I bought some hay at a local farm about a month ago. It was not moldy when I got it. I filled three plastic tubs and one yard bag with it. One tub I kept in the house and the others I kept in the garage. They were in a dark, dry place. My rabbit does not care for the hay so I was going to donate the hay in the garage to the shelter. When I opened the bag and the tubs the hay was damp and moldy, ewww! I checked the hay in the house, but it isn't moldy at all. Why did the hay in the garage get moldy, and how can I prevent it in the future?