This may seem weird, but I have one at home that’s had a long-term issue with thin soles and my farrier and I have determined he started growing and keeping more sole when I put him on ranitidine (OTC ulcer medicine, aka “Zantac”) twice a day. He is not getting what would normally be a “therapeutic dose” (twenty 75mg tablets TID), but the dose I have him on (15 tablets BID) seems to be enough to maintain his tummy and help him grow sole. He is also not allowed any significant amount of grass, which seems just plain wrong, but works for him. He gets about 4 pounds of soaked Kent Dynasty Secure, divided into 2 feeds, along with his ranitidine and a twice daily dose of TractGard. My farrier saw a difference in a single trim cycle, so might be worth a try, especially if your horse has any history of ulcers, low level colic or other tummy symptoms. Of course, check with your vet to see if there might be any contraindications in your horse’s case.