I hate to say this but, Nutrena Safe Choice Senior has worked the best of anything to put weight back on my 27+ Arab.
The reason I hate to say that is because Nutrena's forumulas are not fixed and I don't like that.
I tried Triple Crown Senior over the summer and he kept losing weight. I have to drive 40 miles to buy Triple Crown, so I bought extra. I kept it in the house and I still ended up throwing out a whole bag because it went bad
I drive 12 mile to Tractor Supply and buy the Safe Choice Senior which, for reasons I don't understand, works better than Triple Crown.
My Arab has had two physicals within six months, a full CBC, insulin and cortisol checked, fecal checked, a thorough vet-hands-on checking for tumors and the conclusion was Streeter is healthier than I am
The amount of food his 13.3H self consumes in a month would literally founder a Clydesdale. He was already eating more than my three TWH's combined, when the vets at the facility conferred and concluded I need to feed him more
If this is metabolism-driven, I want to trade with him