| Popis: |
Body growth, muscle growth, bone growth, and measurements of muscle fiber area and fiber number were made in a line of Japanese quail (Coturnix coturnix japonica) selected for high 4 week body weight for 100 generations (line PP), in the control line from which they were derived (line CC), and in genetically equivalent reciprocal crosses (PC and CP) that develop in eggs that differ greatly in weight. There was no difference in body weight or weight of the P. superficialis of newly hatched CC or PC quail. Weights of PP and CP were equal to each other but greater than those of CC and PC. Body and muscle weights of the crosses were equal by 3 to 4 weeks of age. The number of fibers in the Semimembranosus muscle was lowest in CC quail, intermediate in PC and CP quail, and greatest in PP. Cross-sectional area of Semimembranosus fibers from 7 day old CC and PC were equal to each other and smaller than those of PP or CP quail. By 29 days of age, fibers in CC were smallest, those in PC and CP were intermediate and smaller than those of PP quail. At 7 days, the cross-sectional area of P. superficialis fibers of CP quail was greater than those of the other genotypes, but by 14 days and after fiber area was directly related to the bird's genetic potential for growth. These studies show that fiber hyperplasia is genetically determined whereas fiber hypertrophy in early life is primarily dependent on the dam's genotype and egg environment. |
