Estimation of additive and dominant variance of egg quality traits in pure-line layers
Résumé
Improved performances are partly due to heterosis effects. One of the basis of heterosis is dominance, which cannot be inherited.
However, it can be exploited to boost the total genetic merit of the animals. This has a special interest in avian selection schemes
where commercial animals are crossbred. In this study, we have estimated additive and dominance genetic variances for several
egg quality traits in pure-line layers.
Around 10,500 egg quality performances were used, collected from 1,148 female Rhode Island layers, phenotyped at 70 weeks
old and genotyped using a 600K high density SNP chip. Five egg quality traits were analysed: egg weight (EW), egg shell color
(ESC), egg shell strength (ESS), albumen height (AH) and egg shell shape (ESShape). Additive and dominance genetic variances
were estimated via EM-REML with univariate models. That included an inbreeding coefficient and an additive and a dominance
random effect. Dominance variance explained a small fraction of the phenotypic variance (between 2 to 4 % across all traits).
However, it represented a relevant fraction of the total genetic variance for some of the traits (16%, 10%, 35%, 2.4% and 15% of
the total genetic variance for EW, ESC, ESS, AH, ESShape, respectively).
Further research will estimate additive and dominance genetic correlations between the traits to maximize the total genetic gain
of these traits simultaneously. In addition, a genomic BLUP with dominance effects is envisaged for the joint analyses of purebred
and crossbred performances, to evaluate the potential to generate superior crossbred performances.
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