In industrial agriculture, battery cages (called laying cages in the United States) are a confinement system used primarily for egg-laying hens. The battery cage has generated controversy among advocates for animal welfare and animal rights.
An early reference to battery cages appears in Milton Arndt's 1931 book, Battery Brooding, where he reports that his cage flock was healthier and had higher egg production than his conventional flock. At this date battery cages already sported the sloped floor that allowed eggs to roll out to the front of the cage, where they were easily collected by the farmer and out of the hens' reach.
Arndt also mentions the use of conveyor belts under the cages to remove the manure, which gives a superior ability to control air quality and eliminate fly breeding than other methods.
Battery cages were an extension of the technology used in battery brooders, which were cages with a wire mesh floor and integral heating elements for brooding baby chicks. The wire floor allowed the manure to pass through, removing it from the chicks' environment and eliminating manure-borne diseases.
Early battery cages were often used for selecting hens based on performance, since it is easy to track how many eggs each hen is laying if only one hen is placed in a cage. Later, this was combined with artificial insemination, giving a technique where each egg's parentage is known. This method is still used today.
Early reports about battery cages were enthusiastic. Ardnt reported:
This form of battery is coming into widespread use throughout the country and apparently is solving a number of the troubles encountered with laying hens in the regular laying house on the floor.
In the first edition of this book I spoke of my experimental work with 220 pullets which were retained for one year in individual cages. At the end of this year it was found that the birds confined in the batteries outlaid considerably the same size flock in the regular houses. The birds consume less feed than those on the floor and this coupled with the increased production made them more profitable than the same number of pullets in the laying house.
A number of progressive poultrymen from all over the United States and some in foreign countries cooperated with me in carrying on experimental work with this type of battery and each and every one of them were very well satisfied with the results obtained. IN fact, a number of them have since placed their entire laying flocks in individual hen batteries.
The use of laying batteries increased gradually, becoming the dominant method somewhat before the integration of the egg industry in the Sixties. In 1990, North and Bell reported that 75% of all commercial layers in the world and 95% in the U.S. were kept in cages.
By all accounts a caged layer facility is more expensive to build than high-density floor confinement, but can be cheaper to operate if designed to minimize labor.
North and Bell report the following advantages to laying cages:
1. It is easier to care for the pullets; no birds are underfoot.
2. Floor eggs are eliminated.
3. Eggs are cleaner.
4. Culling is expedited.
5. In most instances, less feed is required to produce a dozen eggs.
6. Broodiness is eliminated.
7. More pullets may be housed in a given house floor space.
8. Internal parasites are eliminated.
9. Labor requirements are generally much reduced
They also cite disadvantages to cages:
1. The handling of manure may be a problem.
2. Generally, flies become a greater nuisance.
3. The investment per pullet may be higher than in the case of floor operations.
4. There is a slightly higher percentage of blood spots in the eggs.
5. The bones are more fragile and processors often discount the fowl price.
Note that disadvantages 1 and 2 can be eliminated by manure conveyors as pioneered by Arndt.
In general, farmers and poultry scientists who have used both floor confinement and cages do not seem to have felt that cages were either ineffective or inhumane, though there was considerable criticism of individual installations that were too expensive or were poorly designed to yield the all-important reduction in labor inputs.
The main disadvantages of battery cages relate to the welfare of the hens. Several studies have indicated for example that a combination of high calcium demand for egg production and a lack of exercise lead to a painful condition known as cage layer osteoporosis, which increases the chances that hens in battery cages will break their bones.
However, it is the behavioural effects of keeping hens in cramped and barren conditions that is the main concern of both animal welfare organisations and scientists studying animal welfare. The Scientific Veterinary Committee of the European Commission for example stated that "enriched cages and well designed non-cage systems have already been shown to have a number of welfare advantages over battery systems in their present form".
Animal Welfare scientists have been critical of battery cages because they do not provide hens with sufficient space to stand, walk, flap their wings, perch or make a nest, and it is widely considered that hens suffer through boredom and frustration through being unable to perform these behaviours
Supporters of battery farming contend that alternative systems such as free range also have welfare problems, such as increases in cannibalism and injurious pecking. A recent review of welfare in battery cages however made the point that such welfare issues are problems of management unlike the issues of behavioural deprivation, which are inherent in a system that keeps hens in such cramped and barren conditions. Free range egg producers can limit or eliminate injurious pecking through such strategies as providing environmenal enrichment, feeding mash instead of pellets, keeping roosters in with the hens, and arranging nest boxes so hens are not exposed to each others' backsides
Following advice from the European Scientific Veterinary Committee and lobbying from animal welfare groups the European Commission passed Council Directive 1999/74/EC phasing out battery cages by 2012.. Germany moved to include enriched cages in the phase out (Bill passed by Bundesrat on 19 October 2001). Battery cages have also been banned in Switzerland since 1992, in Sweden since 1999 and in Finland since 2005.
The New Zealand government was under a great deal of pressure to phase out battery cages after the Animal Welfare Act of 2000 stipulated that animals must be able to "display normal patterns of behaviour". However, in spite of the requirements of the Act, and extensive support from the public, the New Zealand government declined to phase out battery cages, and there is strong evidence that this was due to industry pressure on government .
California will have a ballot initiative, Proposition 2 (Prevention of Farm Animal Cruelty Act) on the November 2008 ballot which would ban severe confinement of egg-laying hens, as well as veal crates and sow gestation crates.