In poultry farming, battery cages (often called factory farming in the United States or battery farming in the United Kingdom) are an industrial agricultural confinement system used primarily for egg-laying hens. Although the term is usually applied to poultry, similar cage systems are used in fur farming for mink, chinchilla and foxes. 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.[1] In the UK, statistics from the Department for the Environment, Food and Rural Affairs (Defra) indicate that 50% of eggs produced in the UK throughout 2010 were from cages (45% from free-range, 5% from barns).[2]
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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.[3] 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.[3]
Original battery cage 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.[3]
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."[3]
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.[4]
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.[5]
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[5]
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.[5]
Disadvantages 1 and 2 can be eliminated by manure conveyors as pioneered by Arndt, but some industrial systems do not feature manure conveyors.[6]
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.
In 1999, the European Union Council Directive 1999/74/EC[7] banned the conventional battery cage in the EU from 2012, after a 10-year phase-out. 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 Directive allows enriched or "furnished" 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. The use of battery cages is banned in Belgium, Austria, Sweden and the Netherlands.
Germany has banned conventional battery cages from 2007, five years earlier than required by the EU Directive,[8] and has prohibited enriched cages from 2012. Mahi Klosterhalfen of the Albert Schweitzer Foundation has been instrumental in a strategic campaign against battery cages in Germany.[9]
Battery cages have been banned in Switzerland since January 1, 1992. It has been the first country to do so.[10]
The passage of California Proposition 2 (2008) 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.
The 2009 'Code of Practice' permits the use of battery cage. A written commitment by government to review the practice was scheduled in 2010. There was no further communication. A recent national survey showed that 86% of Australians believe that battery cages are cruel.[11]
In countries with relevant legislation, floor space for battery cages ranges upwards from 300 cm2 per bird. EU standards in 2003 called for at least 550 cm2 per hen.[12] In the US, the current recommendation by the United Egg Producers is 67 to 86 in2 (430 to 560cm2) per bird.[13] The space available to each hen in a battery cage has often been described as less than the size of a sheet of A4 paper.[14] Others have commented that a typical cage is about the size of a filing cabinet drawer and holds eight to 10 hens.[6][15]
Behavioural studies showed that when turning, hens used 540 to 1006 cm2, when stretching wings 653 to 1118 cm2, when wing flapping 860 to 1980 cm2, when feather ruffling 676 to 1604 cm2, when preening 814 to 1270 cm2 and when ground scratching 540 to 1005 cm2.[16] A space allowance of 550 cm2 would prevent hens in battery cages from performing these behaviours without touching another hen. Animal welfare scientists have been critical of battery cages because of these space restrictions[17] and it is widely considered that hens suffer boredom and frustration when unable to perform these behaviours.[18] Spatial restriction can lead to a wide range of abnormal behaviours, some of which are injurious to the hens or their cagemates.
Several studies have indicated that a combination of high calcium demand for egg production and a lack of exercise can lead to osteoporosis. This can occur in all housing systems for egg laying hens, but is particularly prevalent in battery cage systems where it has sometimes been called 'cage layer osteoporosis'.[19] Osteoporosis leads to the skeleton becoming fragile and an increased risk of bone breakage, particularly in the legs and keel bone. Fractures may occur whilst the hens are in the cage and these are usually discovered at depopulation as old, healed breaks, or they might be fresh breaks which occured during the process of depopulation. One study showed that 24.6% of hens from battery cages had recent keel fractures whereas hens in furnished cages, barn and free-range had 3.6%, 1.2% and 1.3% respectively. However, hens from battery cages experienced fewer old breaks (17.7%) compared to hens in barn (69.1%), free-range (59.8%) and furnished cages (31.7%).[20]
To reduce the harmful effects of feather pecking, cannibalism and vent-pecking, hens going into battery cages are beak-trimmed, a procedure considered to cause acute pain and distress with possible chronic pain. Beak-trimming occurs for hens in all types of housing systems, not only battery cages.
To reduce the harmful effects of feather pecking, cannibalism and vent-pecking, hens in battery cages (and other housing systems) are often kept at low light intensities (e.g. less than 10 lux). Low light intensites may be associated with welfare costs to the hens as they prefer to eat in brightly lit environments[21] and prefer brightly lit areas for active behaviour but dim (<10 lux) for inactive behaviour.[22] Dimming the lights can also cause problems when the intensity is then abruptly increased temporarily to inspect the hens; this has been associated as a risk factor of increased feather pecking[23] and the birds can become frightened resulting in panic-type ("hysteria") reactions which can increase the risk of injury.
Being indoors, hens in battery cages do not see sunlight. Whilst there is no scientific evidence for this being a welfare problem, some animal advocates indicate it is a concern.[24][25] Furnished cages and some other non-cage indoor systems would also prevent hens seeing natural light throughout their lives.
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".[19] Supporters of battery farming contend that alternative systems such as free range also have welfare problems, such as increases in cannibalism, feather pecking and vent pecking. A recent review of welfare in battery cages made the point that such welfare issues are problems of management, unlike the issues of behavioral deprivation, which are inherent in a system that keeps hens in such cramped and barren conditions.[26] Free range egg producers can limit or eliminate injurious pecking, particularly feather 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' vents;[26] similar strategies are more restricted or impossible in battery cages.