In recent decades, poultry meat and egg production from individual birds in commercial flocks of broilers and layers has increased enormously, largely owing to genetic selection in the nucleus breeding flocks of poultry breeding companies and the rapid transfer of these gains to commercial crossbred progeny. With increasing urbanization, the contribution of commercial breeds to overall poultry meat and egg consumption is growing evermore rapidly, while indigenous breeds continue to make large contributions to poultry meat and egg consumption in the rural regions of most countries.

In most tropical countries, the main physiological impediment to good production from commercial poultry is the birds' lack of heat tolerance under high ambient temperatures. Heat tolerance can be increased by incorporating major genes that reduce feather cover on the body. However, high-producing lines that express these genes are not generally available.

Various approaches have been used to improve the performance of adapted indigenous stock, including cross-breeding and upgrading through back-crossing with commercial breeds, and within-line selection. All these approaches, however, have limitations: cross-breeding and back-crossing require the keeping of separate populations, and result in a loss of broodiness in the offspring and may reduce the consumer appeal of the eggs and meat; further within-line selection is successful only on a relatively large scale and under well-controlled conditions.

The indigenous breeds used in family poultry farming in the rural areas of developing countries contribute greatly to the genetic diversity of the world's poultry populations. There are therefore significant concerns that the replacement of indigenous breeds with commercial strains of poultry could pose a real threat to the poultry genetic resources.