With any 'tummy bunnies' Avoid any of the brassicas and try not to feed too much sweet stuff like carrots.
Wild herbs such as brambles, hogweed, shepherds purse etc etc are generally very good for them and buns love them!
If you have one prone to stasis then next Autumn pick and dry blackthorn shoots. They are only effective as a remedy it seems in the 6 weeks before leaf fall, but they do work wonders and dry very very well