Skeletal Muscle Characteristics of Broiler Chickens under Modified Incubation Factors

Four groups of broiler chicken hybrid ( Ross 308) eggs were incubated under different temperature and light conditions to assess the effects of both variables on musculature development. During the incubation, the first group was the control and the eggs were incubated at a temperature of 37.8 °C without light, the second group was exposed to increased temperature, while the third group was exposed to monochromatic green light. The fourth group of eggs was incubated under simultaneously changed temperature (according to the regime of the second group) and light (according to the regime of the third group) conditions. Tissue samples from the breast muscle ( M. pectoralis superficialis) were taken on embryonic days 9, 12, 15, 19 and 20, as well as on days 1, 3, 7, 14, 21 and 42 after hatching. Histological preparations were used to assess muscle cell diameter, connective tissue volume density, and the nucleocytoplasmic ratio of muscle cells. Our findings indicate that thermal and light manipulations during incubation increase diameter and decrease nucleocytoplasmic ratio in postnatal skeletal muscle cells. No differences were found among groups with regard to connective tissue volume density. These results can be explained by the influence of thermal and light manipulations during incubation on prolonged myoblast proliferation, as well as on the greater postnatal development of skeletal muscle cells.