genetic analysis of egg quality traits in japanese quail

the present research was conducted to analyze the genetic structure of egg quality traits in japanese quail. external and internal egg quality traits were assessed on 1706 eggs of laying japanese quail. eggs were collected for 4 days at the quaits 10 weeks of age. the investigated traits were analyzed through univariate as well as multivariate animal models employing restricted maximum likelihood method. heritability of external of eggs quality traits consisting egg weight(ew), egg length(el), egg width (ewi), egg shape index (esi), shell weight (sw), shell thickness (st) and shell yield (sy) were between 0.09 (sy) to 0.41 (ew). heritability of internal egg quality traits consisting yolk weight (yw), yolk height (yh), yolk index (yi), yolk diameter (yd), albumen weight (aw), albumen height (ah), albumen index (ai) and internal quality unit (iqu) were recorded from 0.06 (iqu) to 0.33 (yw). negative genetic correlations were found between ew with st and sy (-0.33 and -0.64, respectively). the results indicated that increasing egg weight will reduce egg shell thickness, genetically. yw showed favorable genetic correlations with yh (0.32), yd (0.96), aw (0.85) and ah (0.87). therefore, selection based on yolk weight will improve internal egg quality in japanese quail. genetic correlations of ew with most of the internal egg quality traits were positively high (from 0.77 to 0.99). based on present results, selection for higher egg weight is enough to increase internal egg quality traits. to improve both external and internal egg quality traits, it is necessary to involve have egg shell thickness together with egg weight in the selection index.