He was probably euthanised because of recurrent abscesses. Patience, lowering the heels and backing up the toes could have saved him. In the worst case scenario, the entire hoof capsule actually sloughs off . Horses have survived this with proper holistic care and natural living conditions. This is certainly a more workable approach, where the floor is kept clean, than in a stall where the horse will be stepping into his own wastes.
New growth is rapid.
She uses apple cider vinegar soaks, and sometimes propulis tincture, not bandaging and disinfectant chemicals. The horse does not use the foot for some time, but a new hoof does grow back. I also had a farrier in Illinois, Don Tritz, who brought a horse back who had sloughed off two front hooves, just keeping pads taped on the stumps until the walls grew back down. The heels had to be trimmed often, though, as they grow in first. He tells me it took close to a year for a new hoof to grow down completely at the toe, but that the horse did recover.