We have one. Luckily he is an easy keeper. He gets a senior feed with lots of BEEP in it and does ok. He eats a fairly large volume but grazes slowly during the day. During the cold months he’s a bit thinner but he plumps right up when the grass comes in. He has a licky block to keep him busy when he’s in the stall. He’s had several surgical colics and a colitis episode and he simply can not tolerate even a small amount of chopped forage or pellets. He has to be totally hay free.
If you can feed beep and really high fat grain, multiple times a day, hopefully you’ll have an even easier time.