Blimey, I can't withdraw romaine from my boys - I'd have a piggy mutiny on my hands! They love it - when they've been poorly its the only thing they will eat along with grass and dandy leaves.
Ours have celery, carrot, cucumber, sometimes apple, tomato and romaine most days - but only a bit of each. Occasionally they get kale, cabbage or spinach. We also pick dandy leaves sometimes for a treat or if they are off their food.