Chris, run this past your vet first, but my neighbor also has a
22-year-old mare that is a chronic founder. The vet put her onto grass
(bermuda) hay and no alfalfa at all, but she can't maintain weight on
bermuda alone and any sort of grain started her foot problems again.
She wouldn't touch corn oil in any way, shape or form. I suggested beet
pulp to Teresa, her vet said okay and she's done well on it---no more
foundering,she's maintaining weight better and her overall health seems
improved (beet pulp really does have a pretty nifty nutrient profile to
it).
I'd say it might be a good alternative for him, but again, please check
with your vet first.
Good luck,
Susan Garlinghouse