Effect of Uniformity of Eggshell Thickness on Eggshell Quality in Chickens

Abstract

Numerous parameters have been proposed to evaluate eggshell quality in order to reduce losses from damaged eggshells. The uniformity of eggshell thickness (UET), as a newly proposed parameter, is defined as the reciprocal of the coefficient of variation of the eggshell thickness of multiple points on the eggshell surface. In this study, we further evaluated the relationship between UET and eggshell quality of eggs from Lohmann Brown layers. Three hundred and thirty fresh eggs from 40-week-old hens were collected. Egg weight, eggshell weight, eggshell thickness, shape index, and breaking strength were measured, and UET, static stiffness, fracture toughness, and elastic modulus were calculated. The relationship between UET and other eggshell quality parameters was analyzed. Results show that UET is positively correlated with eggshell thickness, breaking strength, static stiffness, and fracture toughness (r=0.297, 0.430, 0.409, and 0.171, respectively, P<0.01). In order to analyze the effect of UET on eggshell quality, eggs were divided into three groups according to their eggshell thickness (thin, medium, and thick), and eggs within each thickness group were subdivided into three subgroups based on their UET (low, medium, and high). Relationship between UET and eggshell quality was analyzed. Result showed that eggs with higher UET in the thin group had higher breaking strength, static stiffness, fracture toughness, and elastic modulus than those with lower UET in the medium group, indicating that eggs with thinner but more uniform eggshells were stronger than those with thicker but less uniform eggshells. Our study suggested that UET has a significant influence on breaking strength, static stiffness, fracture toughness, and elastic modulus and should be included in evaluating eggshell quality.