Genetic variation in pure lines and crosses of large-bodied turkey lines. 1. Body weight, walking ability, and body measurements of live birds.

An experimental line of turkeys selected for increased BW (F) was reciprocally crossed with sire lines (designated A and B) from each of two major commercial breeders in order to study the inheritance of growth traits. All genetic groups were grown intermingled in confinement with the sexes reared in different houses. Traits measured included BW at 8, 16, and 20 wk of age; shank length, width, and depth; breast width; and walking ability scores at 16 wk of age. The F line had a different growth pattern than the two commercial sire lines. The F line had higher (males) or similar (females) BW in comparison to Line A at 8 wk of age, but by 16 wk of age, Line A was heavier than Line F in both sexes. The difference in BW between the F and A lines increased from 16 to 20 wk of age. Lines F and B did not differ in BW at 8 wk of age, but at 16 and 20 wk of age, Line B birds were heavier than those of F line. Reciprocal effects, a measure of sex linkage and maternal effects, were noted only for breast width of females in crosses of Lines A and F and for shank width and depth of males and 8-wk BW and shank depth of females in crosses of Lines B and F. Heterosis was an important source of variation in BW for males from both crosses. The percentage heterosis at the various ages ranged from 3.1 to 7.5. For females, heterosis (range = 2.6 to 4.9%) was only significant at younger ages (8 wk for the crosses of the A and F lines and 8 and 16 wk for the crosses of the B and F lines). No heterosis for breast width was observed in either cross. Heterosis in walking ability scores was significant only for males from the crosses of Lines B and F. The presence of heterosis was inconsistent for shank measurements.