If you have an overweight horse I would say cut off some grain or switch to a vitamin supplement type thing, but you can't just not give your horse any hay/grass - they need one or the other. With horses that are overweight due to insulin resistentance (or any other metabolic problem), you're supposed to have them in a dry lot and soak their hay.
With skinny horses, I say give them 24/7 hay and slowly add grain until you get them up to an everyday ration.
It totally depends on horses, freechoice hay makes a skinny horse get to a decent weight (usually, unless they are a hard keeper) and other horses maintain their weight, I don't think it makes horses overweight. I think grain plays more of a role in that.
passion is when you put more energy into something than is required to do it. it is more than just enthusiasm or excitement, passion is ambition that is materialized into action to put as much heart, mind, body and soul into something as is possible. // <3 starlite - dream - lady - georgia