The chicken is a descendant of the Southeast Asian red jungle fowl, first domesticated in India around 2000 B.C. After humans have kept them now for thousands of years, selection and breeding has led to chickens in many colors, sizes and shapes.
Commercial hens usually begin laying eggs at 16–21 weeks of age. Egg production gradually declines soon after. Thus, in many countries, by approximately 72 weeks of age, flocks are considered economically unviable. They are slaughtered after approximately 12 months of egg production. In contrasts, chickens will naturally live for 6 or more years.
Today, a factory-farmed chicken, called ‘broiler chicken’, is typically slaughtered for meat at an age around 45 days (6 to 7 weeks). Their feed consists primarily of corn and soybean meal with the addition of essential vitamins and minerals. Hormones or steroids are not allowed.