The current study investigated the influence of selection for increased egg production on external and internal egg quality traits over five generations in Japanese quail.A total of 4325 fresh eggs from 1326 females were collected each week during the egg-laying period to estimate heritability, genetic and phenotypic correlations, and correlated response of external and internal egg quality traits to selection for egg number (EN).The direct response to selection indicated an increase of 7.7 ± 0.27 eggs produced during the 90 days following production of the first egg.The correlated responses to selection indicated that selection for higher EN can be expected to increase EW and increase egg quality.Estimates of heritability ranged from 0.11 to 0.35 for external egg quality traits and from 0.08 to 0.32 for internal egg quality traits.Estimates of the genetic correlations of EN with external and internal traits were positive, ranging from 0.09 to 0.25 and from 0.02 to 0.27, respectively.These estimates indicated few if any genetic antagonisms that would adversely affect selection response.However, eggshell thickness would not be expected to change as a result of selection for EN.Thus, the external and internal quality of Japanese quail eggs could be improved by selection for high egg production.
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