(a) The Brittle Hoof.
Definition. - As the name indicates, we have in this condition an abnormally dry state of the horn.
Symptoms. - These are obvious. The horn is hard, and when cut by the farrier's tools gives the impression of being baked hard and stony, the natural polish of the external layer is wanting, and there is present, usually, a tendency to contracted heels. With the dryness is a liability to fracture, especially at points where the shoe is attached by the nails. As a consequence, the shoes are easily cast, leading to splits in the direction of the horn fibres. These run dangerously near the sensitive structures, giving rise in many cases to lameness. Even where pronounced lameness is absent the action becomes short and 'groggy,' and the utmost care is required in the shoeing to keep the animal at work.
Causes. - To a very great extent the condition is hereditary, and is observed frequently in animals of the short, 'cobby' type. In ponies bred in the Welsh and New Forest droves the condition is not uncommon, especially in the smaller animals. Animals who have had their feet much in water - as, for instance, those bred and reared on marshy soils - and afterwards transferred to the constant dryness of stable bedding, are also particularly liable to this condition. It is noticed, too, following the excessive use of unsuitable hoof-dressings, more especially in cases where coat after coat of the dressing is applied without occasionally removing the previous applications.
Treatment. - As a prophylactic, a good hoof-dressing is indicated. It should not consist solely of grease, but should have mixed with it either wax, turpentine, or tar.
Above all, careful shoeing should be insisted on, and the owner of an animal with feet such as these will be well advised if he is recommended to have the shoeing superintended by one well competent to direct it rightly. The foot should be trimmed but lightly, always remembering that in a foot of this description the horn, in addition to being brittle, is generally abnormally thin. Jagged or partly broken pieces should be removed, and the bearing surface rendered as level as possible. The foot should be carefully examined before punching the nail-holes in the shoe, and the nail-holes afterwards placed so as to come opposite the soundest portions of horn. The nails themselves should be as thin as is consistent with durability, and should be driven as high up as possible.
On the least sign of undue wear the shoes should be removed, never, as is too often done, allowing them to remain on so long that a portion breaks away. If, with the laudable idea of not interfering with the horn more than is possible, this is practised, the portion of the shoe breaking off is bound to tear away with it more or less of the brittle horn to which it is attached.
Where the breaks in the horn are so large as to prevent a level bearing for the shoe being obtained, the interstices should be filled up with one or other of the preparations made for this purpose. One of the most suitable is that discovered by M. Defay. By its means sand-cracks or other fractures of the horn may be durably cemented up.
'Even pieces of iron may be securely joined together by its means. The only precaution for its successful application is the careful removal of all grease by spirits of sal-ammoniac, sulphide of carbon, or ether. M. Defay makes no secret of its composition, which is as follows: Take 1 part of coarsely-powdered gum-ammoniac, and 2 parts of gutta-percha, in pieces the size of a hazel-nut. Put them in a tin-lined vessel over a slow fire, and stir constantly until thoroughly mixed. Before the thick, resinous mass gets cold mould it into sticks like sealing-wax. The cement will keep for years, and when required for use it is only necessary to cut off a sufficient quantity, and remelt it immediately before application. We have frequently used this cement for the repair of seriously broken hoofs. It is so tenacious that it will retain the nails by which the shoe is attached without tearing away from the hoof.'[A]
[Footnote A: Veterinary Journal, vol. iii., p.71.]
Failing this, the bearing surface may be made level, and fractures repaired by using the huflederkitt described in the treatment of pumiced sole.
(b) The Spongy Hoof.
Definition. - This is the opposite condition to the one we have just described, and is characterized by the soft and non-resistant qualities of the horn.
Symptoms. - Spongy hoof is quite common in animals that have large, flat, and spreading feet - in fact, the two appear to run very much together. It is a common defect in animals reared in marshy districts, and of a heavy, lymphatic type. The Lincolnshire Shire, for instance, has often feet of this description, and, the causative factors being in this case long-continued, render the feet extremely predisposed to canker. The horn is distinctly soft to the knife, and has an appearance more or less greasy. Animals with spongy feet are unfit for long journeys on hard roads. When compelled to travel thus, the feet become hot and tender, and lameness results. A mild form of laminitis, extending over a period of three or four days, often follows on this enforced travelling on a hard road, more especially in cases where the animal is 'heavy topped,' and the usual food of a highly stimulating nature. In fact, it has been the author's experience to meet with this condition several times in the case of shire stallions doing a long walk daily upon hard roads, with the weather hot and dry.
Treatment. - When a horse with spongy feet is shod for the first time, care must be taken to avoid excessive paring of the sole, for already the natural wear of the foot has been sufficient to keep the soft horn in a state of thinness. For the same reason hot fitting of the shoe must not be indulged in for too long a time. That common malpractice of the forge, 'opening up the heels,' must, in this case, be especially guarded against, or the excessive paring of the frog and partial removal of the bars that this operation consists in will lay the foot open to risk of contraction. To begin with, the heels are naturally weak, and, once the bars are removed, there is nothing to prevent them rapidly caving in towards the frog. Even when carefully shod, a foot of this class is readily prone to contract directly the animal is brought into the stable, and the horn commences to dry to excess. An ordinary light shoe should be used, and the nails should be light and thin. They should be driven carefully home, and the 'clinching' made as tight and secure as possible.