The Chicken or The Egg: The Origin of Today’s Domestic Meat Chicken
Recent genetic studies suggest that chickens were initially domesticated about 8000 years ago from a subspecies of Red Jungle Fowl (Gallus gallus) found today in southwestern China, northern Thailand and Myanmar. By about 6000 BC the Chinese were recorded as using chickens as a source of food. Following their initial domestication, chickens were spread across Southeast and South Asia.
Domesticated chickens appeared in India by about 2000 BC and are thought to have spread from there to Africa soon after. This spread continued, mainly through the Iron Age, and chickens were taken through Russia across Europe. They also spread from China to Japan and Korea in about 300 BC – 300 AD.
However, today’s meat chicken looks quite different from its wild ancestor – and quite different from modern laying chickens, which are bred specifically for egg production.
Selective Breeding: Selecting the Best to Produce the Next Generation
Selective breeding is the foundation of agriculture as we know it today. All agricultural endeavours fundamentally revolve around selective breeding. Dairy cows produce more milk, wheat crops are more abundant, corn cobs are juicier, sugar cane has a greater sugar content, sheep grow finer and more wool etc, all due, to some extent, to selective breeding. Without selective breeding, crops and livestock would be much more disease prone and far less productive. The basic concept of selective breeding is quite simple. It consists of selecting those plants or animals which show the desirable characteristics as the parents for the next generation in the breeding program and doing so repeatedly over many generations.
A good illustration of what selective breeding can achieve is the substantial difference between today’s meat chicken and a chicken bred for table eggs (a so-called layer hen).
Selective breeding is particularly effective in situations where the reproductive cycle is short. That is particularly true of chickens. Breeding chickens reach sexual maturity and start producing eggs at about 20-25 weeks of age. It then takes only three weeks for those eggs to hatch and produce the next generation. If you start with a female chick, for example a meat Great Grandparent hen, she will produce at least 64 chicks in a year, 32 of which will be female. These 32 (Grandparent) hens will each produce at least 80 chicks, 40 of which will be female (Parent hens), and each of these will go on themselves to produce 140 meat chickens. In this way, one Great Grandparent hen will be responsible for passing on her genetics to at least 182,000 meat chickens, within a period of just 2.5 years.
Modern breeding efforts aim for a well-rounded breed that exhibits a range of important characteristics, with good growth being but one of a very broad spectrum of traits prized and selected for.
It is also important to acknowledge that many other factors such as nutrition, animal and plant health, animal husbandry and farming techniques also contribute substantially to successful and sustainable farming.
How the chickens that are used to produce meat in Australia are bred and how so many of them can be produced is summarised in the diagram.