I have my horse, who is a coming 11 year old 17hh hard keeper, on Triple Crown Senior right now and he's doing very well! Being a hard keeper, it's been a challenge to keep weight on him.
Anyway the barn gives him 2 scoops per meal (I know it should be weighed.. but it's a busy barn) and he's keeping his weight on while I'm exercising him via lunging and riding.
Do you know his history, if he's allergic to anything?
If you're looking to gain weight, you want a high fat %, but make sure there are vitamins and nutrients in the feed. I'm not sure about the other two feeds. But I hope I've helped.
"Strength is the ability to use a muscle without tension"