Heritability of Exterior Egg Quality Traits in Japanese Quail

Abstract

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), specific gravity (ESG), width (WE) and height (HE) of egg, shape index (ESI), shell thickness (ST), shell weight (SW), shell ratio (SR), egg surface area (ESA), and shell weight per unit surface area (SWUS) were measured. The restricted maximum likelihood procedure was 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 had high and negative genetic correlations with EW, they were -0.93 and -0.88, respectively. The genetic correlations between ESG and each of ST, SW, and SWUS were high and ranged from 0.56 to 0.82, whereas genetic correlations between ESG and the traits related with egg size were low and insignificant, ranging from -0.01 and 0.08. Therefore, selection based on ESG would be feasible to improve the ST and consequently high shell stiffness without antagonistic effect on egg size. Positive correlations between ESI and EW were higher in magnitude than the negative correlations between ESI and HE. This indicates that egg size is limited by the WE rather than HE. Shell ratio and SWUS were negatively correlated with EW, WE and HE, indicating larger eggs had proportionately less SW and consequently low SWUS. Hence, selection for increased EW will result in decreased shell quality

Keywords

• genetic parameters, shell quality, specific gravity