Genetic properties of egg quality traits and their correlations with performance traits in Japanese quail

1. Performance traits were measured on 1908 Japanese quail and egg quality traits assessed on 1800 eggs at 10 wk of age. 2. Genetic and phenotypic correlations were estimated using a bivariate animal model with restricted maximum likelihood using ASREML software. 3. Body weight at different ages showed positive genetic correlations with egg weight and most of the internal egg quality traits, whereas their genetic correlations with eggshell thickness, eggshell strength and eggshell percentage were negative. 4. Genetic correlations of age at sexual maturity and egg number with most of external and internal traits were negative. 5. It was concluded that selection for higher body weight will result in heavier and better quality eggs. Because of the negative genetic correlation between BW and egg shell quality, a selection index including BW and eggshell strength would be the best breeding strategy for genetic improvement of egg quality in Japanese quail.