Young's modulus (E) is a measure for stiffness of a material and a higher E means a higher stiffness. The respective polymorphism of the feather corneous beta-protein gene causes the replacement of glycine by cysteine. We looked for possible effects of the three FCBP genotypes on E in the 10th primaries of racing pigeons. However, we did not find a statistically significant difference of E between the genotypes, even within the sexes and/or within different locations under our test conditions. Our findings do not preclude the possibility that under other conditions (temperature, moisture) an influence of the glycine/cysteine polymorphism on E may exist. Compared to the more proximal locations of the rachis (base and middle) we observed lower values for E in the distal region (tip). The 10th primary constitutes the leading edge of the pigeon wing and this special function may require higher stiffness in the proximal parts of the shaft. We observed significantly higher values of E in females than in males, which result only from statistically significantly higher values in the middle region. The higher stiffness of female primaries may also contribute to the better results of hens compared to cocks in pigeon races.
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