Morphodynamics of Embryonic Development of Skeletal Musculature of Broiler and Layer Chickens

Eggs of broiler (Ross 308) and layer (Hy-Line Brown) chicken hybrids were incubated and tissue samples from the leg muscle (m. biceps femoris) and breast muscle (m. pectoralis profundus) were taken on embryonic days 9, 12, 15, 18 and 20, as well as on the first day post hatching. Histological preparations were made from the samples and the diameter of muscle cells, the volume density of connective tissue of muscles, and the nucleocytoplasmic ratio of muscle cells were recorded. Comparison of the diameter of muscle cells of leg muscle and the breast muscle between broiler and layer chicken during the period of late incubation and day 1 post hatching showed the diameter of the examined muscle cells was greater in layers, while the nucleocytoplasmic ratio of muscle cells was higher in broilers. No differences were established between these two strains in the volume density of connective tissue in both muscles examined. Such results are explained by the prolonged proliferation of myoblasts and delayed differentiation of muscle cells in broilers, which leads to a greater development of the skeletal musculature during the postnatal period. These processes in the embryonic period of development are the cause of differences in the morphodynamics of embryonic development of the skeletal musculature between broilers and layers presented in this paper.