To ellyelle, if your horse is stabled only and not turned out at all then yes you should be feeding something more than just hay and mineral licks.  You need to ensure a balanced diet with enough vitamins.  You could contact one of the feed companies for advice as what you feed will depend on the amount of work you do with your horse.  My cob at 4 years old when stabled was feed twice per day with 2 normal sized scoops of sugar beet pulp and a large round scoop of alfa a oil, with ad lib hay.  This is still what he has when stabled. 

My cob does exactly the same,but when he finishes his feed he then gives me the bucket to take away,if im not there then he throws his buckect over the door.

He's just happy and getting a lot of pleasure from his feed. Mine (also a cob!) does exactly the same thing.