As many of you know, the foot is a common source of lameness; up to 90% of lameness can be located within the foot. The heel region of the foot can be blamed for up to 1/3 of chronic (long-term) lameness. This makes sense, as the hoof is the part of the body that receives and dampens a large amount of force during locomotion. It is estimated that the hooves bear 2-3 times the weight of the horse at a gallop in a straight line and between 5-10 times the body weight when cornering at a gallop. This means one hoof can be exposed to forces of up to 5000kg for an average sized horse. It is of no surprise that accurate trimming and shoeing of horses is one of the most important influences on the long-term soundness of a horse. Try going for a run-in pair of shoes 3 sizes too big… or maybe even in a pair of heels!
When trimming or shoeing a horse, emphasis should be placed on maintaining natural balance, combined with optimum length of toe and correct angulation of the hoof wall and pedal bone, relative to the pastern.
The angle of the hoof capsule and coffin bone should ideally be parallel to the angle of the pastern (the Hoof-Pastern angle). This helps the horse to evenly distribute its weight in the forelimb. If the angle becomes too low, when the toe becomes too long and the heel too low (broken back), more stress will be put on the structures at the back of the leg. Including the navicular bone, coffin joint, suspensory ligament, and flexor tendons. This greatly increases the chances of sudden injury, or gradual overloading type injuries to any of these structures e.g. a bowed tendon, chronic heel pain. If the angle is too high, an up-right conformation (broken forward), the fetlock, coffin joint and knee have more strain put on them leading to arthritic changes and lameness??
To illustrate this; break-over is a word commonly used in the horse world. It is the phase of the stride when the horse’s heel lifts off the ground and the time the toe is lifted. During this phase, the toe acts as a pivot point around which the heel rotates. The break-over point is the point where the heel lifts off the ground. Changes in toe length, hoof-pastern axis and hoof angle all affect the break-over. A long toe and low hoof angle will delay break-over as more time and effort is required to rotate the heel over the long lever arm that is the long toe. Optimising break-over is important.
A good farrier will always do his/her best to get the angles correct. However, it is not always as easy as it seems. A hoof that looks more or less in balance from the outside, can often have angles that are not quite right.
The only way to know for sure what the pedal bone (bone in the foot) is doing in relation to the hoof and pastern, is by radiographs (x-rays). Generally, two x-rays are taken, one from the side and one from the front. These radiographs can then be used by your vet and your farrier to ensure that your horse’s feet are in the best possible balance for his/her conformation. Hoof balance x-rays are now standard for many top-level horses throughout NZ.
Last season I dealt with a horse who was lame in both front feet. The horse looked to have reasonable hoof angles externally, however x-rays revealed a hoof pastern angle that was not perfect. We were able to work with the client’s usual farrier, to change the angles slightly. After two shoeing’s we had a sound horse!
We are now offering foot balance x-rays at a price of $290 for both front feet, sedation inclusive (if required) Please ring to discuss with one of our equine vets.
Mike Fitzgerald
