Welfare of broiler chickens

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The breeding and raising of broiler chickens has created health and animal welfare issues, such as cardiovascular and skeletal dysfunction.

Contents

Meat birds

One-day-old chicks arriving to be unpacked and placed in shed Broiler chicks.jpg
One-day-old chicks arriving to be unpacked and placed in shed
Young birds being reared in a closed broiler house Ayam.jpg
Young birds being reared in a closed broiler house

Artificial selection has led to a great increase in the speed with which broilers develop and reach slaughter-weight. The time required to reach 1.5 kg (3 lb 5 oz) live-weight decreased from 120 days to 30 days between 1925 and 2005. Selection for fast early growth-rate, and feeding and management procedures to support such growth, have led to various welfare problems in modern broiler strains. [1] Welfare of broilers is of particular concern given the large number of individuals that are produced; for example, the U.S. in 2011 produced approximately 9 billion broiler chickens. [2]

Cardiovascular dysfunction

Selection and husbandry for very fast growth means there is a genetically induced mismatch between the energy-supplying organs of the broiler and its energy-consuming organs. [3] Rapid growth can lead to metabolic disorders such as sudden death syndrome (SDS) and ascites. [1]

SDS is an acute heart failure disease that affects mainly male fast-growing broilers which appear to be in good condition. Affected birds suddenly start to flap their wings, lose their balance, sometimes cry out and then fall on their backs or sides and die, usually all within a minute. In 1993, U.K. broiler producers reported an incidence of 0.8%. In 2000, SDS has a death rate of 0.1–3% in Europe. [3]

Ascites is characterised by hypertrophy and dilatation of the heart, changes in liver function, pulmonary insufficiency, hypoxaemia and accumulation of large amounts of fluid in the abdominal cavity. Ascites develops gradually and the birds suffer for an extended period before they die. In the UK, up to 19 million broilers die in their sheds from heart failure each year. [4]

Skeletal dysfunction

Breeding for increased breast muscle means that the broilers' centre of gravity has moved forward and their breasts are broader compared with their ancestors, which affects the way they walk and puts additional stresses on their hips and legs. [3] There is a high frequency of skeletal problems in broilers, mainly in the locomotory system, including varus and valgus deformities, osteodystrophy, dyschondroplasia and femoral head necrosis. [1] These leg abnormalities impair the locomotor abilities of the birds, and lame birds spend more time lying and sleeping. [5] The behavioural activities of broilers decrease rapidly from 14 days of age onwards. [6] Reduced locomotion also decreases ossification of the bones and results in skeletal abnormalities; these are reduced when broilers have been exercised under experimental conditions. [1]

Most broilers find walking painful, as indicated by studies using analgesic and anti-inflammatory drugs. In one experiment, healthy birds took 11 seconds to negotiate an obstacle course, whereas lame birds took 34 seconds. After the birds had been treated with carprofen, there was no effect on the speed of the healthy birds, however, the lame birds now took only 18 seconds to negotiate the course, indicating that the pain of lameness is relieved by the drug. [7] In self-selection experiments, lame birds select more drugged feed than non-lame birds [8] leading to the suggestion that leg problems in broilers are painful.

Several research groups have developed "gait scores" (GS) to objectively rank the walking ability and lameness of broilers. In one example of these scales, GS=0 indicates normal walking ability, GS=3 indicates an obvious gait abnormality which affects the bird's ability to move about and GS=5 indicates a bird that cannot walk at all. GS=5 birds tried to use their wings to help them walking, or crawled along on their shanks. In one study, almost 26% of the birds examined were rated as GS=3 or above and can therefore be considered to have suffered from painful lameness. [3]

Compassion in World Farming wrote on the incidence of leg problems in broilers:

...there is evidence that, far from improving, leg problems may have deteriorated further during the 1990s. Large and representative surveys of commercial broiler flocks in Denmark (1999) and Sweden (2002) found that in Denmark, 75% of the chickens had some walking abnormality and 30.1% were very lame (gait score greater than 2). In Sweden, over 72% of the chickens had some walking abnormality and around 20% were very lame. 36.9% of the chickens surveyed in Denmark and around half (46.4% and 52.6%, depending on strain) of the chickens surveyed in Sweden had leg deformities (varus/valgus). 57% of the chickens surveyed in Denmark and around half of the chickens surveyed in Sweden showed some evidence of tibial dychondroplasia (Sanotra, Berg and Lund, 2003). [3]

The video recordings below are examples of broilers attempting to walk with increasing levels of gait abnormalities and therefore increasing gait scores.

Integument lesions

Sitting and lying behaviours in fast growing strains increase with age from 75% in the first seven days to 90% at 35 days of age. This increased inactivity is linked with an increase in dermatitis caused by a greater amount of time in contact with ammonia in the litter. This contact dermatitis is characterised by hyperkeratosis and necrosis of the epidermis at the affected sites; it can take forms such as hock burns, breast blisters and foot pad lesions. [1]

Stocking density

Broilers in a rearing shed indicating the high stocking densities used Ptichnik.JPG
Broilers in a rearing shed indicating the high stocking densities used

Broilers are usually kept at high stocking densities which vary considerably between countries. Typical stocking densities in Europe range between about 22–42 kg/m2 (5–9 lb/sq ft) or between about 11 to 25 birds per square metre (1.0 to 2.3/sq ft). [3] There is a reduction of feed intake and reduced growth rate when stocking density exceeds approximately 30 kg/m2 (6 lb/sq ft) under deep litter conditions. The reduced growth rate is likely due to a reduced capacity to lose heat generated by metabolism. Higher stocking densities are associated with increased dermatitis including foot pad lesions, breast blisters and soiled plumage. [1] In a large-scale experiment with commercial farms, it was shown that the management conditions (litter quality, temperature and humidity) were more important than stocking density. [9]

Ocular dysfunction

In attempts to improve or maintain fast growth, broilers are kept under a range of lighting conditions. These include continuous light (fluorescent and incandescent), continuous darkness, or under dim light; chickens kept under these light conditions develop eye abnormalities such as macrophthalmos, avian glaucoma, ocular enlargement and shallow anterior chambers. [10]

Ammonia

The litter in broiler pens can become highly polluted from the nitrogenous feces of the birds and produce ammonia. Ammonia has been shown to cause increased susceptibility to disease and other health-related problems such as Newcastle disease, airsaculitis and keratoconjunctivitis. The respiratory epithelium in birds is damaged by ammonia concentrations in the air exceeding 75 parts per million (ppm). Ammonia concentrations at 25 to 50 ppm induce eye lesions in broiler chicks after seven days of exposure.[ citation needed ]

Catching and transport

Once the broilers have reached the target live-weight, they are caught, usually by hand, and packed live into crates for transport to the slaughterhouse. They are usually deprived of food and water for several hours before catching until slaughter. The process of catching, loading, transport and unloading causes serious stress, injury and even death to a large number of broilers.

The number of broilers that died in the EU in 2005 during the process of catching, packing and transport was estimated to be as high as 18 to 35 million. In the UK, of broilers that were found to be 'dead on arrival' at the slaughterhouse in 2005, it was estimated that up to 40% may have died from thermal stress or suffocation due to crowding on the transporter. [3]

Slaughter is done by hanging the birds fully conscious by their feet upside-down in shackles on a moving chain, stunning them by automatically immersing them in an electrified water bath and exsanguination by cutting their throats.

Some research indicates that chickens might be more intelligent than previously supposed, which "raises questions about how they are treated". A possible 10 year life span has been shortened to six weeks for broilers. [11]

Mortality rates

According to historical records, broiler mortality rates in the U.S. have decreased from 18% in 1925 to 3.7% in 2012, but have increased since 2013 to reach 5% in 2018. [12]

One indication of the effect of broilers' rapid growth rate on welfare is a comparison of the usual mortality rate for standard broiler chickens (1% per week) with that for slower-growing broiler chickens (0.25% per week) and with young laying hens (0.14% per week); the mortality rate of the fast-growing broilers is seven times the rate of laying hens (the same subspecies) of the same age. [3]

Parent birds

Meat broilers are usually slaughtered at approximately 35 to 49 days of age, well before they become sexually reproductive at 5 to 6 months of age. However, the bird's parents, often called "broiler-breeders", must live to maturity and beyond so they can be used for breeding. As a consequence, they have additional welfare concerns.

Meat broilers have been artificially selected for an extremely high feeding motivation, but are not usually feed-restricted, as this would delay the time taken for them to reach slaughter-weight. Broiler-breeders have the same highly increased feeding motivation, but must be feed-restricted to prevent them becoming overweight with all its concomitant life-threatening problems. An experiment on broilers' food intake found that 20% of birds allowed to eat as much as they wanted either died or had to be killed because of severe illness between 11 and 20 weeks of age – either they became so lame they could not stand, or they developed cardiovascular problems. [3]

Broiler breeders fed on commercial rations eat only a quarter to a half as much as they would with free access to food. They are highly motivated to eat at all times, presumably leading to chronic frustration of feeding. [13]

Because broiler breeders live to adulthood, they might show feather pecking or other injurious pecking behaviour. To avoid this, they might be beak trimmed which can lead to acute or chronic pain.

Related Research Articles

<span class="mw-page-title-main">Poultry</span> Domesticated birds kept by humans for their eggs, meat, or feathers

Poultry are domesticated birds kept by humans for the purpose of harvesting useful animal products such as meat, eggs or feathers. The practice of raising poultry is known as poultry farming. These birds are most typically members of the superorder Galloanserae (fowl), especially the order Galliformes. The term also includes waterfowls of the family Anatidae but does not include wild birds hunted for food known as game or quarry.

<span class="mw-page-title-main">Debeaking</span> Trimming of a birds beak, usually performed on domesticated birds

Debeaking, beak trimming, or beak conditioning is the partial removal of the beak of poultry, especially layer hens and turkeys although it may also be performed on quail and ducks. Most commonly, the beak is shortened permanently, although regrowth can occur. The trimmed lower beak is somewhat longer than the upper beak. A similar but separate practice, usually performed by an avian veterinarian or an experienced birdkeeper, involves clipping, filing or sanding the beaks of captive birds for health purposes – in order to correct or temporarily to alleviate overgrowths or deformities and better allow the bird to go about its normal feeding and preening activities. Amongst raptor-keepers, this practice is commonly known as "coping".

<span class="mw-page-title-main">Domestic turkey</span> Species of bird

The domestic turkey is a large fowl, one of the two species in the genus Meleagris and the same species as the wild turkey. Although turkey domestication was thought to have occurred in central Mesoamerica at least 2,000 years ago, recent research suggests a possible second domestication event in the area that is now the southwestern United States between 200 BC and 500 AD. However, all of the main domestic turkey varieties today descend from the turkey raised in central Mexico that was subsequently imported into Europe by the Spanish in the 16th century.

<span class="mw-page-title-main">Broiler</span> Chicken bred for meat

Breed broiler is any chicken that is bred and raised specifically for meat production. Most commercial broilers reach slaughter weight between four and six weeks of age, although slower growing breeds reach slaughter weight at approximately 14 weeks of age. Typical broilers have white feathers and yellowish skin. Broiler or sometimes broiler-fryer is also used sometimes to refer specifically to younger chickens under 2.0 kilograms, as compared with the larger roasters.

<span class="mw-page-title-main">Free range</span> Method of farming where animals can roam freely outdoors

Free range denotes a method of farming husbandry where the animals, for at least part of the day, can roam freely outdoors, rather than being confined in an enclosure for 24 hours each day. On many farms, the outdoors ranging area is fenced, thereby technically making this an enclosure, however, free range systems usually offer the opportunity for the extensive locomotion and sunlight that is otherwise prevented by indoor housing systems. Free range may apply to meat, eggs or dairy farming.

Tibial dyschondroplasia (TD) is a metabolic disease of young poultry that affects the growth of bone and cartilage. Often occurs in broilers and other poultry which have been bred for fast growth rates. The tibial cartilage does not mature enough to ossify. This leaves the growth plate prone to fracture, infection, and deformed bone development.

Panosteitis, sometimes shortened to pano among breeders, is an occasionally seen long bone condition in large breed dogs. It manifests with sudden, unexplained pain and lameness that may shift from leg to leg, usually between 5 and 14 months of age, earning the nickname "growing pains. " Signs such as fever, weight loss, anorexia, and lethargy can also be seen. The cause is unknown, but genetics, stress, infection, metabolism, or an autoimmune component may be factors. It has also been suggested that rapid growth and high-protein food are involved in the pathogenesis. Whole blood analysis may show an elevated white blood cell count; this finding lends support to the theory that panosteitis is due to an infection.

<span class="mw-page-title-main">Chicken as food</span> Type of meat

Chicken is the most common type of poultry in the world. Owing to the relative ease and low cost of raising chickens—in comparison to mammals such as cattle or hogs—chicken meat and chicken eggs have become prevalent in numerous cuisines.

<span class="mw-page-title-main">Poultry litter</span> Mixture of chickens excretions, feed, feathers and bedding

In agriculture, poultry litter or broiler litter is a mixture of poultry excreta, spilled feed, feathers, and material used as bedding in poultry operations. This term is also used to refer to unused bedding materials. Poultry litter is used in confinement buildings used for raising broilers, turkeys and other birds. Common bedding materials include wood shavings, sawdust, peanut hulls, shredded sugar cane, straw, and other dry, absorbent, low-cost organic materials. Sand is also occasionally used as bedding. The bedding materials help absorb moisture, limiting the production of ammonia and harmful pathogens. The materials used for bedding can also have a significant impact on carcass quality and bird performance.

<span class="mw-page-title-main">Perdue Farms</span> American meat processing company

Perdue Farms is the parent company of Perdue Foods and Perdue AgriBusiness, based in Salisbury, Maryland. Perdue Foods is a major chicken, turkey, and pork processing company in the United States. Perdue AgriBusiness ranks among the top United States grain companies. Perdue Farms has 2021 annual sales of $8 billion.

<span class="mw-page-title-main">Intensive animal farming</span> Branch of agriculture

Intensive animal farming, industrial livestock production, and macro-farms, also known as factory farming, is a type of intensive agriculture, specifically an approach to animal husbandry designed to maximize production while minimizing costs. To achieve this, agribusinesses keep livestock such as cattle, poultry, and fish at high stocking densities, at large scale, and using modern machinery, biotechnology, and global trade. The main products of this industry are meat, milk and eggs for human consumption. There are issues regarding whether intensive animal farming is sustainable in the social long-run given its costs in resources. Analysts also raise issues about its ethics.

<span class="mw-page-title-main">Poultry farming</span> Part of animal husbandry

Poultry farming is the form of animal husbandry which raises domesticated birds such as chickens, ducks, turkeys and geese to produce meat or eggs for food. Poultry – mostly chickens – are farmed in great numbers. More than 60 billion chickens are killed for consumption annually. Chickens raised for eggs are known as layers, while chickens raised for meat are called broilers.

Pale, soft, exudative meat, or PSE meat, describes a carcass quality condition known to occur in pork, beef, and poultry. It is characterized by an abnormal color, consistency, and water holding capacity, making the meat dry and unattractive to consumers. The condition is believed to be caused by abnormal muscle metabolism following slaughter, due to an altered rate of glycolysis and a low pH within the muscle fibers. A mutation point in the ryanodine receptor gene (RYR1) in pork, associated to stress levels prior to slaughter are known to increase the incidence of PSE meat. Although the term "soft" may look positive, it refers to raw meat. When cooked, there is higher cook loss and the final product is hard, not juicy.

<span class="mw-page-title-main">Naked Neck</span> Breed of chicken

The Naked Neck is a breed of chicken that is naturally devoid of feathers on its neck and vent. The breed is also called the Transylvanian Naked Neck, as well as the Turken. The name "Turken" arose from the mistaken idea that the bird was a hybrid of a chicken and the domestic turkey. Naked Necks are fairly common in Europe today, but are rare in North America and very common in South America. The trait for a naked neck is a dominant one controlled by one gene and is fairly easy to introduce into other breeds, however these are hybrids rather than true Naked Necks, which is a breed recognized by the American Poultry Association since 1965, it was introduced in Britain in the 1920s. There are other breeds of naked necked chicken, such as the French naked neck, which is often confused with the Transylvanian, and the naked necked gamefowl.

<span class="mw-page-title-main">Deep litter</span>

Deep litter is an animal housing system, based on the repeated spreading of straw or sawdust material in indoor booths. An initial layer of litter is spread for the animals to use for bedding material and to defecate in, and as the litter is soiled, new layers of litter are continuously added by the farmer. In this fashion, a deep litter bedding can build up to depths of 1–2 meters. "The usual procedure for built-up floor litter is to start with about 4 inches (100 mm) of fine litter material with additions of 1 to 2 inches later as needed without removal of the old. A depth of 6 to 12 inches is maintained by partial removals from time to time." Many consider this to be a natural means to disposing of animal feces. "The deep litter cultivation is a modern ecological breeding technique based on decomposing feces by microbiological methods, a post processing method for poultry Manure."

<span class="mw-page-title-main">Poultry farming in the United States</span>

Poultry farming is a part of the United States's agricultural economy.

<span class="mw-page-title-main">Feather pecking</span> When one bird repeatedly pecks at the feathers of another

Feather pecking is a behavioural problem that occurs most frequently amongst domestic hens reared for egg production, although it does occur in other poultry such as pheasants, turkeys, ducks, broiler chickens and is sometimes seen in farmed ostriches. Feather pecking occurs when one bird repeatedly pecks at the feathers of another. The levels of severity may be recognized as mild and severe. Gentle feather pecking is considered to be a normal investigatory behaviour where the feathers of the recipient are hardly disturbed and therefore does not represent a problem. In severe feather pecking, however, the feathers of the recipient are grasped, pulled at and sometimes removed. This is painful for the receiving bird and can lead to trauma of the skin or bleeding, which in turn can lead to cannibalism and death.

<span class="mw-page-title-main">Dwarfism in chickens</span>

Dwarfism in chickens is an inherited condition found in chickens consisting of a significant delayed growth, resulting in adult individuals with a distinctive small size in comparison with normal specimens of the same breed or population.

<span class="mw-page-title-main">Broiler industry</span> Process by which broiler chickens are reared and prepared for meat consumption

The broiler industry is the process by which broiler chickens are reared and prepared for meat consumption. Worldwide, in 2005 production was 71,851,000 tonnes. From 1985 to 2005, the broiler industry grew by 158%.

<span class="mw-page-title-main">Feed manufacturing</span>

Feed manufacturing refers to the process of producing animal feed from raw agricultural products. Fodder produced by manufacturing is formulated to meet specific animal nutrition requirements for different species of animals at different life stages. According to the American Feed Industry Association (AFIA), there are four basic steps:

  1. Receive raw ingredients: Feed mills receive raw ingredients from suppliers. Upon arrival, the ingredients are weighed, tested and analyzed for various nutrients and to ensure their quality and safety.
  2. Create a formula: Nutritionists work side by side with scientists to formulate nutritionally sound and balanced diets for livestock, poultry, aquaculture and pets. This is a complex process, as every species has different nutritional requirements.
  3. Mix ingredients: Once the formula is determined, the mill mixes the ingredients to create a finished product.
  4. Package and label: Manufacturers determine the best way to ship the product. If it is prepared for retail, it will be "bagged and tagged," or placed into a bag with a label that includes the product's purpose, ingredients and instructions. If the product is prepared for commercial use, it will be shipped in bulk.

References

  1. 1 2 3 4 5 6 Bessei W (2006). "Welfare of broilers: A review". World's Poultry Science Journal. 62 (3): 455–466. doi:10.1017/s0043933906001085. S2CID   86638983.
  2. ↑ "Broiler chicken key facts". National Chicken Council. Retrieved November 10, 2014.
  3. 1 2 3 4 5 6 7 8 9 Turner, J.; Garcés L. and Smith, W. (2005). "The Welfare of Broiler Chickens in the European Union" (PDF). Compassion in World Farming Trust. Retrieved November 16, 2014.
  4. ↑ "Compassion in World Farming – Meat chickens – Welfare issues". CIWF.org.uk. Archived from the original on 2013-10-23. Retrieved 2011-08-26.
  5. ↑ Vestergaard KS, Sonatra GS (1999). "Relationships between leg disorders and changes in behaviour of broiler chickens". Veterinary Record. 144 (8): 205–209. doi:10.1136/vr.144.8.205. PMID   10097343. S2CID   7739290.
  6. ↑ Reiter K, Bessei W (1995). "Influence of running on leg weakness of slow and fast growing broilers". Proceedings 29th International Congress ISAE, Exeter, U.K., 3–5 August: 211–213.
  7. ↑ McGeown D, Danbury TC, Waterman-Pearson AE, Kestin SC (1999). "Effect of carprofen on lameness in broiler chickens". Veterinary Record. 144 (24): 668–671. doi:10.1136/vr.144.24.668. PMID   10404606. S2CID   1765766.
  8. ↑ Danbury TC, Weeks CA, Chambers JP, Waterman-Pearson AE, Kestin SC (2000). "Self-selection of the analgesic drug carprofen by lame broiler chickens". Veterinary Record. 146 (11): 307–311. doi:10.1136/vr.146.11.307. PMID   10766114. S2CID   35062797.
  9. ↑ Dawkins MS, Donelly S, Jones TA (2004). "Chicken welfare is influenced more by housing conditions than by stocking density". Nature. 427 (6972): 342–344. Bibcode:2004Natur.427..342S. doi:10.1038/nature02226. PMID   14737165. S2CID   4354183.
  10. ↑ Lauber JK, Kinnear A (1979). "Eye enlargement in birds induced by dim light". Canadian Journal of Ophthalmology. 14 (4): 265–269. PMID   550921.
  11. ↑ Smith CL, Zielinski SL (February 2014). "Brainy Bird". Scientific American. 310 (2): 60–65. Bibcode:2014SciAm.310b..60S. doi:10.1038/scientificamerican0214-60. PMID   24640333.
  12. ↑ "U.S. Broiler Performance". National Chicken Council. Retrieved August 1, 2019.
  13. ↑ Savory CJ, Maros K, Rutter SM (1993). "Assessment of hunger in growing broiler breeders in relation to a commercial restricted feeding programme". Animal Welfare. 2 (2): 131–152. doi:10.1017/S0962728600015669. S2CID   196655031.
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