Healthy Hoof
A healthy hoof is basically a hoof that is in an
equilibrium, doesn't deteriorate and allows the horse to stand
in relaxed position and run troublefree. As everything in nature,
the shape and angles of hooves vary. There are however some rules,
that depend on general physics.
Design of the Hoof Capsule
The hoof capsule made of keratin like a fingernail,
its horn is formed by the cells of the corium. Below you see the
hoof capsule taken off a dead hoof, with the corium exposed.
The corium is about 3 mm thick, surrounds the coffin
bone, lateral cartilage and digital cushion and
consists of different
areas that form horn with different properties:
1) the coronet forms the hard horn of the
hoof wall, it grows downward
2) the lamellar corium forms softer "cement horn" that attaches
the hoof wall to the corium,
so the hoof wall
can grow down like on
rails
3) the sole corium forms the softer
sole horn, which is around 8-15 mm thick. In a healthy hoof,
it starts crumbling by itself at a certain thickness, builds a
tougher upper layer (callous) when
exposed to pressure and shows
the same shape as the bottom side of the coffin bone
4) the frog corium forms the rubber-like frog horn. Look at its
shape, this is about how a healthy
frog
should look like
The corium has a very high metabolic activity, is
very vascular with fine capillaries, and contains nerves.
If the
hoof capsule puts too high pressure or stress onto
the corium, e.g. because it deforms in an unphysiologic way, this
causes -> pain. The
horse tries to avoid the pain by changing its stance or walking
"crookedly".
When the lamellar corium becomes inflamed -
this may happen due to different reasons - it causes a highly
painful swelling. This is called -> founder.
It may lead to a separation of the hoof wall from the lamellar
corium.
Optimum Shape of the Hoof Capsule
1) Straight (or plane) coronet
2) Straight hoof walls when seen from the coronet down, no flaring
3) Direction of growth almost
perpendicular to hairline
4) Coronet-toe angle: ~ 95° in hind hooves or
~ 105° in front hooves
5) ~ 30° hairline to ground, this
angle may show natural variation (+)
6) Outline of the hoof print (hoof wall) should be symmetric to the outline of
the
sole
Ground Parallel Coffin Bone
The coffin bone is well connected to the tough coronary
band. Thus, when looking at the coronet,
we can estimate the position
of the coffin bone inside of the hoof capsule. The toe wall may
be
separated from the coffin bone and cannot be taken as a reference.
With
a 30° hairline angle, the coffin bone is close to ground parallel.
Out of a physical
view,
this
would
be
the optimum
angle
for load distribution. The hoof is however no static building,
it deforms
with load. This deformation is called hoof mechanism
and must be taken into account.
The sole and bars form a natural arch under the hoof
(-> Article
by KC LaPierre). It is like a spring,
it's strength depends
on the amount of structure in the hoof. A wild horse that has grown
up on
hard ground
would develop
a thicker sole and a stronger and higher arch, than the same horse
living on soft ground. This would
develop a rather
thin sole and flat arch.
This natural, functioning arch, that shares in weightbearing, is
expanding in axial and lateral direction
upon loading of the hoof
and does
thus not
collide
with internal structures. It must not be mixed up
with unhealthy
and non-functioning structures like
the arch formed by sole contraction in the chapter
->
navicular.
The principle found by KC LaPierre (HPT
method) is:
Structure + Function = Performance
Explanation with some interpretation
by myself:
-> a hoof needs good, healthy, elastic structure,
that is able to
resist
the demand
(shock
and
stress) without taking
harm or being destroyed
-> the strength of the structure must not be too high, function
must still be possible in the given environment and with the
given demand
-> the structure must be in the right place, so that a physiologic
hoof mechanism (function) is possible
-> function is not only the "classic hoof mechanism" (expansion
of the hoof walls), but includes
every distortion of the hoof capsule,
like
torsion, local shifting of horn tubules, pressure on sole,
in general: everything that changes the volume of the corium.
-> structure can be built by training, that means exposure to
stimulation, which of course must not
exceed the weightbearing (elastic)
limits of the current structure
-> a horseshoe adds artificial structure to the hoof, but also
decreases its exposure to stimulation
which leads to weakening inner structure.
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