Actually, the pictures do not really show his true weight. He was really bad when I got him. His butt has filled out ALOT. Since he has white, it like a trick to the eye. I can tell and feel that he has put on a lot of weight in short amount of time. I know what your saying about being thin and not getting them too fat. I rescued an overly obese horse that had suffered from laminitis in the past also but that had been several years ago.
Oops, I feed alfalfa but only as like a treat. I have round rolls of grass hay, nothing special, just grass. But I spread out like 6 piles of alfalfa hay, which has really helped him put on weight. Not 6 flakes, I get about 3 flakes and make 6 piles out of it so they have to "search" for there food to simulate roaming free and to help them move around and walk in there pasture since pasture horses do not walk near as much as there wild counterparts, it encourages them to search and walk to help with digestion and to keep them from being bored.
I also feed him Senior feed which is a complete feed and its pelleted.
Deerly, my farrier pointed out by the bottom of his feet, where it has come down and said that is typical founder and from the long toes. My farrier has shod/trimmed foundered horses before, even a severe case. Usually with founder the toes grow longer I think. No x-rays were taken to fully comfirm, previous owner said he did founder from the owner before him. Not sure which owner really did because I know for a fact this guy was ridden HARD on the roads pounding away. I think he road foundered possibly. Stress from constantly pounding the pavement. He had shoes when I got him and my farrier wants to trim him up and keep him barefoot for a while and see what that does. He limped bad or "walked on eggshells" bad with shoes on and I do not see that while he is barefoot. If after several months barefoot isnt working, we will try shoes.
I also have him on Biotin supplement too and a joint suppliment.