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The
Natural Horse Group was established in 2001.
It aims to provide
information that enables people to explore ways of keeping and managing
equines that enhance wellbeing and encourage a natural lifestyle
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Articles
Optimising the Equine Hoof
By Les Spark
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Last year Jasper finished his first full barefoot competition year by finishing 5th in the Red Dragon 2 day 100 miles Endurance Race. He did 10 rides in a range of footing conditions and was never lamed out even when other riders complained of hard ground. Tiffany our ageing TB completed 3 days at the Lindum ride and two TREC competitions. Jasper has completed a 40 km and 65 km rides this year so far, again without a hint of lameness.
I have put a great deal of thought into how we can optimise the foot for this hard competition work and would like to take this opportunity to share my thoughts with you all. If we can understand how the horse evolved this amazing foot we can then perform the best possible trim. What I am about to discuss is not light reading so put the grey matter into gear and get your mind inside that foot! Also if you have books with hoof diagrams get those out too.
The foot is primarily a deliverer and acceptor of force. Every force has an equal and opposite force so the foot experiences the force of the equine body in movement and the reaction force of the ground pushing against the foot. The body acts through the bones towards the ground and ground towards the bones through the hoof capsule, this generates a shear force (a scissor action) in the hoof capsule between the coffin bone and the outer wall. When the horse stands or moves, that shear force is always there to a lesser (standing) or greater (jumping) extent.
The structures of the hoof have evolved to handle and minimise this shear force. It has done this by creating a massive surface area not only in the lamella but also in the coffin bone (find a coffin bone x-ray picture and note the ‘airy’ structure). This structure not only 'glues' the capsule and bone together with bio-adhesive (boiled hooves make great glue) but it grows to replace wear and responds to increases in stress by toughening the structure (like our skin responds to hard work). If this glue starts to yield under the shear forces the foot is heading for trouble, slowly or quickly.
As I see it there are two types of shear the hoof has to handle. One from the mass of the horse’s body as it moves, it is low frequency (walk, trot, canter) and has the full force of the horses movement, lets call it type A. The other is high frequency with small movement and generated when the hoof hits the ground, type B say.
Type A is handled by the suspensory system in the lower leg and much like a car suspension has a spring (suspensory ligament) a damper (comprising: digital cushion, frog, lateral cartilages, blood vessels, blood). This lot works quite well on its own with the leg chopped of just above the knee or hock, even minus the blood. Some fancy control is added by the muscles of the tendons a bit like a computer controlled suspension system in some cars which soften or harden depending on the forces experienced at any instant.
Type B is, I think, handled in the foot. These jarring frequencies vary with the ground surface; for example, slapping your seat cushion is very different from slapping your desk with the palm and fingers of the flat hand. One hurts and the other doesn't. This jarring is absorbed in the materials of the hoof at the structural level. It is very interesting to note that the feral hoof does not contact the ground with the outer hoof wall (the trimmed mustang roll produces the same effect).
What has been noticed with domestic barefoot horses is that the hoof wall thickness increases towards that of the feral horse, the main thickening coming from the non-pigmented wall (sometimes called - the water line). This structure is less regular and contains more water than the outer wall. It is ideally suited to absorbing the jarring ground effects and converting them into heat, via microscopic structural distortion, the heat being carried away by the blood via the large surface area of the lamella corium. The feral mustang roll puts the waterline in contact with the ground to absorb this jarring shear.
A good sole is very much like the 'water line' and will have a similar ability to damp out shock of the foot hitting the ground. Being modified skin it responds to the work it gets. Put shoes or boots on and it will lose toughness. Put the sole in touch with the ground and it toughens up.
There is much argument about the validity of using the feral horse model for the domestic horse. There is however one thing which may be indisputable 'the feral horse keeps a balanced foot'. If it didn't it would wear the hoof unevenly and be dead meat. Let’s consider how this can be done. Given that there is consistency of material on the solar surface of the foot then to maintain even wear there should be no more pressure on the rear of the foot than there is on the front of the foot.
The forces from the horse’s movement all end up in the coffin bone joint when the foot contacts the ground. The forces must move through the foot as if the coffin bone joint was the peak of a cone and the ground contact surface of the foot the base of the cone. Under these circumstances all of the base of the cone will be under equal pressure against the ground. The force distribution cone does not follow the lines of the coffin bone as all the tissues in the foot are involved in the transmission of the force.
However the foot has a lump cut out for the frog and associated shock absorption equipment. With this uneven base the force at the centre of the cone cannot be evenly distributed so more pressure will be felt by the areas either side of the gap. If this cone were now scraped across a wearing surface it would wear most at the corners of the gap, the heels. This is why the bars must make contact with the ground; they provide the extra support on the ground and keep an even wear pattern on the hoof from front to back.
The horse left to its own devices in the environment it adapted to keeps a short stubby hoof. We humans have taken the horse out of its adapted habitat, which is harsh underfoot and placed it in nice soft pastures. The habitat in which the hoof evolved is gone! The forces stay the same, the genetics stay the same but the grinding ground has gone. The hoof is at a loss as it grows to match a wearing surface that it may never meet, a surface that wore the hoof to keep it balanced.
We must now take responsibility to trim the hoof so it is balanced to produce even loading on the ground. Once even loading is achieved and the horse ridden on rough ground often enough the hoof will stay balanced. If this cannot be done there will be a constant need to rebalance the foot as it continues to grow in its genetically programmed pattern. Committing to this task has the benefit of seeing and feeling a happier, freer-moving friend. |
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