CARE OF THE HOOF CAPSULE
Robert A Eustace FRCVS
The hoof horn of normal horses is remarkably resistant to infections considering the environment they inhabit. However, it seems that horn infections are becoming more common, at the Laminitis Clinic we see more than we did 10 years ago. By horn infections I mean the likes of seedy toe, white line disease and onycomycosis, these are dry infections. This is opposed to pus in the foot infections which result from different types of bacteria which usually enter the foot from a penetrating wound. It is worthwhile considering some of the factors which may be influencing this change.
Unless stables are kept clean they soon become an ideal environment for infective bacteria and fungi to thrive. Good stable management is therefore essential to keep the bedding clean and dry. A well drained stable with a solid floor is recommended. The other important consideration is the type of bedding. There is a greater variety of bedding systems available now than there ever have been. As far as I am aware none have been shown to be significantly better than others. As a general principle however I recommend an absorbent bedding which keeps a soft yielding covering for the horse to stand on. At the Laminitis Clinic we have always used dry clean whitewood shavings. Despite trying most other types of bedding material this is what we continue to use. I am not in favour of rubber matting as unless it is expertly fitted and maintained it tends to lift from the underflooring and trap pockets of water and urine. Some matting is slippery and few horses, in my experience, prefer to lie on a rubber mat in preference of a proper bed. If horse urine and faeces are left in the stables considerable volumes of ammonia are produced. Ammonia both damages the horn, weakening the outer layer and encouraging the entry of organisms and irritates the horse's lungs.
A soft, dry, absorbent bedding which does not separate as the horse moves about is recommended on a well drained non-slip floor. The use of a hoof dressing which neutralises the damaging effects of ammonia is recommended.
There is no doubt that what you paint on the feet can have a real effect, for good or ill, on the health of your horses feet. It should be remembered that the organisms which infect horn are all anaerobic, that is they cannot live in the presence of oxygen. Therefore if you smother the feet in an oil or grease which does not let oxygen through to the wall you have created an ideal environment for these horn eating bacteria and fungi.
Similarly if you apply dressings which contain chemicals which damage the horn this will weaken the horses resistance to infection. Any dressing which smells strongly or is irritant to your own skin, is not recommended for use on hooves. This includes oils, tars and dressings used to harden the horn.
Although the horse needs a strong hoof capsule, it should not be a particularly hard hoof as this means that it has lost its pliability and along with it, the ability to cushion the sensitive structures inside the foot from the concussion of daily work.
A hoof dressing which contains no strong chemicals, does not exclude oxygen and does not alter the horn is recommended. The dressing should have both antifungal and antibacterial properties.
The state of hydration of the foot affects both its strength and its ability to withstand infection. Wet horn is weak horn. Horn digesting organisms do not thrive in dry conditions. In our climate the problem is usually one of alternating wet and dry conditions which tend to make the horn swell and shrink and predispose to surface cracks and infection.
A hoof dressing which helps keep the horn at a relatively constant state of hydration is recommended.
Diseases predisposing to horn infections.
Undoubtedly, the most common is that of laminitis and founder. Even sub-clinical laminitis, in which the horse does not move well, but is not obviously lame (to the untrained eye), will result in weakening of the hoof around the white line.
Chronic founder cases always have abnormally wide white lines around the front part of the foot and are always at higher risk of horn infection. This is particularly true in foundered donkeys where seedy toe is epidemic.
Any wounding to the coronary band or hoof wall will allow the entry of organisms which will digest the horn.
Inadequate nutrition which does not provide all the essential micronutrients for correct horn production will result in a weaker hoof capsule which is susceptible to infections.
Some animals seem to have a genetic inability to produce normal hoof horn. For example we have seen three Connemara ponies (apparently unrelated to one another) which have been unable to incorporate the normal lipids into their hooves. This has resulted in chronic, extensive horn infections which have ultimately resulted in the affected animals having to be put down.
At the Laminitis Clinic, we use two hoof care products, which combine all the above recommendations with non of the drawbacks:
The first product we use to prevent horn infections and damage from ammonia from stable bedding. This product also keeps the hoof capsule pliable and does allow oxygen to penetrate through to the hoof horn. It contains no strong chemicals and does not alter the hoof horn itself. It has both antifungal and antibacterial properties and helps keep the horn at a relatively constant state of hydration.
When horses are suffering from hoof horn infections, we use the second product. This has enhanced anti-fungal and anti-bacterial properties and is highly penetrating, so that it can get to the root of the infection. As the infective organisms cannot survive exposure to oxygen it is usually necessary to remove all infected horn tissue and expose the underlying horn to the oxygen in the air. The lesions should be resected to the periphery until apparently sound horn is encountered. The feet are left unbandaged and a daily application of the hoof disinfecting product is applied.
In severe cases the horse may have to be completely stable rested on a deep dry shavings bed until the new hoof horn has grown down to the ground. In less severe cases glue-on shoes may be necessary. It is vital not to cover the lesions in any form of hoof filler (artificial horn) as this excludes the atmospheric oxygen and predisposes to extension of the infection.