Thanks to all who replied.
Please note that I was asking about feed, not for evaluating his happiness with life, when to put him down, or responsibilities of previous owner. I made a decision to "rescue" him. He is still enjoying life. I'm sure I can't and won't even try to use him, but I enjoy him and his teammate and as long as they seem to be enjoying life, I'm gonna try to allow that to happen. I have a good team of drafts, and I enjoy drafts. These boys, Duke and Dan are a couple of good looking boys just to be around.
FYI, I have little severe winter weather (I'm in south Texas), lots of spring, summer and fall grass, and I plant oats each fall which is winter grazing for the horses. They also have lots of trees for shade and windbreak. They also have free access to a "tank" (a pond for y'all Yankees), plus a water trough. All my horses are also fed a small amount of grain morning and night, primarily so that I can check on their health twice a day.
FYI for now I've decided to geed Purina EQ SR, as it is readily available. Thanks again for the responses. kelly