How much should feed 800 pound horse have?

Answer 1

A horse that weighs 360 lbs give or take, would be a pony or mini. They usually don't require nearly the feed that a larger horse would need. A small flake of oat or grass hay 2 a day would probably be plenty for a horse this size.

Answer 2

All horses should have 24/7 access to good quality grass hay or grass, because if they go for extended periods of time with an empty stomach, it increases the risk of gastric ulcers, but more detail on that is for another question.

Most horses will be fine on just that. However, if he needs supplements you might mix the supplements in a small amount of grain to make it more appetizing.

And the horses that are worked hard need an extra boost of energy, and this can be given through alfalfa (but don't feed to much alfalfa, as in excess it causes stones in the digestive tract, and these are life threatening and require surgery to remove) and also special mixtures of grain.

So, the feed depends on much more than just weight. I advise you hire someone specializing in horse diets to plan one out according to your horse's needs.