Wow, its amazing how expensive it is for shoes these days. I ride at a farm where no horse has a shoe, boot, or polo on, ever. When I'd moved to this farm I'd asked the question of- WHY? It seemed so strange and my new trainer simply told me "What did they wear in the wild?" If a horse is over stepping, or one toe is short its what connects the foot to the horse that's at fault. Or in your case its the intake of what vitamins your horse is getting. I've always had bad nails until I started taking iron, iodine, and selenium. Now their almost unbreakable and I no longer have bumps in my nails and they grow more. Think of your horse's hooves as nails and you'll understand more. A horse supplement that I use for my horses is called Red-Cell and it has an amazing amount of vitamins that our horses love, retired and performance.