I used to feed my hard keeper a flake of straight alf. Per feeding. It didnt make him hot one bit.
Its like saying you car will always go faster, just because it has more gas in it. It really depends how hard you push the petal
A horse with alot of excess energy-from food, will usually be a little hotter to try to burn it off. If a person skip meals, its sort of the opposite reaction. Over feeding any horse can lead to hyperness. I think you have to look at the whole feed plan, not just the alf. They are given. My horses eat grass 24/7 in the summer, which is very green and has lots of protein. They arent one bit hotter for it. They even get about a scoop of alf. Pellets once a day, with no adverse effects.