When it comes to hoof balance, most farriers rely on “feel” over facts. “Looking down the leg” and inspecting worn shoes may be tried methods, but they’re hardly scientific. About the only certainty is a horse out of balance is usually a horse with foot problems.
Well, now science has arrived on the scene.
The Hoof Project, the ongoing research of the equine foot headed by Texas A&M University equine veterinarian David M. Hood, has launched a lengthy study of how normal and malformed horses’ feet are loaded when standing still and on the move. Hood presented the study’s preliminary findings to farriers at the 1999 American Farrier’s Association Convention last March in Lexington, Ky.
The “Balance” Study
The study evaluated three factors: the effect of ground surface, basic foot conformation and the effect shoes have on the loading surface. Each is measured using a pressure-sensitive mat placed between the ground and the bearing surface of the foot in order to determine the contact and pressure points of a horse when standing and at various gaits.
Hard Vs. Soft Ground
Obviously, the environment a horse lives in dramatically affects how forces are applied across the foot’s solar surface. The study determined that horses standing on flat, solid ground place force largely on the hoof wall.
“The uniformity of the contact between the wall and ground depends on how even the wall has been worn by ground contact or how it has been trimmed,” Hood says.
Conversely, a horse standing on a soft surface places force mainly on the sole and frog, with the wall picking up some of the load.
The study has already shed new light on hoof problems suffered by unshod horses kept on soft ground. Previous studies indicated the four-point pattern commonly seen in pasture horses is caused when the hoof wall wears down across the toe and quarters.
“This study indicates the four-point loading pattern is the result of a lack of force applied to the ‘points’ rather than the points being the areas that are loaded on [soft] ground,” explains Hood.
Regardless of hard or soft ground, you should strive to maximize the area of the foot in contact with the ground.
“The increased contact area decreases the amount of pressure placed on any region of the foot which, in turn, serves to protect the foot,” Hood says. “Trimming methods should logically be designed to increase the surface area of contact.”
Standing Vs. Moving
Hood emphasizes farriers must remember that horses spend the vast majority of their time standing.
“Low-grade forces applied constantly can change the internal and external structure of the foot,” he says.
For example, when the horse is standing squarely on all four feet, forces are higher on the medial-fore quarter of the foot rather than being in the center. It is this uneven application of loads that are thought to result in the different angle of the medial wall relative to the lateral and the greater surface area of the joints on the medial side of the foot.”
Moving horses strain the hoof wall. Studies show most horses at a walk land heel to toe, meaning “the decreased area of the foot touching the ground at contact and breakover result in high pressures being applied to these regions. It is these relatively high pressures that put the hoof wall at risk of mechanical failure,” Hood explains.
Trimming, Extended Heels
Hood says that standard, non-four-point trimming causes the desired increase in foot surface contact, which disperses the pressure more evenly. While removing the hoof wall makes the foot smaller, Hood says, surface contact increases for three reasons:
1 Trimming brings more of the wall, bars, sole and frog into contact with the ground.
2 During trimming, those areas of the wall which have developed into points due to a lack of frictional wear are removed.
3 Trimming tends to lengthen the foot’s solar surface as the heels are lowered.
The study revealed that using egg bar, or extended heel shoes, affects lame horses differently than healthy horses. In healthy horses, extended heel shoes “tend not to move the loading toward the heels. The use of these shoes in horses with chronic laminitis, however, did shift a percentage of the load to the heels.”
Science And Sense
So far, much of what the Hoof Project’s latest study has turned up confirms what farriers already knew. This goes to show that scientific evidence and good old intuition aren’t necessarily enemies.
As the study progresses, new findings will lead farriers to continue old techniques—as well as try their hands at something new.