Feather pecking

Chickens in modern livestock farming often show abnormal behavior due to stress, which likely comes from growing up without a mother.

For example, "gentle feather pecking" is a natural social behavior in chickens. However, this gentle pecking can escalate to more aggressive pecking, which may damage and pull out feathers. This results in bald patches, and the pecking can extend to the chicken's skin (known as cannibalistic pecking), leading to wounds. The sight of blood triggers even more intense pecking and can eventually lead to cannibalism. This represents the final stage of feather pecking and often results in death. Feather pecking often also includes pecking at combs, wattles, legs, and the cloaca (the gut, urine, and egg duct). Incidentally, this intensive feather pecking has nothing to do with the "pecking order," as pecking specifically targets the head or neck and rarely leads to feather loss. ^[30] . This feather pecking does not occur in the wild, but wild chickens also show feather pecking when kept in captivity, indicating that the primary cause is stress.

Feather pecking is a tough and ongoing issue that leads to serious welfare concerns. This problem is especially challenging for farmers when chickens are free-range and their beaks are not trimmed. In free-range settings, farmers find it harder to keep an eye on feather pecking. Additionally, untrimmed beaks can inflict more damage than trimmed ones.

Feather pecking is influenced by several factors. The key factors include the mother's care of her chicks and the stress she experiences, the feeding and foraging behaviors of both young and adult animals, and the impact of stress and anxiety overall ^[31] . Genetic factors also contribute. Unfortunately, much of the research aimed at preventing feather pecking primarily addresses the economic losses it causes, often neglecting the welfare of the hens.

As we have observed, chicks develop without their mothers. They hatch in an incubator and then grow alongside other chicks. Although chickens become independent shortly after hatching, their mothers guide them on what to peck, when to rest, and how to act. The lack of a mother in contemporary laying hen farming likely has a significant and often overlooked impact on how chicks and hens interact with each other and their capacity to exhibit normal or natural behaviors. ^[32] .

Litter and other distractions can help reduce feather pecking, but they aren't enough on their own. For instance, chickens from organic farms that have litter and free-range access to the outdoors still show signs of feather pecking.

Chickens tend to peck more aggressively at unfamiliar chickens compared to familiar ones. However, in larger flocks, pecking often decreases. This likely happens because there are so many unfamiliar chickens that it's impossible to chase away all the "competitors."

Each year, around 54 million chickens have their beaks shortened (burned) to prevent injuries from pecking ^[33] . Since 2015, beak shortening has only been allowed using infrared radiation, which produces intense heat that causes beak tissue to die within a few weeks, resulting in the tip of the beak falling off. Starting in 2018, beak shortening will be banned by law. ^[34]

Research has been ongoing regarding selective breeding to reduce aggression and provide more spacious environments to prevent beak pecking, especially in light of the ban on beak trimming. ^[35] However, beak pecking continues to be the primary welfare issue for laying hens. A investigation conducted in 2006 across 29 different organic farms revealed that the situation was still concerning. ^[36] Research from 2017 indicates that there is still much to learn about feather pecking, particularly regarding effective prevention methods. ^[37] The question remains whether the ban on beak trimming is merely shifting one welfare issue while worsening another.

Failure and diseases

When farmers began raising laying hens on a large scale, the rate of premature deaths (failure) increased from 5-6% to as high as 20%. ^[38] This rise was primarily due to the spread of diseases caused by overcrowding. Only through various artificial interventions, such as vaccination, could the mortality rate be lowered. The use of battery cages was also a response to this issue; it significantly reduced contact between hens and kept them separated from their droppings. However, with the abolition of battery cages, some of these problems are resurfacing. Research has shown that in housing systems where laying hens are no longer confined to cages, there is a higher incidence of (old) diseases, likely because chickens have more contact with each other and their droppings, which harbor many pathogens. ^[39]

Generally, the mortality rate during the laying season shows a clear pattern. The initial period when a flock of laying hens is introduced to a barn is very stressful. For instance, chickens may crush one another, begin pecking at feathers, or suffer slow deaths due to an inability to find water and/or food in the new coop. Once the chickens adjust to their new environment, mortality between 30 to 50 weeks remains relatively stable and low (up to about 2%). However, after 50 weeks, the mortality rate rises again to around 8%, primarily because the hens are already "worn out," leading to decreased resistance. ^[21]

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A distinction can be made between "natural" death and death caused by disease. Natural death is often associated with egg laying. A recent American study found that 26.6% of laying hens that died "naturally" succumbed to Egg Yolk Peritonitis (EYP). ^[40] The oviduct is a funnel-shaped structure that collects the egg as it is released from the ovary. In laying hens, this process can frequently fail or even stop permanently, causing the egg to enter the abdominal cavity instead of the oviduct. Undeveloped eggs can accumulate there and become infected, ultimately leading to death.

Chickens can catch various diseases and parasites. This is partly because selective breeding for maximum egg production has weakened their immune systems, making them less resistant. ^[41] Additionally, the chickens often experience stress, which further decreases their resistance. ^[42] Furthermore, laying hen houses provide perfect conditions for disease spread due to the high density of birds, the consistently warm temperatures throughout the year, damp and dark areas, and contact with their own feces (manure).

Red mites or bird mites

The red mite has become well-known and infamous due to the fipronil scandal, which led to the culling of over 2.5 million healthy chickens. The term "red mite" is actually a misnomer; it refers to the poultry mite, which is a type of mite, not a louse. This is the most common parasite found in laying hens across Europe. In the Netherlands, 94% of poultry farms are infested with these mites, and a single chicken can harbor between 50,000 and 500,000 mites. The poultry mite is also capable of transmitting viruses and bacteria. The hens experience stress from the itching caused by the mites, leading them to peck at the mites and injure their own feathers. This itching and stress can also trigger increased aggressive behavior, which exacerbates feather pecking. Ultimately, the hens may die from blood loss and/or severe feather pecking. ^[43] As a result, fewer eggs are produced, and the quality of the eggs decreases.

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The poultry mite flourishes in the highly unnatural conditions that laying hens endure.

E. coli

An infection with the bacterium Escherichia coli (E. coli) is a leading cause of mortality. [source title="21"] This infection typically involves a specific type of E. coli known as APEC (Avian Pathogenic E. coli), and the disease it causes is called colibacillosis.

E. coli thrives at temperatures between 18-44°C, making the barn climate perfect for its growth, as it maintains a steady temperature of around 20°C.

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Bird flu

Avian influenza is likely the most recognized disease affecting chickens, mainly because it frequently makes headlines due to the numerous cullings. Bird influenza has two types: the mild variant, known as low pathogenic, and the dangerous variant, called highly pathogenic or avian flu. Animals infected with the mild variant usually show few symptoms. However, laying hens are still culled since this mild variant can evolve into the dangerous form. In rare instances, some types of bird influenza can also infect humans.

In 2003, avian influenza devastated the poultry industry, destroying one-third of all poultry farms. Thirty million birds were killed using electric shock or gassing. The H7N7 strain infected 89 people, and one of them did not survive.

In 2016, the industry culled over 1 million laying hens due to the H5N8 strain to stop its spread to other farms. That year also saw the longest indoor confinement of chickens in the Netherlands, lasting five months. Fortunately, this strain did not spread to humans.

In December 2017, avian influenza was detected on a meat farm, leading to the culling of 16,000 ducks. Since the virus was suspected to be a highly pathogenic H5 strain, authorities issued a nationwide order to confine birds indoors.

Free-range poultry are at a higher risk of contracting bird flu ^[49] . Wild (migratory) birds, like ducks and geese, are often blamed for spreading the disease to laying hens. However, research from 2014 indicates the opposite; migratory birds do not introduce the virus into the country, but instead contract it here ^[50] .

Vaccination against bird flu is feasible; however, it is not primarily pursued for economic reasons. The process is challenging and costly, and our key export partner, Germany, does not accept products from vaccinated animals. ^[52] .

This disease thrives in chickens due to the unnatural conditions they are kept in. Low resistance, high chicken densities, and a barn climate that is damp, dark, and warm create the perfect environment for the virus.

Sternum abnormalities

A 2015 Flemish study found that after 60 weeks, 60% of laying hens in aviary houses exhibited a breastbone abnormality ^[54] . Research conducted by the Institute for Agricultural and Fisheries Research (ILVO) in 47 Belgian aviary hen houses revealed that an alarming 82.5% of hens had experienced one or more fractures by the end of the production cycle. In comparison, this percentage was 58% for floor-fed hens and 62% for those in enriched cages. ^[55] . The ILVO study also indicated that 59.8% of the hens examined had a curvature (deviation) of the breastbone ^[56] . Deviations are primarily caused by the shape and material of perches; hard, inflexible materials lead to greater deformations of the sternum compared to softer, flexible materials ^[53] . When a hen perches, two-thirds of her weight is supported by her breastbone.

Fractures and their repairs greatly affect the well-being of hens. Research indicates that hens with repaired fractures experience chronic pain. ^[57] . Moreover, repaired fractures limit the hen's mobility and negatively influence egg production. ^[58] .

Osteoporosis

Bone loss, or osteoporosis, is a major cause of weak bones and fractures, often exacerbated by insufficient exercise. Laying a large number of eggs places significant demands on a hen's body. For instance, the calcium required for the eggs a hen lays during a laying period is 20-30 times more than what she can store. ^[59] . As calcium is drawn from the bones to form the eggshell, the bones become more fragile. This increases the likelihood of fractures, particularly towards the end of the laying cycle, which can be very painful. In cages, where laying hens experience greater bone decalcification due to restricted movement, it is estimated that 80 to 89% of them suffer from osteoporosis ^[60] . It has also been estimated that 13 to 35% of deaths in cages are attributed to osteoporosis. In free-range barns, although the overall mortality rate is higher, the proportion of deaths due to osteoporosis is lower. ^[35] .

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A recent American study revealed that among the laying hens that died 'naturally', up to 16.8% had succumbed to hypocalcemia ^[40] . Hypocalcemia is a condition characterized by insufficient calcium in the blood, as most of the calcium is redirected to egg production. This deficiency can lead to muscle cramps, and the chickens may die from suffocation.

Foot problems

Foot and sole problems are common in poultry, including hyperkeratosis, footpad dermatitis, and bumblefoot. Key factors contributing to these issues include the type of barn, wet litter, perch and flooring materials, perching behavior, and poor leg hygiene.

Hyperkeratosis is a severe thickening of the skin on the feet due to excessive keratin production. Footpad dermatitis is an inflammation beneath the skin of the foot's sole, which can result in dead tissue and ulcers. In severe cases, this condition may progress to spherical lesions and swelling, known as "bumblefoot," which is extremely painful. Bumblefoot is especially prevalent in environments with hard perches. Poor hygiene, such as wet litter or manure, heightens the risk of developing bumblefoot syndrome. ^[61] . This condition is more common in free-range barns with hard flooring and limited vegetation access.

A study conducted on 47 farms in Belgium found that an alarming 71% of laying hens suffered from foot problems over a 60-week period. The most prevalent issue was hyperkeratosis, affecting 42% of the hens. ^[53] .

Cloaca prolapse

When laying eggs, the final section of the oviduct turns inside out and temporarily extends outside the body, enabling a clean egg to be laid. However, sometimes the oviduct fails to retract properly and stays outside the cloaca. This issue is particularly prevalent in older animals, as the muscles responsible for retraction may have weakened due to frequent egg-laying sessions. ^[62] .

A noticeable chicken attracts the attention of other chickens, leading to a worsening situation.

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