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Chickens in Battery Cages.
In poultry farming, battery cages (often called laying cages in the United States or battery farming in the United Kingdom) are an industrial agricultural confinement system used primarily for egg-laying chickens. The battery cage has generated controversy among advocates for animal welfare and animal rights and industrial egg producers.

It is estimated that over 60% of the world’s eggs are produced in industrial systems, mostly using battery cages, including over three quarters in the EU.


A chicken coop from the 1950s
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 early date, battery cages already had the sloped floor that allowed eggs to roll 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 manure, which provides better air control quality and eliminates fly breeding.

Original 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 from Arndt about battery cages were enthusiastic. Arndt 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 1960s. The practice of battery cages was criticized in the book Animal Machines, published in the 1960s.

In 1990, North and Bell reported that 75% of all commercial layers in the world and 95% in the United States 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.

Disadvantages 1 and 2 can be eliminated by manure conveyors as pioneered by Arndt, but some industrial systems do not feature manure conveyors.

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.


European Union

Battery cages are due to be banned in the European Union from 2012 after a 10-year phaseout, to be replaced by 'enriched' cages. The 1999 EU Hens Directive bans the conventional battery cage from 2012. In their 1996 report, the European Commission’s Scientific Veterinary Committee (SVC) condemned the battery cage, concluding:
“It is clear that because of its small size and its barrenness, the battery cage as used at present has inherent severe disadvantages for the welfare of hens”.

The EU Hens Directive allows ‘enriched’ cages to be used. Under the directive, ‘enriched’ cages must be at least 45 cm. high and must provide each hen with at least 750 cm² of space; 600 cm² of this must be “usable area” – the other 150 cm² is for a nest-box. The cage must also contain litter, perches and “claw-shortening devices”. Some animal welfare organisations such as Compassion in World Farming have criticised this move, calling for ‘enriched’ cages to be prohibited as they believe they provide no significant or worthwhile welfare benefits as compared with conventional battery cages.

Germany has prohibited ‘enriched’ cages from 2012. Germany has also banned conventional cages from 2007, five years earlier than required by the EU Directive. The use of Battery Cages is banned also in Switzerlandmarker, Belgiummarker, Austriamarker, Swedenmarker and the Netherlandsmarker.


Battery Cages have been banned in Switzerland since 1.1.1992. It has been the first country to do so.

United States

The passage of California Proposition 2 aimed, in part, to reduce or eliminate the problems associated with battery cages, by setting the standard for space relative to free movement and wingspan, rather than cage size.

Cage size

Floor space for battery cages range from 300 cm² per bird and up. EU standards in 2003 called for at least 550 cm² per hen. In the US, the current recommendation by the United Egg Producers is 67 to 86 in² (430 to 560 cm²) per bird.

The space available to battery hens has often been described as less than the size of a piece of paper. A4 sized paper has an area of ≈ 97 in² (625 cm²), while letter sized paper has an area of ≈ 93.5 in² (603 cm²). A typical cage is about the size of a filing cabinet drawer and holds eight to 10 hens. Hens in battery cages do not have room to lie down or stretch their wings.

Animal welfare

Battery cage

The main contentious issue of battery cages relates to the welfare of the hens. Several studies have indicated 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 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". Hens in battery cages are said to experience elevated stress and aggression levels, but a 2008 study states that there is no detectable difference in stress levels based on housing.

Battery cages

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 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 environmental enrichment, feeding mash instead of pellets, keeping roosters in with the hens, and arranging nest boxes so hens are not exposed to each others' rears.

Human health

Research has shown that the risk of salmonella is likely to be higher in intensively produced eggs in comparison to free-range or organic produced eggs.

See also


  1. Compassion in World Farming - Welfare issues for egg laying hens
  2. Compassion in World Farming - 'Enriched' cages for laying hens]
  4. Chickens: Layer Housing, Michael C. Appleby, Encyclopedia of Animal Science. DOI: 10.1081/E-EAS-120019534
  5. Housing, space, feed and water United Egg Producers
  6. Ibid
  8. Compassion in World Farming - Human health - Factory Farming and Human Health

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