left outside. The wrap repels moisture but leaves the ends of the bale exposed so that the hay itself can "breathe" and does not begin to ferment. When it is possible to store round bales under a shed, they last longer and less hay is lost to rot and moisture. Haylage For animals that eat silage, a bale wrapper may be used to seal a round bale completely and trigger the fermentation process. It is a technique used as a money-saving process by producers who do not have access to a superior silo, and for producing silage that is transported to other locations. In very damp climates, it is a legitimate alternative to drying hay completely and when processed properly, the natural fermentation process prevents mold and rot. Round bale silage is also sometimes called "haylage", and is seen more commonly in Europe than in either the United States or Australia. Hay stored in this fashion must remain completely sealed in plastic, as any holes or tears will allow the entrance of oxygen and can stop the preservation properties of fermentation and lead to spoilage. Stacks Haystacks are stacks of harvested hay, stacked in many different ways depending on the region of the world, climate, if baled or loose, and so on. Hay requires protection from the weather, and is optimally stored inside buildings, but weather protection is also provided in other ways involving outdoor storage, either in haystacks or in large tight bales (round or rectangular); these methods all depend on the surface of an outdoor mass of hay (stack or bale) taking the hit of the weather and thereby preserving the main body of hay underneath. Traditionally, outdoor hay storage was done with haystacks of loose hay, where most of the hay was sufficiently preserved to last through the winter, and the top surface of the stack (being weathered) was consigned to become compost the next summer. The term "loose" means not pressed or baled but does not necessarily mean a light, fluffy lay of randomly oriented stems. Especially in wet climates, such as those of Britain, the degree of shedding of rainwater by the stack's outer surface is an important factor, and the stacking of loose hay was developed into a skilled-labor task that in its more advanced forms even involved thatching the top. In many stacking methods (with or without thatched tops), stems were oriented in