Possible maternal inheritance of breast muscle morphology in turkeys at sixteen weeks of age.

During the study of inheritance of breast muscle morphology of turkeys during embryonic development and posthatch in two experiments, interesting results were obtained at 16 wk of age. In experiment 1, an experimental line (F) selected long term for increased 16-wk BW was crossed reciprocally with a commercial sire line (B). Samples of pectoralis major muscle were obtained from three males and three females of each genetic group. The F line was reciprocally crossed with a randombred control line (RBC2) in experiment 2, and p. major muscle samples were taken from 10 males and 10 females of each genetic group. The RBC2 line was the base population for the F line. The muscle samples were obtained in a manner to avoid contraction. After fixing, the muscle samples were stained with hematoxylin and eosin to view muscle morphology. Distinct morphological types were observed in the muscle samples for the B, F, and RBC2 lines. The pectoralis major muscle from the B line was, in general, characterized by large fibers with a well-defined extracellular matrix (perimysial and endomysial spaces). Similar to the B line, representative samples of the RBC2 line had a well-defined extracellular matrix but muscle fiber size was not as large as that of the B line. Representative samples of the F line were characterized by a greatly reduced extracellular matrix with the muscle fibers not well defined. For the reciprocal crosses in both experiments, representative samples indicated the offspring had breast muscle morphology similar to that of the female parent, suggesting maternal inheritance. There was no sex effect on breast muscle morphology in either experiment. In order to study the consistency of the results, muscle morphology of representative sections of muscle were subjectively rated by four individuals. The ratings ranged from 1 (little extracellar matrix and indistinct muscle fibers) to 5 (large extracellular space and distinct muscle fibers). Ratings of 2 to 4 were intermediate to these extremes. In experiment 1, ratings of the pure B line and the F sire x B dam cross were similar and higher than that of the pure F line and B sire x F dam cross, which did not differ in average rating. The results for experiment 2 were similar to those for experiment 1 in that the average ratings of the reciprocal crosses were similar to that of the female parental line. The results from the ratings support maternal inheritance of breast muscle morphology.