The
purpose of our wild horse study was to see if there were hoof wear
patterns that were consistent, unlike many domestic horses that have a
wide range of hoof shapes and wear patterns. Arrangements were made
with the BLM to examine wild horse feet once these horses were in
lateral recumbency. We found each foot packed with dirt in the caudal
region of the foot, around the frog and bars. The distance from the
frog apex to the wall at the toe was always shorter than what we
commonly see with domestic feet that are shod. It is common for
domestic hooves to have a wide range of distances from the frog apex to
the edge of the wall at the toe. The frog of domestic horses often
becomes distorted and stretched forward as well. The bars on wild horse
feet all terminated about ¾” caudal to the frog apex. The heels
were worn back to the frog buttress in one group of horses that lived
in a shale, granite and sandstone environment. Others who lived in
softer, less abrasive terrain had longer heels that would press into
the sand instead of being worn away, very much like domestic horses in
similar environments. All horses had a small enlargement of frog at the
buttress and apex that was calloused, showing signs of weight bearing,
again very much like what we see on domestic horses.
When the dirt was removed, a flat
board was freshly spray painted and rubbed over the bottom of the foot.
The high points on the groundside of the foot received the fresh paint.
There were 4 primary contact points seen on every foot, two at the
medial/lateral toe quarters and one on each heel. A line was drawn
across the foot at the cranial edge of the black marks at the toe
quarters. Lines were also drawn from the toe quarter marks to the
diagonal heel marks. (Above Figure) The purpose for the line across the
toe was to identify where breakover occurred. Measurements were taken
from the apex of the frog to that line. A distance of 1” to 1 ½”
was recorded from the smallest to the largest feet (sizes ranging from
‘00’ to ‘2’). A closer look at the photographs and slides revealed that
the line across the foot at the toe passed through the back edge of the
sole ridge or callus. The lines drawn diagonally across the foot from
toe mark to heel mark intersected just behind the frog apex from
¾” to 1”(small to large feet respectively). A closer review of
photographs and slides also clearly showed this intersection marked the
widest part of the foot. Traditionally many authors agree that the
widest part of the foot always maintains its relationship with the
distal phalanx, even when the sole at the toe migrates forward, and the
heels become under run and change their relationship to the widest part
of the foot. This static feature of the foot helps us to see the distal
phalanx (P-3) more clearly and enables us to see hoof deformities long
before they become a problem. The self-maintaining feet of horses in
the wild as well as domestic self-maintaining feet, all have the same
basic surface pattern when viewed from the bottom of their foot. To
establish a guideline for measuring, a line is drawn across the foot at
the widest part. Another line is drawn across the toe at the leading
edge of the imprint marks. A final line is drawn to identify the most
caudal part of the frog. This line will fall just behind the bulbs of
the frog at the caudal aspect of the central sulcus. All
self-maintaining horse’s feet measure a greater distance behind the
centerline at the widest part of the foot to the caudal frog, than
forward to the point of breakover. Ground surface mass is described as
the area of the foot that is on the ground, behind the line identifying
the breakover point and ahead of the line identifying full caudal
support of the foot. Routinely, in wild horse feet the ratio was 1/3
foot mass cranial to the widest part of the foot, and 2/3 caudal to the
widest part of the foot. (Above Figure) The dorsal hoof wall had no
deviation from the hairline to the ground, unlike many domestic feet.
In domestic horses, the dorsal hoof wall at the hairline is often more
upright or vertical than the lower half, which is an early sign of hoof
deformity. |
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