Abstract: A feeder adapted to be positioned on a structure having a bed for supporting hay includes a plurality of walls adapted to vertically extend above the bed and including at least one opening through which hay upon the bed may be accessed by livestock. At least a portion of one wall is selectively movable between a first position in which the portion of the wall extends above the bed and a second position in which the portion of the wall extends below the bed. The feeder is preferably adapted to be carried by or built as part of self-driven vehicles and pushed or pulled vehicles, such as trucks and wagons, respectively.