Tenderness
While all chickens (and turkeys) are similar in most respects, differences exist in tenderness that greatly impact the ultimate use of the meat. Broiler chickens are hatched, grown, and processed by 7 weeks of age because their sole function is meat production.
The chickens (laying hens) that lay table eggs for human consumption and the other chickens (broiler breeders) that lay eggs to be hatched for broiler production (these eggs are not the same) are generally processed after their egg production abilities are exhausted (>1 year of age).
The meat from these older birds is much tougher than broiler meat because as an animal matures, the connective tissues holding the muscle together become very heat resistant and no longer break down easily during cooking. As a result, meat from these older birds is used in products receiving extreme heat treatments such as the retorting of canned soups or the prolonged cooking of stewing hens. These extreme heat treatments are sufficient to overcome the heat resistance of the connective tissue in older animals.