No wonder the wild horse wears his heels short. Long heels prevent the frog from making any contact with the ground. The hoof cannot expand and contract. The coffin bone is tilted upright, driving its point downwards through the hoof. And the heels can grow forwards, becoming under-run.
Without the ability to self-trim, the domestic horse relieves pain by shifting to a toe first landing. This feeds the vicious cycle, moving him closer to lameness.
With the heels, sole growth will once again tell you how far to trim. This time, look to the hoof’s seat of corn. Scrape away any dead sole, and see how far the heels stand above these points. These two points mark the level that the heels should be brought to.
Rasp down the heel bulbs, and bars to the level of the seat of corn. Take care not to go below the hoof’s live sole level.
When you’ve done this, lay your rasp across the heels. Your aim is for a heel-landing platform that includes the heel bulbs, the frog and the rear of the bars. The heel bulbs should be even, making equal contact with the ground.
It’s unlikely you’ll achieve all this with one trim. You must rely on barefoot movement to work with you. In time, the heels will de-contract, soreness will disappear, and they’ll begin to lower themselves. Keep reading the soles at the seat of corn, and trim to their direction.