Traditional free-range, slow-growing bird rearing is critical to household food security and poverty alleviation in developing countries. This study evaluated the proximate and collagen contents of the breast and thigh muscles of Red Jungle fowl (RJ), Village Chicken (VC) (slow-growing birds), and Commercial Broilers (CB) (fast-growing birds). Fifty each of the RJ, VC, and CB day-old chicks were raised under similar management. They were randomized into three groups according to breed (JV, VC, and CB), in five replicates, using cages (1.2m×1.2m×0.6m) from day old till the end of the experiment. They were fed a commercial diet and were allowed to drink water ad libitum for 120 days. Ten chickens per breed or group were serially euthanized, and their pectoralis major (breast muscle) and biceps femoris (thigh muscle) were evaluated for moisture, ash, crude protein, and collagen. The moisture in the RJ breast was lower (p≤0.05) than in the VC and CB, while it decreased (p≤0.05) with age. The crude protein in RJ and VC was higher (p≤0.05) than in CB and at an earlier age (p≤0.05) than at older ages. Collagen increased with age for all breeds evaluated; it was highest (p≤0.05) in RJ, least in CB, and higher in the thigh than in the breast. The nutrient composition differs between these birds, although they were raised under similar management. It was concluded that the age and breed of the bird influence the nutrient content of the RJ, VC, and CB muscles.