I think you'll find bank barns are a German tradition.  There is a track that runs the length of the barn with a car on the track that carries a rope hoist with a hay hook on one end.  Back your wagon of hay up the bridge, unhook one horse and hitch him to the hay hoist.  Set the hooks in the hay and send the horse forward.  When the load of hay reaches the top it will trip a release on the car, allowing it to roll to the end of the barn (the track is on a slight angle).  When the hay is over the mow, release the hooks, pull the car back over the wagon and do it again.  Easterners don't have the luxury of storing hay outside, especially loose hay.  You will never see a beaverslide East of the Mississippi.