The morphological, material-level, and ash properties of turkey femurs from 3 different genetic strains during production

Femoral fractures are observed in selectivebred commercial turkeys; however, the etiology of such fractures is unknown. The current study investigated the whole bone morphological, material-level mechanical, and bone ash properties to determine the effect of selective breeding on bone strength. Femora from 3 divergent strains of turkeys, a commercial line, a different selectively bred heavy line (F-line), and a lighter age or weight matched random-bred line (RBC2/R-EQ, respectively), were compared. Bone geometric properties were measured with micro-CT and bone mechanical properties were measured using 3-point bending tests. Whole bone ash quantities were also recorded. Statistics were run using a general linear model multivariate ANOVA (GLM ANOVA). Results showed that at similar ages, the faster growing birds (commercial and F-line) had femurs twice the size of the RBC2 line as measured by cross-sectional area as early as 8 wk into the study. The femurs of the commercial and Flines also exhibited as much as 20% greater mechanical strength than femurs from the RBC2 line at 16 and 20 wk of age as measured by properties such as elastic modulus and ultimate tensile strength. However, at similar BW, the slower growing R-EQ line had higher mechanical properties than the other lines, with the elastic modulus being 40% greater and the ultimate tensile strength being 37% greater at weights equivalent to those of the commercial and F-lines at 12 wk of age. Moreover, it was observed that the morphological properties (i.e., cross-sectional area, moments of inertia) are largely governed by BW, as there is little difference in the amount gained per week of age across the different lines. Conversely, the mechanical properties, as well as the related ash content, appear to be governed at least in part by time. Therefore, whereas modulation of bone geometry is the key responder for changes in BW, sufficient time for matrix mineralization or maturation or both to occur is also essential for mechanical competence of bone.