Laboratory Measurements of Eggshell Strength

Specific gravity, non-destructive deformation, puncture force, and compression fracture force measurements were obtained from 860 eggs collected from three flocks of Single Comb White Leghorn hens. Compression fracture and puncture force measurements indicated that tensile and shear fracture resistances of the shell material were related on a within egg basis and that the correlation between fracture shear stress and shell thickness was low. Linear relationships were found between specific gravity and both puncture force and fracture shear stress while there was an apparent curvilinear relationship between these force measurements and non-destructive deformation. Stepwise regression analyses indicated that non-destructive deformation accounted for the most variation in predicting compression fracture force (54%). It was found possible to measure puncture and compression fracture force, in that order, on the same egg. Deformation measurements obtained using horizontally applied forces closely matched those obtained with the forces applied to the egg vertically.