Shell Evaluation of White and Brown Egg Strains by Deformation, Breaking Strength, Shell Thickness and Specific Gravity: 1. Relationship to Egg Characteristics

Abstract

Phenotypic correlations were calculated between measures of egg shell strength obtained by non-destructive deformation, breaking strength, shell thickness and specific gravity of five commercial white and brown egg strains. Correlations between values obtained by all methods were highly significant for all strains. Correlations between the strength measurements and the egg characteristics of width/length ratio, egg weight and tint of the shell between the strains were also determined. The correlations between the tint of brown shells with all methods of evaluating shell quality were not significant. Although the shell thickness, specific gravity and shell deformation values of the brown egg strains were poorer than that of the white egg strains, the breaking strength of shells from brown egg strains was higher. This indicates that thinner shells are not necessarily weaker and suggests caution against drawing conclusions from only one method of assessing shell strength. Coefficients of variation were larger for shell deformation and breaking strength measurements than for shell thickness and specific gravity. Shape (width/length ratio) and egg weight showed little correlation with any methods of assessing shell strength.