The Exploitation of the Chicken The chicken (Gallus gallus domesticus) is one of the most common domesticated animals in the world, with a population of over 24 billion recorded in 2003 (Perrins 2003) meaning there are more chickens than any other bird species. Chicken keeping has been practiced for centuries and provides a source of food from both their meet and eggs. It has become an extremely productive industry, requiring skill and expert knowledge, in which methods are still developing (Broomhead 1951). Today, the majority of poultry are raised using intensive farming methods (Sherman 2002).
An alternative method is free range farming. There has been a lot of controversy between these two methods which still continues today. There are four species of wild fowl and the chicken is said to be a descendant of the red jungle fowl (Gallus gallus) in the Phasiandae family, although the origin of the chicken has been under debate for centuries. Due to the many variations in modern breeds of chicken, it is thought that all four species of fowl may have interbred to become the ancestors of the domestic poultry (Price 1969).
However, recent studies have shown that the chicken may be a hybrid of the red jungle fowl and the grey jungle fowl (G. sonneratii) due to its yellow skin which originates from the grey jungle fowl (Eriksson et al. 2008). Chickens are omnivores and feed off seeds, insects and sometimes larger mammals such as mice or lizards. They can live up to 10 years old depending on the breed (ruleworks. co. uk), although commercially farmed chickens are slaughtered much earlier than this. The males, cockerels, can usually be distinguished from the female hens by their prominent combs and colourful feathers.
They live together in flocks and, like many other poultry, they fight until a ‘pecking order’ is established (Schjelderup-Ebbe 1975). The hens will lay their eggs in the same nest and the eggs will be incubated communally. This approach is continued when raising the chicks. Hens can lay 180 – 320 eggs a year and some can lay 7 eggs per week, although most lay less than this. When an egg is fertilized, it takes around 21 days for the egg to hatch (ruleworks. co. uk). For the first two days, the newly hatched chicks will live off the egg yolk which they absorb just before they hatch.
The hen will care for the chicks until they are several weeks old. The egg laying ability of a hen begins to decline after it reaches 1 year old (Price 1969), which is why many farmed chickens are slaughtered after 1 or 2 years of age. It is thought that chicken domestication took place over 10,000 years ago in South East Asian jungles, Vietnam, Thailand and Java then spreading to China and India (Eriksson et al. 1994; Sherman 2002). In early history of man, female game birds were used as a source of meat and eggs and it was discovered that by removing some eggs from the nest, the bird would lay more eggs (Smith and Daniel 2000).
Chickens were mentioned as early as the second dynasty in Egypt and the Egyptians invented incubators built of clay brick and capable of hatching 10,000 chicks at a time (Smith and Daniel 2000). By 3000BC the chicken reached European countries such as Turkey and Greece, (Kiple and Ornelas 2000) but spread to Western Europe much later. During this time, cock fighting developed, which is a blood sport between two cockerels. Throughout these fights, the cockerel’s endured physical trauma and they sometimes ended in death. Cock fighting is now banned in most counties and has been banned in the UK since 1849 (Brown 1929).
Chicken domestication and selective breeding has developed over the years. Poultry breeding has taken place in Britain for over 2000 years and Britain now has the most diversity of fowls that any other country (Brown 1929). Chickens are bred according to their purpose. Those which are bred for meat, known as broilers, have a large body and grow rapidly. These chickens are not efficient egg layers. Chickens which are intended for egg production have a small body and are productive layers (National Research Council 1994). An example of a good layer is the Rhode Island Red as they are docile and easily managed (Price 1969).
The feeding methods differ for both broiler chickens and egg laying hens (National Research Council 1994). Selective breeding is also used to produce resistance to diseases such as fowl typhoid, bacillary diphtheria and parasitic infection (Jull 1946). Chickens are farmed all over the world. Intensive systems are most commonly used for farming chickens and are used for both meat and eggs. In 2006, it was noted that 74% of the world’s poultry meat, and 68% of eggs were produced using intensive farming techniques (Brown 2006).
The chickens are kept indoors in cramped conditions in order to restrict their movement, so more energy can be used for growth and/or egg laying. They have no access to grassland and are housed on deep litter to protect them from thieves and vermin. The farmer provides them with the best environmental conditions required for poultry production (Kekeocha 1984). Broiler chickens are usually slaughtered once they reach 6 weeks of age. This is quite young compared to free range and organic chickens, which are slaughtered at 8-12 weeks (www. ciwf. org. uk). The battery cage system is often used for egg laying hens.
These cages are usually arranged in rows and the chickens are not free to roam. They are kept in close proximity of each other and in 2003, the EU called for at least 550 cm? per hen (Appleby 2004). It was first noticed in the 1930’s that caged chickens produced more eggs (Arndt 1931) and by 1990, 75% of all commercial egg laying hens were kept in cages (North and Bell 1990). This method of rearing chickens for eggs is effective as a lot less feed is needed to produce a dozen eggs. The equipment is expensive but the labour requirements are reduced as the chickens are easier to care for (North and Bell 1990; Kekeocha 1984).
Some people oppose this method of farming as it is seen as abusive to the chickens and a few countries, such as Sweden and Switzerland have banned the cage system. The poultry houses are often overcrowded and many chickens become lame as they spend a lot of time lying down. In the UK, around 15 million chickens die in their houses each year due to heart failure caused by the extra weight they gain and overcrowding (www. ciwf. org. uk). Despite these issues, intensive farming is still widely used as it produces meat and eggs at low cost, making it difficult to reduce the number of chickens farmed this way.
An alternative way to intensive farming of chickens is extensive farming, such as free range farming. This is less commonly used but takes into account the welfare of the birds. These systems are not entirely natural but are a lot less intensive. The chickens are allowed to roam freely in grass paddocks and there can only be a maximum of 1000 birds per hectare (Thear 1990). The hens have continuous daytime access to the outdoors and are kept indoors at night. This system ensures the birds are bred in a natural-like environment, although more labour is required to care for the birds. Semi-intensive systems are also used to farm chickens.
The chickens are allowed restricted access to a certain amount of grassland but are kept in a run in which they can roam about in during the day and are shut in a house at night (Kekeocha 1984). These systems don’t give the chickens as much freedom as free range farming, but they are allowed access to grassland outdoors, unlike those farmed using the deep litter system. In order to sustain a flock, chicken farmers often use artificial incubation to incubate the eggs. The incubators provide the best conditions needed for the developing chick. The temperature is kept just below 38 degrees and the humidity at about 60%.
During the last 3 days the humidity should be increased by about 5-10%. Temperatures below 24 degrees and humidity’s below 40% can significantly decrease the hatchability of the eggs in a short space of time (Clauer 2009). Before incubation, it is important that the eggs are clean as the shells can deteriorate quickly if they become dirty. This can be achieved by regular collection of the eggs (at least once a day). It is important not to wash the eggs as this pushes germs into the pores, resulting in the invasion of micro organisms and possibly mould growth (Thompson et al. 1952).
This method of incubating chickens is viewed by some as unnatural, however it is very successful. Chickens are susceptible to a number of parasites including lice, mites, tics and roundworms. The large roundworm, Ascaridia lineata, is an internal parasite which infects the intestinal tract of the chicken. This can lead to retarded growth and sometimes result in death (Jull 1946). The distribution of A. lineata is worldwide and it is common in the United States, yet many chicken are resistant to it. This resistance was studied and it was found that the resistance of the chicken to A. ineata depended on their diet and that a plant based diet resulted in a slower growth rate and lower resistance (Ackert and Beach 1933). Parasitic infection does not tend to be a large problem when farming chickens. Chickens aren’t just used as a source of food; they are also kept as pets. Furthermore, they are used for show purposes, for example, The National Poultry Show. Most chicken breeds are used for show purposes or as pets and very few for farming (Price 1969). This is because chicken breeds used for farming require specific traits and the majority of chickens on a farm will consist of one breed.
The exterior appearance of the chicken is more important when used for shows and exhibitions. This is way of keeping chickens is mainly for pleasure or as a hobby. The chicken is a very important source of food and domestication of the chicken takes place all over the world, from large scale, intensive farming to small scale chicken keeping as pets. Humans have relied upon chickens for centuries and it is one of the most used meats in the world. This implies that it must be one of the most exploited animals in world. However, it is possible to rear chickens in a humane way in an almost atural environment, for instance, free range farming, yet this approach occurs much less often than intensive farming due to the increased costs and labour. There is a lot of controversy about the inhumane way in which chickens are farmed, but the future for chicken farming looks bleak, as it can only change if people are willing to pay extra for free range chicken products. References Ackert, J. E. and Beach, T. D. (1933) Resistance of Chickens to the Nematode, Ascaridia lineata, Affected by Dietary Supplement. Blackwell Publishing. Appleby, M. C. 2004) Chickens: Layer Housing – Encyclopedia of Animal Science. Washington, D. C. Arndt, M. (1931) Battery Brooding. 2nd ed. Broomhead, W. W. (1951) Poultry Breeding and Management. Holborn, London. Brown. E. (1929) Poultry Breeding and Production, Vol 1. London. Brown, L. R. (2006) State of the World. London. www. ciwf. org. uk (retrieved 2010) Compassion in World Farming – Chickens. Clauer, P. J. (2009) Incubating Eggs. Virginia Polytechnic Institute and State University. Eriksson, J. , Larson, G. , Gunnarsson, U. , Bed’hom, B. , Tixier-Boichard, M. , Stromstedt, L. Wright, D. , Jungerius, A. , Vereijken, A. , Randi, E. , Jensen, P. and Andersson, L. (2008) Identification of the Yellow Skin Gene Reveals a Hybrid Origin of the Domestic Chicken. Kekeocha, C. C. (1984) Poultry Production Handbook. Nairobi. Kiple, K. F. , Ornelas, K. C. (2000) The Cambridge History of Food, 2000. Cambridge University Press, vol. 1. National Research Council (1994) Nutrient Requirements of Poulty, 9th ed. Washington, D. C. North, M. O. , Bell, D. E. (1990). Commercial Chicken Production Manual. 4th ed. Perrins, C. (2003) Firefly Encyclopaedia of Birds.
Buffalo, New York. Price, C. J. (1969) Poultry Husbandry 1. www. ruleworks. co. uk (retrieved 2010) The Poultry Guide – A to Z and FAQs. Schjelderup-Ebbe, T. (1975) Contributions to the social psychology of the domestic chicken. Sherman, D. M. (2002) Tending Animals in the Global Village: A Guide to International Veterinary Medicine. Blackwell Publishing. Smith, P. , Daniel, C. (2000) The Chicken Book. University of Georgia Press. Thear, K. (1990) Free Range Poultry. Ipswich. Thompson, A. , Turnill, L. and Feltwell, R. (1952) The Complete Poultry Man. London.