Trait = weight at 6 weeks (W6W), weight growth slope (WGS), body length (BL), percentage of CD8+ cells (%CD8+), ratio between CD4+ and CD8+ cells (CD4+/CD8+). Nº QTL = number of QTL mapped, proportion of the variance explained by them (variance explained, in %) and proportion of the variance explained by the QTL with largest effect(largest QTL, in %). *Information published in Valdar et al.  and Valdar et al. .