Domestic chickens appeared more than 8 000 years ago in Southeast Asia and were introduced to the rest of the world by sailors and traders. Today, they are by far the most important poultry species in the world.

High-yielding commercial breeds of chickens have been developed in recent decades to meet growing global demand for animal-source foods. These chickens are bred specifically either for meat or egg production and require intensive nutritional and health management to express their genetic potential. They are widely available all over the world, and are used by most large-scale companies.

Dual-purpose indigenous breeds are typically kept in rural and peri-urban areas and would be considered inefficient in commercial farms. But despite their lower productivity, they are ideal for low-input poultry systems. They are well adapted to their environments, resistant to diseases, can scavenge for food, and are able to avoid predators as they are agile and fast, with the colour and patterns of their feathers providing natural camouflage. Hens have a strong instinct for brooding, which enables them to hatch their own eggs and care for the vulnerable chicks.

Various crossbred chickens are also available in some regions. Their meat and egg production is relatively good under moderate climatic and nutritional management conditions.