INFLUENCE OF CROSSING A LINE SELECTED FOR INCREASED SHANK WIDTH AND ACOMMERCIAL SIRE LINE ON PERFORMANCE AND WALKING ABILITY OF TURKEYS

The present study was initiated to determine whether walking ability ( WA) could be markedly improved without seriously compromising growth r ate and body conformation by crossing a relatively unimproved commerci al sire line (UC) with a Line (FL) selected for increased shank width and backcrossing F-1 females to UC line males. Body weights at 8, 16, and 20 wk of age were generally similar for both Lines at the time of the initial cross. The UC Line had inferior WA, shorter and narrower s hanks, and wider breasts compared with the FL line. The F-1 birds exhi bited overdominance for BW at all ages. Heterosis in BW ranged from 3. 2 to 7.8%. At 16 wk of age, the WA scores decreased (indicating improv ed WA) in the F-1 relative to the average of the parental lines. Heter osis of WA scores was -10.5% (P greater than or equal to 0.05) for mal es and -23.5% (P less than or equal to 0.05) for females. Heterosis wa s observed in the F-1 for shank length but not for other shank measure ments (width and depth). No heterosis was observed for breast width. M ortality from 8 through 20 wk of age was reduced in the F-1 relative t o the parental lines. The backcross of the F-1 females to UC males sti ll exhibited heterosis for male BW at 16 and 20 wk of age and for WA s cores, although the magnitude was reduced 50% or more. Mortality from 8 to 20 wk of age decreased in the backcross compared with the parenta l lines. The results suggest that a line exhibiting improved leg struc ture and WA, and poor conformation, such as FL, can be used to greatly improve the WA of a cross involving a sire line with poor WA but exce llent conformation. A portion of the gains in BW and breast width obta ined in the F-1 was retained in a backcross to the sire line, making s uch a crossing scheme commercially feasible.