Variance components, degree of variance explained by pen effects, and genetic trends were also reported based on the following univariate linear mixed model y = Xb + Zaa + Zpp + e, in which y = vector of phenotypes for a given trait, b = vector of fixed effect [section-year-season effect (section is a close barn containing several pens at specific time)], X = incidence matrix for fixed effect, a = vector of random animal effects, p = vector of random pen effects, Za = incidence matrix for random animal effects, Zp = incidence matrix for random pen effects, and e = random residual effects.