No G×E on egg qualities and body weight between cage and floor systems, implications for breeding programmes in laying hens

International audienceThe main objective of this study was to quantify genotype-by-environment interactions for egg quality traits and body weight in laying hens between cage and cage -free systems. Records of 18,524 eggs for quality traits and 10,266 hens for body weight from a pedigreed Rhode Island Red line were used. Hens were hatched across 5 batches from 2018 to 2020, siblings are housed in two systems: a cage and a floor system. Random regressions were modelled to estimate variance components. Heritability estimates were moderate to high in both systems(0.29-0.77). Genetic correlations between the cage and the floor system were high (≥0.79), and genetic correlations between the intercept and the slope of the reaction norm ranged from -0.69 to 0.27. The results indicate that there is no need to maintain a dedicated breeding programme per system, if the breeding goals are identical, which is unlikely