An HSUS Report: A Comparison of the Welfare of Hens in Battery Cages and Alternative Systems | Prepared by Drs. Shields and Duncan
An HSUS Report: A Comparison of the Welfare of Hens
in Battery Cages and Alternative Systems
Sara Shields, Ph.D.,
and Ian J.H. Duncan, Ph.D.
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
) 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, wing-
flapping, 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,
An estimated 95%
of the 280 million hens in the U.S. egg-laying flock
are confined in battery cages.
industry guidelines recommend 432.3 cm
) of floor space per typical egg-laying hen,
and the most
commonly used cages hold 5-10 birds per cage.
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.
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 single- or multi-level structures. Single-level
Dr. Shields received her Ph.D. in Animal Behavior from the University of California at Davis and serves as a consulting