So I feed kinda your base diet of alfalfa pellets + oats to my whole little herd. Amount of pellets and inclusion/amount of oats varies depending on what each horse needs. I add a few things like Vermont Blend Pro and flax and vitamin e.
Oats range to nothing (for the fatty) to close to 3 quarts. I use hulless oats, so they’re heavier by volume than regular oats.
Never saw an energy increase in anyone.
Obvs there’s a huge ymmv element because some horses are more sensitive to NSC than others. Mine have never gotten up or snorty, and NSC of their buckets with the oats + pellets was somewhere in the mid to high teens, which they’ve always tolerated without issue before, so I didn’t really expect a change.
But unless this guy has shown you he’s sensitive to NSC or oats in particular in the past, I wouldn’t necessarily expect much. It’s certainly something to try, but definitely not a sure thing.