yea id get a treat ball my mare loves it, you could also try and get a likkit holder that you can hang from the celing and place it somewhere where he cannot pin it against the wall and it should keep him busy for hours.

also a mirror might be helpful try www.likit.co.uk these gave me some good ideas

hang a couple of swedes!! keeps my haffy going all night!!

You can go out and buy things such as ...

Balls that they can move and treats come out of them.

Salt licks, Lick its. Sweet things.

Things that hang on the walls and move.

You can do things yourself though. Such as getting a 2 litre bottle and filling it with water and hanging it in the stable somewhere, Hanging the haynet up somewhere high. Buying lickits and hanging them as its harder for them to get to. This gives them a challege because they have to work for something they want.

Hope this helps :)