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 reciproca lly crossed with sire lines (designated A and B) from each of two major com mercial breeders in order to study the inheritance of growth traits. All ge netic groups were grown intermingled in confinement with the sexes reared i n 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 a t 16 wk of age. The F line had a different growth pattern than the two commercial sire line s. The F line had higher (males) or similar (females) BW in comparison to L ine A at 8 wk of age, but by 16 wk of age, Line A was heavier than Line F i n 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 not ed only for breast width of females in crosses of Lines A and F and for sha nk width and depth of males and 8-wk BW and shank depth of females in cross es of Lines B and F. Heterosis was an important source of variation in BW f or males from both crosses. The percentage heterosis at the various ages ra nged 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 wa s significant only for males from the crosses of Lines B and F. The presenc e of heterosis was inconsistent for shank measurements.