In chicken embryos, skeletal muscle development occurs from the beginning of incubation through early posthatch (Ordahl et al., 2000). Muscle progenitor cells undergo myogenic commitment, giving rise to myoblasts that first proliferate, then differentiate and fuse into muscle fibers (Naya and Olson, 1999). There are 3 types of myoblasts during embryogenesis: Embryonic myoblasts are abundant from embryonic d 3 to 7 (E3 to E7), followed by a second wave of myoblast proliferation consisting of fetal myoblasts that are abundant from E5 to E14 (Stockdale and Miller, 1987). The fetal myoblasts predominate in the embryo muscle, which undergoes marked growth through new myofiber formation and increases in diameter