Round hay bales for goats?

I was thinking about getting a big round hay bale for the goats this winter. My concern is this: When I had my horses, I was always very picky about the hay, worried about it molding. How do those big bales keep from going bad? They are being left out in the weather,with no protection from the rain. I see them in the fields here for livestock and wonder if it would serve my goats better than square bales.

We have the equipment to haul the round bales, so that is not a problem.

Thanks!