The mechanical forces of the 60:40 and 70:30 ratios Bowker sees put pressure on the coffin joint, which eventually leads to navicular disease, he explained (see #5 in the sidebar). Everyone knows this and understands some of the biomechanical issues with this type of foot, but few try to aggressively correct the problem, he told The Horse. Many foot professionals say that such feet are not correctable, or they are only manageable. With this long toe-underrun heel foot, the already-long toe continues to get longer. I mean the actual coffin bone begins to get longer: Its conformation is gradually changing.

As the coffin bone gets longer, the vasculature beneath it must change at the expense of the back part of the foot and the frog; basically, the expanded toe area demands more of the foots blood supply, routing it away from the back of the hoof, which he said is detrimental for the hoof and its overall long-term health.

Of all these husbandry practices, the long-toe, underrun heel is probably the worst one that will give rise to navicular and will definitely make any bout of laminitis much worse, Bowker told The Horse. With a long-toe, underrun heel, the tissues supporting and surrounding the coffin bone become compromised and the distal (bottom) end of the coffin bone gets less and less support and becomes thinner and thinner along the edges, especially the lateral (away from the midline) side of the foot. These changes will often result in pedal osteitis; many people have heard of this problem.

When theres a bout of laminitis (and added) toe pressure through some rotation at the toe, the bone cannot support the weight of the horse with this peripheral thinning of the bone, and the coffin bone becomes crushed, he added. Thats the end of the horse!

We are setting the horse up for failure by having a long toe with our trimming methods, regardless of whether the horse is shod or barefoot, he said.

Bowker trims to shorten the toe and promote caudal (toward the rear) migration of the heels to bring the central sulcus (the cleft between the heels) back to the sole of the foot so it makes light contact with the ground. He said trimming with these goals can improve the foots health and get the ratio to approach 40:60allowing the back part of the foot to enlarge and return to its robust health.

Our (industry standard) trimming is such that very few people trim inside the white line, he said, and not only does the hoof wall get longer, the coffin bone gets longerthis remodeling changes the conformation of the bone and its bone density. My belief is that we can correct that, but its going to take time and effort.

See the original post here:
Hoof Trimming to Improve Structure and Function - TheHorse.com