The battery cage system for laying hens was introduced commercially on a wide scale in the 1950’s. Since that time, it has become the predominant method for maintaining hens. Cages provide the egg producer with an efficient and cost-effective means of collecting eggs, disposing of wastes, reducing feed wastage, maintaining an adequate environmental temperature, and inspecting the condition of individual birds.
Cages have come under increasing criticism, however, largely because of the behavioral restrictions that are imposed upon the birds. Cages do not provide an environment that allows the expression of behaviors like nesting, perching, and dustbathing. Space allowances for laying hens have also been criticized, although how space allowances should be determined is an extremely controversial topic (1). In their “Recommended Guidelines of Husbandry Practices for Laying Chickens,” the United Egg Producers suggest 48 square inches per bird as a minimum space requirement for caged hens; however, the European Community has mandated a minimum allowance of 75 square inches per bird.
(In many European countries, heavier bodied brown egg layers are preferred to the lighter bodied white egg layers used in the United States. Both the European and UEP guidelines can therefore be interpreted as providing a minimum space allowance of 12 square inches per pound of liveweight, although it is more common to express space allowances on a per-bird basis.) Some European countries have either increased this allowance or outlawed battery cages entirely. Several alternative production systems are being investigated in Europe. These vary from more intensive systems like the get-away cage or the Edinburgh cage (modified battery cages containing perches, dustbaths, and nestboxes) to more extensive systems like aviaries, straw yards, and free range (2,3,4).
It is still unclear whether the more extensive alternative systems will prove to be economically viable and also result in improvements in welfare. In general, both egg prices and mortality have been found to increase in these systems. In Britain, for example, free range eggs cost about 50 percent more to produce than cage eggs (5), largely due to increased labor costs. Mortality is approximately 4 percent in cages, 9 percent on litter, and 16 percent on range (6). Most mortality on litter is due to cannibalism, which represents an important welfare problem for the bird that must be carefully balanced against the importance of providing opportunities for the expression of behaviors. In general, cages still provide the best means for insuring bird health and egg quality and safety. The cage manufacturer’s recommendations for stocking density should be followed. Modified cages like the Edinburgh cage (4) are promising alternatives to conventional cages.