Abstract
An experimental line (F) of turkeys 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. The birds were grown, sexes separate, in confinement in different houses. Traits measured included body weight at 8, 16, and 20 weeks of age, and shank length, shank width, shank depth, and breast width at 16 weeks of age. In addition to the above measurements, walking ability score was recorded for each bird at 16 weeks of age. Each bird was given a score of 1 to 5 with 1 representing birds whose legs did not have any defect and had no difficulty walking and 5 indicating birds whose legs exhibited extreme lateral deviations and had great difficulty walking. Ratings of 2, 3, and 4 represented intermediate values.
The F line had a different growth pattern than the two commercial sire lines. The F line had superior (males) or equivalent (females) body weights in comparison to Line A at 8 weeks of age but by 16 weeks of age Line A was heavier than Line F in both sexes. The difference between the F and A lines increased from 16 to 20 weeks of age. The F and B lines did not differ in body weight at 8 weeks of age but at 16 and 20 weeks of age Line B was heavier than the F line in both sexes.
Reciprocal effects, a measure of sex linkage or maternal effects, were noted only for breast width of females in crosses of Lines A and F and for shank width and shank depth of males and 8-week body weight and shank depth of females in crosses of Lines B and F. Heterosis was an important source of variation in body weight of 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 weeks for the crosses of the A and F lines and 8 and 16 weeks 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 of the crosses of Lines B and F. The presence of heterosis was inconsistent for shank measurements.