A PAPER WRITTEN BY PENZANCE student on
"Balanced Hoof Loading"
March 31, 2008, Week 2
Balanced Hoof Loading
The mechanics of balanced hoof loading
are a complex yet highly efficient series of events that serve to
absorb the shock and concussion of the hoof striking the ground,
facilitate the instantaneous distribution of weight and dispersion of
force, and supplement the work of the heart in the circulation of the
lower limb. This efficiency of function is important, in that all
life forms must conserve energy as much as possible while still
performing the functions of living. To have the optimum performance
in the hoof allows the horse to travel to food and water sites, and
to escape predators, while expending the least amount of energy.
The hoof is loaded first from the heel
area, through the bottom of the hoof, to the breakover at the toe,
where the hoof leaves the ground. Several things happen in this very
brief sequence, which, when the structures are in balance, allow for
the proper performance of the hoof mechanism.
First, as the heels press against the
ground, the frog spreads down and to the sides, pushing out the rear
sides of the hoof wall and allowing the lateral cartilages to bend.
This expansion of the rigid wall causes a slight contraction of the
upper portion of the hoof wall, at the back of the coronet. The
spread of the hoof walls also causes the sole to flatten down towards
the ground, leaving a “space” that brings arterial blood into the
coria of the digital cushion, the lamina and the blood vessel
networks on both sides (axial and abaxial) of the lateral cartilages.
[Jaime Jackson, Horse Owner’s Guide to Natural Hoof Care,
Chapter 3; C.C. Pollitt, “Clinical Anatomy and Physiology of the
Normal Equine Foot”] As the horse’s body is propelled forward,
the support tendons in the heel of the foot start to pull upward.
This tensioning of the tendons unloads the digital cushion, as the
wave of expansion flows forward. [Jaime Jackson, Horse Owner’s
Guide to Natural Hoof Care, Chapter 3]
As the loading forces continue to roll
forward, the blood in the sole corium and digital cushion is squeezed
out as the heel begins to re-contract. There are many routes for
this venous drainage via small branchings in and around the internal
soft structures. The lack of valves in these branchings, and the
valves in the larger digital veins allows the pressure to be evenly
distributed, facilitates the return of venous blood to the heart, and
permits the dissipation of the heat energy created. [C.C. Pollitt,
“Clinical Anatomy and Physiology of the Normal Equine Foot”]
By this time the hoof walls have made
ground contact, and the concussive forces there are dispersed by the
lamina that transfer this force to the hard coffin bone. [C.C.
Pollitt, “Clinical Anatomy and Physiology of the Normal Equine
Foot”] The hoof wall, being more dense with a lower water content
on the outside and less dense with a higher water content on the
inside, is able to allow for a smooth energy transfer and to dampen
some of the forces on it. [C.C. Pollitt, “Chapter 2, The Horse’s
Foot” Equine Laminitis in Australia] By the time breakover
is achieved, the re-arched sole and the re-contracted hoof walls have
pressed out the remaining additional blood flow, and the hoof, frog
and heels have returned to their resting, unloaded state. [Jaime
Jackson, Horse Owner’s Guide to Natural Hoof Care]
While complex in the telling, the
action of the hoof mechanism is elegant in its execution, and truly a
marvel of nature’s efficient engineering.