Research Note: Three-dimensional microstructural basis for chicken eggshell translucency

Eggshell translucency, an externally observable feature, can influence consumer purchase intentions. The eggshell quality often deteriorates in aging laying hens, leading to increased eggshell translucency. Eggs exchange water vapor through the pores. It is commonly believed that the moisture remaining in the mastoid space contributes to translucent egg formation. However, the precise mechanisms underlying eggshell translucency require further structural investigations. This study aimed to explore the 3-dimensional microstructure of eggshells using micro-computed tomography (micro-CT) to provide insights into the microstructural basis of eggshell translucency. The results revealed that the ratio of pore volume to mastoid space volume was significantly higher in the high-translucency (T(H)) group than that in the low-translucency (T(L)) group (P < 0.01); however, the ratio of mastoid space to eggshell volume showed no significant difference. Additionally, measurements of the individual pore morphological features showed that the roundness of the pores in the T(H) group was significantly higher than that in the T(L) group, whereas the flatness of the pores in the T(H) group was significantly lower (P = 0.01). Eggshell porosity directly reflects the water vapor exchange capacity of eggshells, with the T(L) group exhibiting significantly higher eggshell porosity compared to the T(H) group (P = 0.02). In conclusion, based on observations of the 3-dimensional microstructure of eggshells, this study elucidated how the volume and morphological characteristics of pores influence the water vapor exchange capacity of eggshells, resulting in eggshell translucency.