Big enough to let them have a canter around. Only thing that bothers me is that they have no grass! They have constant access to good quality haylage and frequent treats of carrots etc. And loads of love and attention. They SEEM fine and not unhappy, but one or two people have commented that it's cruel to keep them without grass. Is this so? Occasionally they have access to a small area of grass when it grows long enough, but not that often. Would appreciate your thoughts on this.