The objective of this study was to estimate the genetic and phenotypic parameters for Japanese quail external egg quality traits.In this study, 1567 eggs were collected out of 584 Japanese quails which were caged individually. Egg weight (EW), specificgravity (ESG), width (WE) and height (HE) of egg, shape index (ESI), shell thickness (ST), shell weight (SW), shell ratio (SR), eggsurface area (ESA), and shell weight per unit surface area (SWUS) were measured. The restricted maximum likelihood procedurewas applied to estimate heritability and genetic and phenotypic correlations for the examined traits. Heritability of EW, ESG, WE,HE, ESI, ST, SW, SR, ESA, and SWUS were 0.83, 0.31, 0.68, 0.72, 0.59, 0.53, 0.08, 0.31, 0.83, and 0.19, respectively. Shell weight,WE, and HE had high positive genetic correlations with EW and they were ranged from 0.52 to 0.94. However, SR and SWUS hadhigh and negative genetic correlations with EW, they were -0.93 and -0.88, respectively. The genetic correlations between ESGand each of ST, SW, and SWUS were high and ranged from 0.56 to 0.82, whereas genetic correlations between ESG and the traitsrelated with egg size were low and insignificant, ranging from -0.01 and 0.08. Therefore, selection based on ESG would be feasibleto improve the ST and consequently high shell stiffness without antagonistic effect on egg size. Positive correlations betweenESI and EW were higher in magnitude than the negative correlations between ESI and HE. This indicates that egg size is limitedby the WE rather than HE. Shell ratio and SWUS were negatively correlated with EW, WE and HE, indicating larger eggs hadproportionately less SW and consequently low SWUS. Hence, selection for increased EW will result in decreased shell quality.
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