Cages should be designed and maintained so as to avoid injury to birds. Construction of cages, feeders, and waterers should take into account scientifically documented advantages for bird comfort and health, and facilitate the safe removal of birds. Cage configuration should be such that manure from birds in upper level cages does not drop directly on birds in lower level cages. All hens should be able to stand comfortably upright in their cages. Feeder space should be sufficient to permit all birds to eat at the same time.