occasional causes may be mentioned: 7, old nail-stubs in the horn; 8, walls that are very thin or broken away; 9, a soft, crumbling wall, which alters the sound and feeling of the nail as it is driven, and makes it difficult to judge of its course; 10, restlessness of the animal while being shod.
Examination.—Press with the hoof-testers upon the sole and clinches; tap lightly upon the clinches. If these acts cause pain, there can be little doubt that the nail is responsible for the damage. Remove the shoe by drawing each nail separately and carefully. Examine the nails with reference to their direction and size, as well as to staining with blood, blood-serum, or pus. Immediately after removing the shoe, look for the point of entrance of each nail into the hoof, and if a nail-hole be found upon the edge of the sole ([Fig. 187, b]) instead of in the white line, it is highly probable that the nail which passed in at that place pressed upon the sensitive tissues of the foot. Every nail-hole should then be searched by passing a clean new nail into it and pressing its point towards the soft tissues at various depths; any indication of pain caused by this act is pretty sure proof of nailing. It stands to reason that the character of the nail-holes in the shoe should be closely examined.
Fig. 186.
Cross-section of a shod hoof,
the hoof-skin or pododerm being
in red: a, indirect nailing
where backsetting has been
overdone and has bent the nail;
b, nail properly placed
and of correct shape.
Fig. 187.
Front hoof deficient in horn:
a, right position of the
nail-holes in the white line;
b, faulty position inside
of the white line; c, wall
weakened by excessive rasping.
Treatment.—When the foot has sustained an ordinary simple prick with a nail, the latter should be left out and the hole well filled with wax. As a rule, no serious results follow. In severe direct nailing the entire shoeing should be most carefully examined, and only after everything is found to be right, and the shoe fits in such a manner that the nails can only penetrate the wall from the white line, can it be regarded as correct. The offending nail-hole is then to be closed with wax. According to the intensity of the wound we may expect a more or less pronounced inflammation of the pododerm, and this is to be combated by resting the animal and cooling the foot.