An HSUS Report: A Comparison of the Welfare of Hens in Battery Cages and Alternative Systems

Housing systems for egg-laying hens range from small, pasture-based flocks to large, commercial-scale operations that intensively confine tens of thousands of hens indoors. The overwhelming majority of laying hens used for commercial egg production in the United States are confined in battery cages and provided 432.3 cm 2 (67 in 2 ) of space per bird. Cages prevent hens from performing the bulk of their natural behavior, including nesting, perching, dustbathing, scratching, foraging, exercising, running, jumping, flying, stretching, wingflapping, and freely walking. Cages also lead to severe disuse osteoporosis due to lack of exercise. Alternative, cage-free systems allow hens to move freely through their environment and to engage in most of the behavior thwarted by battery-cage confinement. Given their complexity, cage-free systems can be more challenging to manage and may require superior husbandry skills and knowledge. Laying hens must be genetically suited to the alternative housing system to realize its full welfare advantages. Regardless of how a battery-cage confinement system is managed, all caged hens are permanently denied the opportunity to express most of their basic behavior within their natural repertoire. The science is clear that this deprivation represents a serious inherent welfare disadvantage compared to any cage-free production system. Cages and Alternative Systems Three basic housing systems are used in commercial egg production in the United States: battery cages, barns, and free-range. An estimated 95% 1 of the 280 million hens in the U.S. egg-laying flock 2 are confined in battery cages. 3 Egg industry guidelines recommend 432.3 cm 2 (67 in 2 ) of floor space per typical egg-laying hen, 4 and the most commonly used cages hold 5-10 birds per cage. 5 Cages are placed side by side, lined in rows, and stacked in tiers up to five levels high; tens of thousands of hens can be caged in a single building. Conventional battery cages provide a feed trough and water lines, but are otherwise barren environments. Scientists using preference testing techniques have demonstrated that hens generally prefer more space than is provided to them in a conventional battery cage. 6,7,8,9,10 Alternative laying hen housing systems, barns and free-range, vary widely both in design and management practices and requirements but, in contrast to battery cages, allow birds to move about freely. In barn systems, hens do not have outdoor access but are provided with nest boxes and often perches and loose substrate (litter or sand) for dustbathing, scratching, and foraging. Barns may be singleor multi-level structures. Single-level barns may be “deep-litter” systems, similar to the conditions in which broiler (meat-type) chickens are raised, or designed with perforated flooring, which allows manure to drop into a pit below. Multi-level barns (aviaries or * Dr. Shields received her Ph.D. in Animal Behavior from the University of California at Davis and serves as a consulting farm animal welfare scientist for the Humane Society of the United States. † Dr. Duncan is the Emeritus Chair in Animal Welfare at the University of Guelph, Ontario, and an internationally renowned expert on farm animal welfare science.