Internal Foot Anatomy of Feral and Domestic Horses
Dr. Bowker presented numerous slides, including cellular level sectional views, which compared feral and domestic horses' feet.
Presented by Dr. Bowker
It appeared that genetic basis was not a significant part of his findings. While specimens predisposed to week foot structures probably did not flourish and propagate in the wild, it was my conclusion from Dr. Bowker's presentation that the feral horses sampled would not have clinically been any different from a a viable band of decently bred Arabian horses which were set free to adapt to similar terrain and survive on their own. Thus the findings of feral horse feet could be applied to improving the care and maintenance of feet in domestic horses.
The hoof wall structures of domestic horses could be expected, within reasonable limits, to respond similarly to environmental conditions as did the hoof walls of feral horses. The sensitive laminae do have the ability to divide cells and make some "repairs" (for lack of a better term) to damage that has occurred in the laminar bonding of the hoof capsule. While it would take on average one year of growth for new hoof wall to grow from the coronary band to the sole, some damaged areas appeared to undergo some partial reattachment through the proliferation of secondary laminae.
The density of laminae of both feral and decently endowed domestic feet is equal at birth. With proper exercise, the laminae of the foal at four weeks become more dense at the toe, in the orientation of between 10:00 and 2:00 if a clock were superimposed over the foot.
The density of the laminae in 60% of older horses examined was more dense on the medial side, and 40% had greater density on the lateral side. 100% had greater density on the forelimbs. The apparent conclusion is that laminar density response correlates to, and is in direct relation to, pressure or weight bearing.
The elastic tissues of the hoof are effected by high levels of steroids (e.g., dietary caused founder) which result in damage to the laminae. In cases of chronic laminitis, the sensitive laminae take on the appearance of "flames" and the secondary laminae disappear.
The buttress of the frog contained a high concentration of proprioceptors. Thus the frog was instrumental in sensing the terrain, which could explain why the buttress of the frog is so quick to try to regrow when trimmed back during hoof maintenance. In the feral horse, the frog touches down first providing some sensory perception of the ground.
In instances where the coronary band and the extensor processes of the coffin bone were aligned, the horses appeared to be more sound. In feral horses these structures were consistently more or less aligned. In many domestics, the extensor process is lower than the coronary band. As a viewer of the lecture, I took this to mean that hoof wall contact with the ground or shoe actually forces an elevation of the coronary band (the wall can't grow down so it has to push the band up) which had a modest detrimental impact on soundness.
P3 actually moved within the hoof. This finding was based on radiographs of horses standing on various surfaces. When the sole of the hoof was not supported (e.g., not standing on a softer surface which would fill and support the sole cavity), P3 actually sank inside the hoof structure. This finding would better explain the dynamics of road founder and why feral horses with mud caked feet, traveling over extremely hard terrain, did not suffer from similar laminitic conditions that appeared in domestic horses that were engaged in similar levels of exercise over hard surfaces and suffered from signs of laminitis.
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