Determining mechanical properties and type of fracture of osseous tissues from spent hens

Abstract

This study was undertaken to evaluate shear, bending, and torsion test procedures on the radius, ulna, humerus, femur, tibia, and tarsometatarsus of 72 week old caged layers. Shear and bending properties were determined to evaluate the effects of juvenile protein feeding sequence, body size, and cage profile on the strength of these bones. Body size affected (P < 0.05) the ultimate shear forces of the femur, tibia, and tarsometatarsus. The ultimate bending force and shear modulus of the tibia were also influenced by body weight (P < 0. 05). Juvenile protein sequence and body weight affected the torque and torsional shear stress of the tibia. No differences were noted in shear and bending strength when bone geometry as well as force was considered. The frequency pattern of the bending fractures occurring in the radius, ulna, femur, and tibia were influenced by juvenile protein feeding sequence (P < 0.05). The bones from the control birds failed in bending due predominantly to a weakness of tensile stresses. The reversal in protein caused the bones to fail due to a combination of tensile and shear stresses. The torsion test of the tibia and radius showed. the failure pattern to follow a 45 degree helix around the diaphysis of the bone which is indicative of tensile failures. The four point bending test was not desireable for determining the modulus of elasticity of poultry bones with a length to diameter ratio less than 10. No correlations were found between shear and bending properties of any of the bones. Similarly, the shear, bending, and torsion properties of the tibia were not related.