Any reason I cannot use this as a collagen supplement?
Nope, go for it. I’ve given my horses the collagen supplements that I can’t stand, with no ill effects.
It might be spendy to hit a horse sized dose? But if you’ve looked around and this is the best choice from that perspective, no harm in using it.
From what I see, in most horse specific collagen-one scoop a day is actually MORE.