The accurate estimation of additive and dominant genetic effects is fundamental to improving the accuracy of selective breeding and accelerating genetic gains. This study harvested 29523 individuals from 343 full-sib families (244 half-sib families) and examined the G7, G8, and G9 generations. The variance components of harvest body weight for four datasets (G7, G8, G9, and G8+G9) were estimated using average information restricted maximum likelihood. Two single-trait animal models were used for the analysis:(1) an additive genetic model comprising additive genetic effects plus common environmental effects (A+C), and (2) an additive-dominant model that includes dominant genetic effects (D) (A+D+C). For the A+C model, heritability estimates of harvest body weight for the four datasets were all low ( ≤ 0.15), ranging from 0.046 to 0.082. For the A+D+C model, heritability ranged 0.063-0.096, and the ratio of dominant genetic variance to phenotypic variance spanned 0.027 to 0.571. Harvest-body-weight heritability decreased in three datasets (G7, G9, and G8+G9), while increasing in G8. Low heritability estimates indicate that wild or improved populations with strong production performance must be introduced and integrated with the nucleus breeding population. Additionally, large between-dataset differences in the ratio of dominant genetic variance to phenotypic variance suggest that the accuracy of dominance variance estimates should be improved with new algorithms including more generations.