Originally Posted by RebeccaMI
My boy will be 21 in June. He's an Appendix QH so his TB half gives him the tendency to be ribby. Rather than senior feed, I've got him on a ration balancer made by Buckeye called Gro N' Win. It's designed to be fed along with forage (either hay or pasture). Because it's a ration balancer you feed less of it per day than you would senior feed, which may be nice for your senior horse if s/he has trouble chewing. (I've not needed to do this, but I'm sure you could make a mash of it with warm water.) In addition to the ration balancer and hay/pasture, in the winter he also gets a pound or two of whole oats daily for weight management. He's pretty much dialed in on this combination and stays a good weight.
I've not used it, but some people use a product called Cocasoya to add weight. I've also read that some people feed black oil sunflower seeds (BOSS) but that can get expensive, and it might be harder for your horse to eat those with fewer teeth.
I would not recommend BOSS for an older horse b/c it is very high in omega 6, which is an inflammatory. Plus, you can only feed 2 lbs max.
Cocasoya has one of the better Omega balances for an oil. I have used it with good results.
I would go with a RB and alfalfa pellets and/or beet pulp, all soaked if he has trouble chewing. He can be fed up to 5+lbs of BP/AP along with his RB if needed.