The Welfare of Hens in Battery Cages:
A Summary of the Scientific Evidence
A Farm Sanctuary Report

Introduction

Of all farm species, hens used for egg production are housed at the highest stocking densities (Keeling, 1995). In the U.S., hens are typically raised via the "battery system," in small groups in cages that are stacked in tiers and lined up in rows. The cage is typically a small enclosure with a sloping floor and equipment for feeding, drinking, and egg collection mounted on the front (European Commission, 1996, p.15). While the cage system is desired by producers for its efficiency in terms of labor (European Commission, 1996, p.73), it is widely acknowledged that there are significant welfare problems for laying hens in traditional cages (Appleby & Hughes, 1995). In several European countries, there has been pressure to ban the battery cage, which is thought of by much of the animal protection community as the most cruel of all production systems. Legislation was enacted in the Netherlands to ban battery cages (Preece & Chamberlain, 1993, p.216), and Sweden's Animal Protection Act of 1988 called for a phase-out of the battery cage (Keeling & Svedberg, 1999). In the U.S., less than 48 square inches of space may be provided per bird (Smith, 2000) as compared to 177-197 squared inches (450-500 squared centimeters) in the European Union (European Commission, 1996, p.15). Caged hens are strongly affected by the artificial design of the their environment and have less control over its effects than in any other system (Appleby et al., 1993). Battery cage systems fail to provide for the welfare needs of hens (Baxter, 1994).

After reviewing the scientific evidence relating to the welfare of hens in battery cages, Baxter (1994) concluded that hens housed in this way experience both chronic and acute suffering, as well as other threats to their welfare. The cage inhibits the performance of virtually all aspects of hen behavior (Rollin, 1995, p.120) due to the severe confinement and barrenness of the environment. Further, hens housed in the battery system cannot establish normal social relationships and cannot escape from aggressive cagemates (Rollin, 1995, p.119). Studies show that environments enriched with nest boxes, dust baths, and perches offer considerable benefits for welfare, allowing hens to take part in a wide variety of behavior patterns (Appleby & Hughes, 1991). Appleby and Hughes (1991) feel that the ideal system for laying hens should provide small group sizes with the freedom of movement and a complex environment. The cage system fails to do this.

The Hen's Natural Behavior

Dawkins has suggested that comparing farm animals' behavior with that of the species in the wild can be a starting point in the assessment of their welfare (Sherwin & Nicol, 1993). Dawkins' observations of Red Jungle Fowl (the ancestor of the domestic fowl) in semi-natural conditions have shown that even with food available at all times, birds spent most of the day foraging (Appleby & Hughes, 1991). When observed in a natural or semi-natural environment, both jungle fowl hens and domestic hens spend a large part of their active day time pecking and scratching at the ground (European Commission, 1996, p.35). Savory et al. observed that bantam hens foraging under natural conditions directed more than 14,000 pecks over a 10-hour daytime period (Hughes & Channing, 1998). Hens walk a lot when kept on free range (Rollin, 1995, p.120). Vestergaard's 1982 observational study of red junglefowl found that dustbathing, a sequence of coordinated movements that spread dust through the feathers, occurs on a regular basis and "takes up substantial time and energy of the birds" (Vestergaard et al., 1990). Vestergaard et al. (1992) found that feedback from dust may satisfy the bird's motivation to perform this behavior, and plays a role in ending a dustbathing bout.

The hen's motivation to nest is strong. Nesting is triggered by ovulation followed by the release of hormones from the egg follicle. In a natural environment, hens leave the social group and home range to select a nest site before egg laying (Baxter, 1994). Nest sites are typically secluded, enclosed by vegetation or contours in the ground. According to Appleby et al; and Wood-Gush, nesting behavior includes scratching, raking and gathering behaviors, and turning repeatedly in the nest. Duncan et al. observed that hens usually form a hollow "nest bowl" with loose material (e.g. dry grass or moss) (Baxter, 1994).

McBride et al.; Duncan et al., and Wood-Gush et al. have found that at night, hens will roost on the branches of bushes or trees (Baxter, 1994). Blockhuis suggested that hens' feet are adapted to close around a perch when sitting. It has been shown that hens are highly motivated to perch; Appleby et al. found that when perch space is limited, hens struggle "vigorously" to secure a perching position for the night (Baxter, 1994).

Hens have a carefully regulated social life and cohesive social group structure (Baxter, 1994). According to Appleby et al., spacing between the hens varies according to their activity-- hens will remain close together while roosting and preening, and will spread out while foraging (Baxter, 1994).

Scientific evidence suggests that the intensive confinement and barren environment of the battery cage fail to meet the hens' basic needs, causing physical and psychological suffering. Life in a Battery Cage

Lack of Space

One of the major issues giving rise to public concern over hen welfare is the degree of confinement in the battery cage (European Commission, 1996, p.15). Most Americans (86%) feel that the crowding of hens in commercial egg production is unacceptable (Zogby, 2000). According to Bogner et al., Freeman, and Dawkins & Hardie, the average hen occupies about 236 squared inches (600 squared centimeters) when at rest (Appleby & Hughes, 1991). This compares to a middle range of 48 to 54 squared inches of space given to caged hens in the U.S. (Smith, 2000). Dawkins & Hardie found that to carry out wing flapping, the hen requires nearly 787 squared inches (2000 squared centimeters) of space (Baxter, 1994). At the once 177 squared inches (450 squared centimeters) European space allowance, hens were forced to "frequently overlap or have their feathers compressed" (Appleby & Hughes, 1991). Even at a space allowance of 236 squared inches (600 sq. centimeters) per hen, there exists no free space. Thus, in theory, at this space allowance, hens must change places with each other in order to move around (Appleby & Hughes, 1991).

Of all the systems for raising laying hens, battery cage systems offer the least freedom of movement to the birds (Appleby & Hughes, 1991). In McLean et al.'s study comparing the perchery and cage system, hens in the perchery system moved an average of seven times the distance caged birds moved (Appleby & Hughes, 1991). Keeling (1994) found that as pen size decreased, walking and ground pecking decreased significantly and the frequency of standing (a "time-filler" behavior) increased. Bubier & Bradshaw, 1995 found that drinking took five times longer and was more frequent among caged birds than those on free range, and may have occurred in excess to fill available time, a possible indication of frustration.

General freedom of movement is generally associated with the freedom to perform specific behavior patterns (e.g., pre-laying behavior, comfort behavior, dust-bathing, pecking, and scratching), "the prevention of which might cause frustration" (Appleby & Hughes, 1991). Confinement in a battery cage "severely restricts hens' freedom to perform their full range of normal behaviours" (Baxter, 1994). Nicol found that comfort behavior (e.g. wing flapping, body shaking and stretching) is less frequent in battery cages than in systems offering hens more space, and the behavior of hens moved out of small cages suggests that constraints on comfort behavior cause frustration (Appleby & Hughes, 1991). Nicol observed the "rebound effect," that is, hens released from confinement will perform thwarted behaviors more frequently when released than do hens kept in spacious environments (Baxter, 1994). Bubier & Bradshaw, 1995 found that more wing-flapping occurred in hens on free range than in caged hens.

One behavioral theory states that hens frustrated by the inability to perform a particular behavior while confined will perform this behavior more frequently when released from confinement (Baxter, 1994). Testing this "behavioral rebound effect," Nicol found that hens kept in small cages (allowing 344 squared inches or 875 sq. centimeters for a single bird) for one and two months performed more tail wagging and wing flapping after release than hens kept in large cages offering 909 squared inches or 2310 sq. cm for the same periods of time. Leg stretching, wing stretching, and feather raising behaviors were also performed more frequently among the hens released from small cages than in birds kept in large cages (Baxter, 1994).

In choice tests for space, Hughes and Dawkins have shown that hens prefer a large cage over a small one (Faure, 1994). In a study in which hens could enlarge their cage by key pecking, Faure (1991) showed that hens are capable of learning an operant task to obtain space. According to Dawkins, hens prefer more vertical space than allowed in conventional European battery cages and make many head movements above 15.7 inches (40 cm) when unconstrained (Appleby & Hughes, 1991).

Crowding

Space is also used by animals in a social context-- to position themselves appropriately in relation to each other (Keeling, 1994). Being positioned at the appropriate distance from other birds, or inter-bird distance, for a particular activity "is an important aspect of the performance of that activity." Even if there is physical space to perform a particular activity, there may not be enough social space. As pen size decreases, behavior patterns which hens perform at the largest inter-bird distances (i.e. walking and ground pecking) decrease in frequency. The distance between birds when they are walking or ground-pecking is so important that when available space decreases, hens perform these activities less often rather than performing them at inappropriate inter-bird distances (Keeling, 1994).

Bubier & Bradshaw, 1995 found that pushing among birds occurred more frequently in the battery system than in birds on free range. Al-Rawi & Craig found that when space per hen was reduced from 1181 inches (3000 sq. cm) to 315 inches (800 sq. cm), aggression progressively increased (Baxter, 1994). Hens housed in battery cages usually attempt to feed at the same time, but cannot do so because the feeding trough is too narrow for them to stand side by side (Appleby & Hughes, 1991). There is increasing evidence that for small groups, even 4 inches or 10 cm (the EU minimum) of feeding space is inadequate (Appleby & Hughes, 1991).

The crowding of caged birds has resulted in significant welfare issues (Rollin, 1995, p.119). Hens have a carefully regulated social life and a cohesive social group structure (Baxter, 1994). When crowded, their social system breaks down "and the hens appear to be in a chronic state of social stress, perpetually trying to get away from their cagemates." The space allocation of 554 square inches (1408 sq. cm) per hen in Keeling & Duncan's 1989 study of spacing behavior in hens was insufficient for the hens' maintenance of natural social spacing. Further, social stress must result from the hens' continual adjustment of their social spacing in an attempt to keep themselves dispersed (Baxter, 1994).

Perching

Hens are adapted to perching, both physically and behaviorally (Baxter, 1994). Hens use perches extensively, both during the day and for roosting at night (Appleby & Hughes, 1991). They prefer to perch at night, and seem to be strongly motivated to do so (Baxter, 1994). In a barren environment with only a perch, hens will spend about half of the daytime perching (Baxter, 1994). In trials of a novel cage design that included a perch, Appleby & Hughes (1995) found that hens spent 32-37% of the day time on the perch, and at night, 92-98% of the birds roosted on the perch (Appleby & Hughes, 1995).

Use of a perch has been found to improve foot condition, may reduce foot and claw damage (Appleby & Hughes, 1991), and stimulates bone mass and strength (Baxter, 1994). A perch can also provide refuge for subordinate hens and allow them to avoid aggressive cage or penmates (Baxter, 1994). Webster and Hurnik; and Duncan et al. found that adding a perch to battery cages results in reduced feather wear (Baxter, 1994). McLean et al. found that hens housed in the perchery system were less aggressive than caged hens (Baxter, 1994). In their study of the effects of perch height on feather pecking, Wechsler & Huber-Eicher (1998) found that hens on the floor received more feather pecks than expected, while hens on perches were pecked less often than expected. Wechsler & Huber-Eicher (1998) conclude that hens should be provided with high perches during the laying period to reduce feather pecking and feather damage. Gentle & Hunter suggested that providing hens with high perches may reduce welfare problems tied to feather damage including pain caused by feather removal (Wechsler & Huber-Eicher, 1998). Without perches, there are potential welfare problems due to increased aggression, reduced bone strength, impaired foot condition, and higher feather loss (Baxter, 1994).

Nesting

There is much evidence that providing access to nests meets an important need of laying hens (Appleby & Hughes, 1991). A nest is "very attractive" to hens ready to lay (European Commission, 1996, p.34), and hens will work to gain access to nest sites during this time (Sherwin & Nicol, 1993). Sherwin & Nicol (1993) found that hens in modified cages with nests expressed a full repertoire of pre-laying activities. Sleeping, sitting on the nest, nest-building behaviors and crouching were all more similar to hens in extensive systems than to those observed in traditional cages. Indicators of frustration such as pacing were less frequent in the modified cages than in conventional ones (Sherwin & Nicol, 1993).

In a trial of a new cage design that included a nest, Appleby & Hughes (1995) showed that hens spend 5-6% of the day time in the nest, and they found that 91% to 96% of eggs were laid in the nest box (Appleby & Hughes, 1995). In a study comparing the behavior of hens housed in cages of various design, about 95% of eggs were laid in nest boxes in cages that had them (Smith et al., 1993). Of hens housed in all cage designs, pre-laying behavior was least disturbed in nest boxes, intermediate in dust baths, and most disturbed on the cage floor (Smith et al., 1993).

Birds may exhibit "very disturbed" behavior if a nest is not present (European Commission, 1996, p.34). When nesting is thwarted, hens may show a high degree of restlessness; others may sit and perform vacuum nesting behavior (Baxter, 1994). Such behaviors are widely accepted as indicating frustration. Baxter (1994) concluded that due to the intensity of nesting behavior and the degree of motivation to nest, "the frustration of nesting motivation is likely to cause significant suffering to the hen during the pre-laying period every day," and therefore causes acute suffering. The UK's Farm Animal Welfare Council (FAWC) has concluded that the inability to perform normal pre-laying behavior is one of the most important problems for the welfare of caged hens (Appleby & Hughes, 1991).

Flooring

There are two fundamental types of flooring used in commercial egg production: particles (wood shavings, straw, and sand) or mesh (wood, plastic, or metal) (European Commission, 1996, p.35). Battery cages generally have wire flooring that almost always consists of a lightweight rectangular mesh (Appleby & Hughes, 1991). Particle or litter floors allow for the normal performance of a wider range of behaviors, including scratching, dustbathing, and nesting; and are strongly preferred to floors without litter (European Commission, 1996, p.35). Hughes & Channing (1998) found that hens with access to litter spend about 18% of their time engaged in litter-related activities. Even when presented with a mild obstacle to the litter tray, hens continued to express the key behaviors of feeding and litter-related activities in the tray at the same rate as when no obstacle was present (Hughes & Channing, 1998). The wire floors of cages are very different from the substrates used for behavior patterns like nesting and dustbathing under natural conditions (Smith et al., 1993). Dawkins and Lagadic have shown that hens prefer litter to wire mesh when they have a choice (Faure, 1994).

Dustbathing

Domestic hens bathe only in dust (from sand, woodshavings, or similar loose, particulate matter) (Baxter, 1994). Dustbathing in poultry is a "highly motivated" behavior (Lindberg & Nicol, 1997) that has physical and behavioral effects (Appleby & Hughes, 1991). Vestergaard et al. and Liere describe dustbathing as having three stages: tossing, rubbing, and shaking; all in an attempt to regulate feather condition by removing excess oils (Baxter, 1994).

When comparing hens in battery cages to those on free range, dustbathing was "virtually nonexistent" in the hens in the battery system, and significantly greater in the free-range hens (Bubier & Bradshaw, 1995). When testing a new cage design that included a separate dust bath, Appleby & Hughes (1995) found that hens spent 5-7% of the day time in the bath. During a three hour afternoon observation period, an average of 61% of hens dustbathed (Appleby & Hughes, 1995).

Van Liere & Wiepkema (1992) found that when given a sand box, all hens performed dustbathing. In a behavioral study of hens housed in cages with a dust bath containing sand and those housed with access to a dust bath containing wood shavings, fully developed dustbathing occurred in both baths in bouts lasting 5-10 minutes (Smith et al., 1993). Appleby et al. (1993) also found that hens in enriched cages with dust baths typically performed dustbathing in the afternoon in a single bout lasting about 5 minutes. According to Gibson et al.; Appleby et al.; and Liere, hens with access to litter will dustbathe for about 10 minutes each day (Baxter, 1994). Vestergaard et al. (1992) found that feedback from dust may play a role in ending a dustbathing bout. Thus, dust may satisfy the birds' motivation to dust bathe.

Hens deprived of litter progressively increase their motivation to dustbathe, and will eventually develop sham or vacuum dustbathing behavior in which the hen "goes through the motions" of dustbathing on a bare floor (Baxter, 1994). Vestergaard et al. (1990) found that hens raised in a "poor" environment," that is, cages and pens with floors covered with wire mesh and no sand or grass still performed dustbathing (Vestergaard et al., 1990). Smith et al. (1993) found this in hens housed without a dust bath -- dustbathing behavior was performed on the bare floor in truncated form, as successive bouts each lasting about 10 seconds. Similarly, Appleby et al. (1993) found that hens in conventional cages performed brief and fragmented dustbathing behavior consisting of 3 bouts of 10 seconds each. During 21 weeks of sand deprivation, hens were observed dustbathing on a barren floor; some of these "sham dust baths" were abnormal, consisting of rubbing behavior only (van Liere & Wiepkema, 1992).

The inhibition of dustbathing causes frustration and chronic suffering (Baxter, 1994), and the motivation to perform this behavior increases during deprivation of dust (van Liere & Wiepkema, 1992). Norgaard-Nielsen (1997) observed a "rebound effect" on the intensity of dustbathing in hens from conventional cages given access to sand, "suggesting that a build-up of dustbathing motivation had taken place during rearing without sand." The physical and behavioral effects of dust baths suggests that the provision of dust baths makes a "significant contribution to the welfare of laying hens" (Appleby et al., 1993).

Foraging

When litter is available, hens use it intensively for scratching and pecking (European Commission, 1996, p.35). Keer-Keer et al., Petherick & Duncan, Savory et al., and Dawkins have shown that foraging is an important behavior for fowl -- that they are choosy about materials and spend significant amounts of time interacting with it (Hughes & Channing, 1998). Vestergaard et al. (1990) found that hens raised in cages with floors covered in white silica sand and grass sod "invariably directed their bill raking and scratching toward the sand or toward the earth provided." Bubier & Bradshaw, 1995 found that time spent pecking on the ground or cage floor was greater among birds on free range than in caged birds. In one study of hens raised in a strawyard, 47% of the birds' time was spent feeding and foraging (Appleby & Hughes, 1991). In Appleby et al.'s (1993) study of nesting, dustbathing, and perching by laying hens, hens used the dust bath for foraging (pecking and scratching) in addition to dustbathing. In hens housed with a perch and litter, Appleby & Hughes (1995) observed birds pecking at the sand while standing on the perch (Appleby & Hughes, 1995).

Feather pecking

Blockhuis has concluded that feather pecking is worse in barren conditions, probably due to the lack of varied stimuli for pecking (Appleby & Hughes, 1991). Thus, feather pecking is worse in battery cages than in other systems. Hens' ability to peck and scratch at "varied or manipulable" materials is thwarted in cages. According to Hughes and Duncan, this contributes to the occurrence of feather pecking and cannibalism in caged hens (Appleby & Hughes, 1991). The prevention of foraging causes hens to redirect ground pecking behavior into feather pecking aimed at their cagemates, causing pain, reduced feather cover, and heat loss (Baxter, 1994). Vestergaard et al. (1990) observed that birds raised on floors covered with wire mesh and no sand or grass directed bill raking and scratching toward cage/penmates. Norgaard-Nielsen (1997) also found that birds without sand tend to direct more feather pecks at the feathers of cage mates than do birds with access to sand. Hens kept in one battery cage system, which consists of slatted or wire flooring, "frequently show severe behavioral problems such as feather pecking and hysteria" (Appleby & Hughes, 1991). Feather pecking may lead to cannabilism (European Commission, 1996).

Ground pecking or foraging behavior when litter is provided reduces feather pecking (Baxter, 1994). Wechsler & Huber-Eicher (1998) found that the provision of foraging material had significant effects on the incidence of feather-pecking interactions among hens. Feather pecking occurred less in pens with polystyrene blocks for pecking than in pens without them. "Pulling" and "plucking" feather pecking interactions were significantly higher in pens without foraging material than they were in pens with foraging material (Wechsler & Huber-Eicher, 1998). Blockhuis and van der Haar have suggested that dust baths also provide hens with loose material for pecking, which may have some effect in reducing feather pecking (Appleby et al., 1993).

Physical Disorders

Plumage, Foot, & Claw Damage

Foot damage is common in laying hens kept in battery cages (European Commission, 1996, p.46). Disorders include lesions, fissures and hyperkeratosis on the feet and twisted, broken, or overgrown claws (Appleby & Hughes, 1991). It is thought that caged hens may have uncontrolled and excessive growth of the claws, which often leads to breakage of the claw that may inflict damage to the underlying tissues (European Commission, 1996, p.47). The thickness of the floor wire affects foot and claw damage (Appleby & Hughes, 1991). Steep flooring cages (which allow eggs to roll into collection trays) can also cause foot deformities (Rollin, 1995, p.126).

According to Fickenwirth et al., provision of sand may result in shorter claws and beaks, and prevent claw damage (Appleby & Hughes, 1991). In Smith et al.'s (1993) study of hens housed in conventional cages or with modified cages containing a dust bath of wood shavings or sand, hens in the modified cages had significantly less plumage, foot, and claw damage than hens without access to a dust bath. The majority of the damage was to the plumage of the neck, breast, tail and vent areas (Smith et al., 1993). Similarly, Appleby et al. (1993) found that feather, foot, and claw damage all tended to be less in enriched cages with perches, dust baths, and nest boxes than in conventional cages. It was concluded that claw and foot damage were likely reduced by dustbathing, scratching in the sand, and by the use of the nest boxes and perches (Appleby et al., 1993).

According to Appleby et al. and McLean et al., feather loss is generally worse in cages than in other systems (Appleby & Hughes, 1991). In McLean et al.'s study, feather loss in a perchery system was 2.67 compared to 4.35 in cages on a scale of 0 to 20. Norgaard-Nielsen found that birds without access to sand had a "significantly more deteriorated plumage" than birds in cages with a dust bath of sand. According to Hughes, feather loss from abrasion is typically worse in cages, and this is compounded by feather pecking (Appleby & Hughes, 1991). The wire mesh of the cage can lead to feather wear (Rollin, 1995, p.126).

Bone Weakness

Hens with high egg production tend to develop osteoporosis, or thinning of the bones due to the large demand for calcium in egg formation (Newberry et al., 1999). After laying eggs for a year, the hen's skeleton is fragile, depleted of calcium due to the production of many egg shells (Duncan, 2000). The disease is particularly serious in caged hens (Newberry et al., 1999). General freedom of movement is important for the hen's bone strength (Appleby & Hughes, 1991), and restriction of locomotion has physical effects (Appleby et al., 1993). The maintenance of bone strength depends upon the hen's ability to move normally (Baxter, 1994). Knowles & Broom found that the space provided in a battery cage does not allow the hens sufficient freedom of movement for adequate bone loading for the development of normal bone strength. Restricted movement prevents normal bone maintenance, particularly in the legs and wings (Baxter, 1994). Bone fragility in hens is a well-known condition that is related to the birds' ability to move and therefore keep bones and muscles healthy (European Commission, 1996, p.44). Since bone fragility may lead to bone fractures which are likely to cause pain (Newberry et al., 1999), the condition is key to hen welfare (European Commission, 1996, p.44).

McLean et al., Knowles & Broom, and Norgaard-Nielsen have shown that confinement in a battery cage reduces bone strength significantly (Baxter, 1994). Simonsen; Gregory and Wilkins found that 30 - 50% of caged birds suffer broken bones during catching, handling, and transportation (Appleby & Hughes, 1991). In comparison, hens raised on floors are able to exercise more. Rowland et al.; Meyer and Sunde found that floor-housed hens had as much as 41% more tibia strength than those raised in cages (Appleby & Hughes, 1991). Hughes & Appleby found that the availability of a perch significantly enhances bone strength (Baxter, 1994). McLean et al. found that hens raised in a perchery had tibias 40% stronger than cage-housed birds (Appleby & Hughes, 1991). Further, birds housed in cages have a greater incidence of lameness, bone brittleness, osteoporosis, and muscle weakness than hens kept in non-cage systems (Rollin, 1995, p.120).

Fatty Liver Hemorrhagic Syndrone (FLHS)

Fatty Liver Hemorrhagic Syndrome (FLHS), a condition characterized by a decreased laying rate and possible sudden death from rupture of the liver, is another disease mainly encountered in caged hens (European Commission, 1996, p.45). Squires and Leeson found that factors responsible for FLHS are stress and lack of exercise due to confinement and crowding (European Commission, 1996, p.46).

Injuries from Equipment

The cage structures and failing of equipment involved in egg production can cause the hens to suffer. The breakdown of automatic feeders and drinkers can lead to severe welfare problems, and limited access to feed can lead to aggression and cannibalism (Appleby & Hughes, 1991). Trapping body parts in the cage is another welfare problem associated with the battery system. Most commonly, it is the head or neck that is trapped, which can lead to severe trauma or death (Appleby & Hughes, 1991). An investigator from Compassionate Action for Animals documented an equipment-related incident at a battery cage egg facility: "The hens can not stand up without hitting their heads on the "roof" of the cage, which is actually a conveyor belt used to collect and remove droppings from the tier of cages directly above them. We found a hen who apparently stood up while the conveyor belt was running, causing her head to be pulled over the cage divider into the next cage. When we found her, her head was still trapped and she was dead - possibly from trauma, suffocation, or dehydration" (Compassionate Action for Animals, personal communication, December 2000).

Beak Trimming (also known as debeaking)

The partial amputation of the beak, also known as beak trimming or debeaking, is performed by removing one-third to one-half of the upper mandible and often the same part of the lower one with a heated blade, which cuts and cauterized (European Commission, 1996, p.49). Its purpose is to prevent or reduce cannabalism and feather pecking (Gentle et al., 1990). According to Rollin (1995), beak trimming "causes behavioral and neurophysiological changes betokening both acute and chronic pain" and "represents a major welfare issue."

The avian beak is a complex sensory organ which serves to grasp food particles, manipulate nesting materials, for nesting exploration, drinking, preening, and for defense (Gentle et al., 1990). According to Gentle, to enable a bird to perform all of this, the chicken beak has "an extensive nerve supply." According to Gentle, beak trimming results in the formation of large neuromas, or bundles of nerve tissue, in the healed stump of the beak. Thus, beak trimming is "likely to be a painful procedure" characterized by tissue damage, pain, and anxiety. Further, Fraser & Quine suggested that the behavioral changes associated with beak trimming "point to the possibility of depression" (Gentle et al., 1990).

Gentle et al.'s study of the behavior of hens after the beak trimming procedure found that beak trimming caused several significant behavior changes in the birds. Post surgery, the bird may experience increased sleep, inactivity, and disturbances of eating, grooming, and social behavior (Gentle et al., 1990). Following beak trimming, the hens pecked at the environment less than they did before the surgery. The control group of birds without beak damage wiped their beaks more after contact with water, but the beak-trimmed birds did not. There was a consistent reduction in beak wiping during the 6-week period following surgery, whereas this activity was unchanged in the control group of hens. Post surgery, hens also showed reductions in head-shaking behavior, which is associated with feeding and drinking, and functions to remove food and other particles from the mouth or surface of the beak. These changes in environmental pecking, wiping, and head shaking were interpreted as guarding behavior of the painful area. The debeaked hens drank less post-operatively, and pecked less than they did before surgery. Duncan et al. found a significant reduction of the use of the beak for activities like preening and exploratory pecking for at least five weeks after the procedure (Gentle et al., 1990).

According to the European Commission (1996, p.54), debeaking may cause birds acute and chronic pain, sensory deprivation, reduction in feeding, and suppression in growth. Further, it has had "varying success in controlling feather pecking and cannibalism" (European Commission, 1996, p.54). In 1987, the UK's Ministry of Agriculture, Food, and Fisheries (MAFF) recommended that beak trimming be carried out only as a last resort (Appleby & Hughes, 1991).

Forced Molting

Under natural conditions, hens are stimulated to lay eggs by increasing daylight (Duncan, 2000). When enough fertile eggs accumulate in the nest, the hen incubates the eggs for 21 days, during which time food intake drops significantly due to a change in hormone level. After hatching, the hen looks after a family of chicks for a number of weeks. Before the summer is out, there may be time for the hen to lay a second clutch of eggs and raise another group of chicks. When daylight decreases in the fall, the hen will stop laying and begin molting, or shedding feathers, which are gradually replaced after molting (Duncan, 2000).

Commercial egg producers employ "forced molting" as a means of expediting the natural egg-laying cycle (Rollin, 1995, p.125). In forced molting, birds are deprived of food for up to 12 days and water for up to 3 days, and daylight is withdrawn (Rollin, 1995). This brings about a change in hormone levels and forces hens out of reproductive condition (Duncan, 2000). Old feathers are forced out and the laying cycle is resumed (Rollin, 1995). Overall, forced molting shortens the molting process from 16 weeks in natural conditions to 8 weeks (Millman, 2000).

Forced molting is a traumatic procedure for hens (Rollin, 1995) that results in "tremendous stress and suffering" (Millman, 2000). Mortality increases dramatically during forced molting (Duncan, 2000); disease susceptibility is also heightened (Millman, 2000). Forced molting has been banned in most European countries due to the cruelty involved (Duncan, 2000).

Conclusion

The welfare of hens in battery cages is severely impaired. In a natural environment, hens walk, forage, peck and scratch at the ground, dustbathe, nest in secluded areas with grasses and other loose material, and perch on branches. It has been found that hens are strongly motivated to perform these behaviors and require adequate space and environmental conditions to do so. Chickens also develop a complex social system which depends on inter-animal spacing. The battery system crowds and confines hens tightly in a barren environment, such that the birds cannot move freely or perform normal behaviors. These conditions cause the birds to experience frustration and social stress which can lead to feather pecking among other problems. Physical injuries common in the cage system include: plumage, foot and claw damage, bone weakness, and liver disease. Further, the practices of beak trimming and forced molting cause pain and trauma. Thus, the battery cage system puts hens in a perpetual state of physical and psychological suffering.

References

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