Poultry farming is a type of animal husbandry in which domesticated birds such as chickens, ducks, turkeys, and geese are raised to provide meat or eggs for human use. It dates back to the agrarian period. Poultry, mostly chickens, are grown in large numbers. Every year, more than 60 billion chickens are slaughtered for human consumption. Layers are birds grown for eggs, whereas broilers are chickens raised for meat.