Growth and muscle characteristics of a growth selected line of Japanese quail (Coturnix coturnix japonica), a control line and reciprocal crosses between them

Body growth, muscle growth, bone growth, and measurements of muscle fiber a rea and fiber number were made in a line of Japanese quail (Coturnix coturn ix 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 ge netically equivalent reciprocal crosses (PC and CP) that develop in eggs th at differ greatly in weight. There was no difference in body weight or weig ht of the P. superficialis of newly hatched CC or PC quail. Weights of PP a nd CP were equal to each other but greater than those of CC and PC. Body an d muscle weights of the crosses were equal by 3 to 4 weeks of age. The numb er of fibers in the Semimembranosus muscle was lowest in CC quail, intermed iate in PC and CP quail, and greatest in PP. Cross-sectional area of Semime mbranosus fibers from 7 day old CC and PC were equal to each other and smal ler than those of PP or CP quail. By 29 days of age, fibers in CC were smal lest, those in PC and CP were intermediate and smaller than those of PP qua il. At 7 days, the cross-sectional area of P. superficialis fibers of CP qu ail 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 where as fiber hypertrophy in early life is primarily dependent on the dam's geno type and egg environment.