The influence of genetic increases in shank width on body weight, walking ability, and reproduction of turkeys.

Body weight and breast width have been greatly increased in the modern turkey. However, the relative amounts of leg muscles and leg bones have declined. A similar decline also occurs with age. It was theorized that this is an inherent weakness that magnifies other causes of leg problems. In an attempt to increase the relative amount of leg bone, a subline (FL) was developed by mass selection for increased shank width at 16 weeks of age from a long-term growth-selected line of turkeys (F). Shank width of FL was increased greatly by selection. The realized heritability of shank width, based on the regression of accumulated selection response on accumulated selection differential, was .33 +/- .05 over five generations of selection. Body weight of males from FL increased at a rate comparable to that of F at 16 weeks of age. However, there was no comparable improvement in body weight of FL females, resulting in a significant line X sex interaction. A similar interaction was observed for body weight at 8 and 20 weeks of age in these lines. The genetic increases in shank width in FL resulted in significantly improved walking ability of males at 16 weeks of age in comparison to F, even though body weight of males from the two lines was similar. The walking ability of FL did not change relative to the control line from which F originated. Thus, large genetic increases in body weight of males can be achieved without loss in walking ability by genetic increases in shank width.(ABSTRACT TRUNCATED AT 250 WORDS)