By Roger Bourdon
You call the Vet because your horse has a hoof problem, and he asks for some information. What do you say? Do you know how to describe the parts of the hoof so that he might recognise the problem before he even gets there – thus saving a call out fee?
An army may march on its stomach but a horse definitely marches on its hooves.
I had the vet out the other day doing a routine check on my old boy and he had a good poke around in the hooves. Although he said they were in good shape for the horse’s age, it did make me wonder how much I knew about the hoof, because he started using terms that I didn’t recognise. So I had a little anatomy lesson on the spot but he did mention that few private owners (and I’m not talking riding stables here) could describe a hoof problem in other than the simplest terms, which meant he could seldom diagnose without a visit.
I have since put a new free bonus book up on my site on hoof related problems, so I thought I’d cover a few of the basic terms here, and then do a follow on article about hoof problems and diseases.
What are the different parts of the hoof called.
The walls are the protection for the softer internal tissues of the hoof- it’s like the human toe nail. They also provide grip on different terrains. They are elastic and very tough keratin-based substance, similar to a Teflon layer, the thickness is approximately 6 mm - 12 mm. It takes 9-12 months for the hoof to grow from the coronary band to the toe. In order for the horn to grow correctly and form a healthy foot, the horse must be provided with a good diet and be in good health. These factors must be checked if the horn starts to become brittle and weak or if the foot looks badly formed. A feed supplement of biotin may be helpful to promote good horn growth.
Three different layers make up the Wall: the pigmented layer, the water line and the white line.
The coronet band at the top of the hoof wall actually grows this pigmented (colored) layer of horn that makes up the outer wall of the hoof. Although this layer is for protection it does not like sustained contact with the ground, which can cause it to break and flake away.
The water line is built up by the coronet and by the wall's corium (the living tissue immediately beneath the walls). It is thicker than the pigmented layer and increases its thickness, as it gets further down and away from the coronet band. Unlike the pigmented layer, this one is much hardier and is very resistant to contact to the ground so it is for support and protection of the underside of the hoof.
The white line is the inner layer of the wall. It is softer and fibrous in structure. Its color is yellowish. You can see it, in the underside of the healthy hoof, as a thin line, joining the sole and the walls. Since the white line is softer than both the walls and the sole, it wears fast where it appears on the surface and it appears as a subtle groove between the sole and the walls, with some debris or sand inside.
The three layers of the wall merge in a single mass and they grow downwards together. If the wall doesn't wear naturally, from sufficient movement on rough ground, then it will over-grow, much like a toenail that is not filed down and it then becomes prone to breakage. This means that a healthy hoof will self-trim, by breaking or chipping off. When a horseshoe is applied, it is fixed to the wall. The nails that are used to hold the shoe in place are hammered in at an angle so that the points come out of the front of the hoof wall.
The frog is a triangular structure clearly visible if you look at the underside of the hoof- it’s like the human fingertip. It extends forwards across about two-thirds of the sole. Its thickness grows from the front to the back and, at the back; it merges with the heel periople. Down its middle, it has a groove, the central groove (sulcus) that extends up between the bulbs.
It is dark gray-blackish in color and of a rubbery consistency, which makes it great to act as a shock absorber and grip tool, on hard, smooth ground. In the stabled horse, it doesn't wear but it degrades with bacterial and fungal activity to an irregular, soft, slashed surface. In the free-roaming horse, it hardens into a callous consistency, with a near-smooth surface.
The sole has a whitish-yellowish, sometimes grayish color. It covers the whole space from the perimeter of the wall to the bars and the frog, on the underside of the hoof. Its deep layer has a compact, waxy character and is called the 'live’ sole. Its surface will vary according to the type of ground the horse spends his time on. If there is no contact, as in shod hooves or when the walls are too long or the movement poor, the lower surface of the sole has a crumbly consistency and it is easily abraded (scratched off) it with a hoof pick. However, it has a very hard consistency, with a smooth, bright surface, when there is a consistent, active contact with the ground. The front portion, beneath the front of the pedal bone, is called the 'sole callus'.
They are inward folds of the wall, starting from the heels at an abrupt angle. The strong structure built up by the extremity of the heel and of the bar is named the 'heel buttress'. The sole between the heel walls and the bars is called the 'seat of corn' and it is a very important landmark used by natural hoof trimmers to evaluate the correct heel height. The bars have a three-layer structure, just like the walls. When overgrown, they bend outwards and cover the lower surface of the sole.
You’ll recall this is found at the top of the hoof and is responsible for creating the horn that makes up the hoof wall.
This is the outer layer of the hoof that forms a protective covering on the hoof wall. It is responsible for regulating moisture content in the horn, secreted from the perioplic ring above the coronet.
This is found underneath the pedal bone, within the insensitive sole. It produces the new cells that replace lost layers of the insensitive sole.
The digital cushion is found between the pedal bone and deep flexor tendon. An elastic, fibrous pad absorbs concussion from ground impact. It also helps to push blood back up the leg.
These are attached to the pedal bone and serve to protect the coffin joint. They also help absorb concussion.
The insensitive laminae are supportive structures that attach to the hoof wall and interlock with the sensitive laminae. The sensitive laminae then attach and support the pedal bone. The divide between sensitive and insensitive laminae can been seen as a white line on the sole of the foot.
This is term for the basic shape and size for a hoof and how fit it is for its purpose. It’s extremely important, as the feet are obviously essential to the horse
They should be even and round in shape and in proportion with the rest of the horse. The fronts should be of equal size and shape and so should the hinds.
The front feet should slope forwards and be at a 45 degree angle to the ground, and on through the fetlock and pastern. The hind feet should be at an angle of 50-55 degrees to the ground. The hoof wall should be smooth and free from cracks. Any lines could indicate poor nutrition or past cases of laminitis.
Poor conformation in the feet can result in strains to tendons and ligaments, tripping and bruising. Many such problems can be improved by a good farrier and over a period of time.
In respect of horse's health, prevention is the best cure. If you are regularly checking your horse to see that he’s in tip top condition then at least you will know that any accident has not been caused or worsened by an existing health issue.
Roger Bourdon has written a number of books dedicated to horseback riding, horses and the health of horses. His site www.anyhorsebackriding.com is dedicated to lovers of horses. It contains plenty of free information in newsletters, articles and contains loads of resources all about horses. Products such as books and DVD's are also available for purchase
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