Influences of bioapatite mineral and fibril structure on the mechanical properties of chicken bone during the laying period

Laying hens suffer from osteoporosis during their laying period, which causes bone fragility and susceptibility to fracture. This study evaluated the changes of mechanical properties of their bones during the laying period (from 18 to 77 wk) by using nano-indentation, atomic force microscope, X-Ray diffraction, and Raman spectroscopy. Results indicated that the crystallite sizes of bioapatite in femur decreased significantly from 34.45 to 29.26 nm during aging from 18 to 49 wk. Then, the value increased to 37.79 nm at 77 wk. Despite the abundance in bone (usually >50 wt.%), bioapatite mineral content showed no continuous enhancement during aging. The fibrils demonstrated more regular and organized structure during the laying period. Meanwhile the elastic moduli (E) and hardness (H) of femur increased from 10.84 to 18.39 GPa and 43.79 to 97.21 Vickers respectively during this period. The changes in mechanical properties are hence tightly related to the structure of bone (composed of both collagen and mineral), rather than directly related to the mineralogical properties of bone bioapatite. This study addressed the importance of the interaction between collagen and bioapatite mineral during the laying period of hens by microscopic, physicochemical, and mechanical analysis.