How much work is he doing, is he underweight overweight or a good weight, is he fizzy or sluggish, are you a novice rider or very experienced? Do you think he needs energy / does he get tired easily? How big is he?

Depending on the answers to all these questions would depend on what you might feed. To start with I would always feed ad lib hay (unless really fat).

Oil is a good source of slow release energy without adding fizz, and a balancer will help supply essential vitamins, minerals and nuitrients.

A lot of feed companies will advise on a feeding reigeme (with their own feed obviously)

Let us know the answers to the questions if you can

I know its a lot to take in but I hope this helps