I have a horse who is 37 years old (yes, 37!!). He gets around just fine for his age, but my problem is putting and keeping weight on him. We had the vet check him awhile back and she told me to get his feed ground as fine as possible, which I did. He is a very good eater, and it doesn't seem to just be passing through him. Any suggestions on how to get his weight up for winter would be greatly appreciated. Thanks.