Estimates of genetic parameters in turkeys. 1. Body weight and skeletal characteristics

Heritabilities (h2) of and genetic (rG) correlations among body weight and a number of skeletal characteristics were estimated from data on 1,088 pedigree turkeys (504 females and 584 males) of a randombred control line. All measurements were made at 16 wk of age. The h2 estimates (sire component) obtained from females (F) and males (M), respectively, were: BW .23, .60; shank width (SW) .54, .47; shank length (SL) .43, .54; drum length .66, .60; rough-cleaned weights of the thigh (nonestimable, .60), drum .09, .57, and shank .28, .69; cleaned weights of the drum .37, .71, and shank .30, .40; fat-free weights of the drum .44, .93, and shank, .45, .82; bone density measured at 40 and 60% of the length from the proximal end of the drum .68, .80 and .34, .92, respectively, and shank .28, .69 and .31, .55. Genetic correlations (rG) among the various bone weights were all above .66, with most above .85. The rG between BW and SW were .33 from M and .47 from F. These correlations suggest there is a relatively weak relationship, indicating that selection for BW alone might not cause a large enough increase in SW to support the increase brought about in BW. Shank width also had relatively low correlations with bone weight measurements, ranging from .27 to .53 from M and .17 to .56 from F. The h2 of walking ability score (WA) was .06 and the rG of WA with BW was -.73, which indicated that the low body weight families tended to have poor WA (i.e., higher scores). This may be a spurious rG, because poor walking ability scores tended to be grouped in families. Birds with poor walking ability would have difficulty eating, and would, therefore, tend to have low BW. The rG between SW:WA (-.09) and SL:WA (.03) indicated little relationship between those traits. The WA and the bone density readings had high negative rG (range -.75 to -1.47), indicating that families with poor WA ratings also had low bone density scores.