124. Hoof Care...

Hoof Care I: Foot Conformation and Balance

Dr Tim Watson BVM&S, PhD, MRCVS of the Equine Veterinary Clinic, Turingingshaw Farm, Houtson, Renfrewshire

No one needs reminding of the old adage “no foot, no horse”. Foot and specifically hoof problems are a very common cause of lameness, particularly of the forelimbs, in all types of horses and can seriously affect the value and saleability of your horse. These problems can be divided into three categories, namely abnormalities of foot conformation and balance, infectious disease (white line disease and thrush), and poor horn quality. Abnormalities of conformation and foot balance are discussed in this article; how to recognise and deal with infectious disease and poor horn quality will be addressed in a subsequent issue.

Normal foot conformation and balance
The forefoot should be round in shape and wide at the heels, with a sole that is slightly concave from side to side and front to back, and a frog that is well developed with a good cleft. Ideally there should be no contact between the sole and the ground; the sole is not a weight-bearing structure. A line drawn through the centre of the frog should point to the toe and divide the foot into two equal halves.
When viewed from the side, the dorsal (front) hoof wall should be aligned with the pastern and make an angle of 50-60O with the ground. The angle of the heel should correspond to that of the toe. Viewed from the front, the angles that the lateral (outside) and medial (inside) wall make with the ground should be similar and the coronary band should run concentric with the ground.
Abnormal conformation of the fore feet can be associated with flat and, or, thin soles, contracted and, or, collapsed heels and problems with medial-lateral (side to side) and dorsal-palmar (front to back) foot imbalance.

Flat and thin soles
Flat soles lead to unrealistic bearing of weight and concussion of the internal structures of the foot, notably the pedal bone, and are a risk factor for the development of chronic foot pain and pedal osteitis. Horses with flat soles often have very wide or flared hooves, giving the impression that the structures of the foot have ‘sunk’ as structural support from the hoof walls has been lost. If this is the case, then efforts should be made by the farrier to reshape the foot, removing the flares and fitting a shoe with side clips to prevent further expansion, and to fit a silicon or leather pad under shoe to protect the sole from concussion.
Flat soles are often associated with a weak hoof structure, which may be genetic or nutritional in origin or result from unusually high moisture content in the hoof. For this reason, I would recommend a good quality hoof supplement providing the essential nutrients for horn growth, specifically biotin, methionine and zinc. I don’t usually recommend using a hoof-hardener in these cases since making the sole harder will reduce the ability of the sole to cushion the internal structure of the foot from concussive forces.
Thin soles should be managed similarly, using a good nutritional supplement to improve horn quality and growth, and protecting the soles by fitting pads as required. If the soles are simply thin but otherwise concave and non-weight bearing, then I do recommend a hoof hardener to increase the resilience of the sole and protect the foot from stones and uneven ground.

Contracted heels
Contraction or narrowing of the heels can be caused by reduced use of the foot, for instance when the limb is injured and non-weight bearing for a period of time, or a long-toe low-heel foot shape. One or both heels of a foot can be contracted; this can be assessed from the width of the heels at the buttress, which should be similar to that of the hoof approximately 1 inch back from the toe. When a limb is under-used for a period of time, there is a reduction in the blood flow to the foot, causing a drop in moisture content of the hoof capsule, and a lack of pressure from the weight of the horse during movement that would otherwise expand the heels. In horse with long toes, the hoof elongates from toe to heel and the heels generally move closer together.
Contracted heels should be dealt with by first identifying and treating any underlying lameness, such that there is a return to normal weight bearing and movement, and then using an appropriate ‘hoof sealer’ to help retain moisture and prevent drying while having your farrier shoe the horse to allow for expansion of the heels.

Dorsal-palmar foot imbalance and under-run heels
Dorsal-palmar foot balance refers to the angle that the dorsal wall of the hoof makes with the ground. If this angle is too low, an imaginary line drawn parallel to the hoof wall through the centre of the pastern will be broken backwards at a point near the coronary band. Collapsed or under-run heels are commonly found in horses with dorsal-palmar foot imbalance (so-called long-toe low-heel conformation) and are identified by viewing the foot from the side, whereby it is obvious that the heels are short as the coronary band sits close to the ground and the angle of the heels to the ground is more acute that the angle of the toe.
Dorsal-palmar foot imbalance with a broken back hoof-pastern axis and under-run heels results in increased load-bearing of the palmar (back) structures of the foot and can lead to corns and abscesses, as well as placing excess strain on the flexor tendons and ligaments and increasing the risk of the horse developing of navicular syndrome. It is thus very important that this conformation is corrected by appropriate trimming of the foot and support of its palmar structures.
The toe of the hoof wall should be trimmed as short as is practical, often ‘squaring’ the toes to move the break-over point further back. The heels should be taken down only enough to obtain a good load-bearing surface of healthy horn and then shod so that there is more rearward support for the heels. This inevitably means fitting a shoe that overhangs the back of the heels, making it liable to be lost if trodden on by a back foot – this can be prevented by fitting the largest possible over-reach boots to the from feet.
Support for the heels can be improved by using a bar shoe, which spreads the weight bearing across the back of the frog and so reducing compressive forces that would otherwise counteract heel growth. The palmar structures of the foot can also be protected by fitting shoes (or inserts) with a wedge, which effectively raise the heels and so reduce strain on the flexor tendons and associated ligaments. Growth of healthy heel horn can be helped by the feeding of good quality nutritional supplements, together with the application of hoof oils or sealers that help the horn retain moisture and hence structure.

Medial-lateral foot imbalance
Medial-lateral foot balance refers to the relationship between the inside and outside walls of the foot. In trimming a foot, the goal is to achieve a ground surface that is centred beneath the limb and so allowing the hoof to bear the weight of the limb evenly. When there is imbalance, the weight is not evenly distributed and this can lead to excessive concussion of one side of the foot and consequent lameness. Medial-lateral imbalance can be detected by examining the symmetry of the hoof walls when viewed from the front, the extent to which a line drawn through the frog bisects the sole of the foot into two equal sized and shaped halves, and whether the foot lands evenly on both inside and outside walls when the horse walks.
Of all the abnormalities in hoof conformation and structure, medial-lateral imbalance is perhaps the easiest to fix, requiring appropriate trimming of one side of the foot to achieve normal balance. This said, problems can be encountered when there is outward or inward deviation of the limb, such that the foot does not sit squarely at the end of the limb, or when there is a twist in the lower limb. Such cases may require building up of one side in addition to trimming of the other side of the foot.

End note
The correction of abnormalities of foot balance and conformation requires the expertise and skills of a farrier. The views presented in this article represent those of the author and the management of individual cases is best achieved by close collaboration of owner, vet and farrier and the application of appropriate investigative and diagnostic techniques to fully characterise the abnormalities requiring attention.