Blueseyes, some horses, like people, do lose weight with old age. At 27 my gelding began to lose weight, just a little but noticeable. His diet was altered in my attempts to get his weight back up. He'd gain some then lose it. He wintered well but continued the gradual weight loss. It didn't matter what he ate, the weight wouldn't go back on. One has to realize the organs aren't functioning as they should. That fall, he was thin and there was no way I wanted him to try to endure our very cold winters so he was put down.