Estimation of dominance variance and its effects on the evaluation of the genetic parameters for carcass quality traits

In order to determine the interference of dominant effects on the estimation of genetic parameters, two models including additive and additive-dominance were used for estimation of genetic parameters of carcass traits in 631 hybrid beef bulls. Data analysis was conducted using Plink (V. 1.9) and GVCBLUP (V. 3.9) softwares. Results of this study showed that most carcass quality traits have high heritability,but two traits namely hot carcass weight and ultrasound ribeye area had low heritability (0.15 and 0.11). Dominance variances have high contribution to the total variation of hot carcass weight, ultrasound ribeye area, ultrasound backfat thickness and ribeye area (0.13, 0.44, 0.89 and 0.33 respectively). However, dominant effect for other traits (lean meat yield, marbling score, backfat thickness, ultrasound ribeye area and grade of carcass) was not observed or was in very low amount. When dominance variance is low, its effect on GBLUP estimates is negligible. The estimates of heritability did not change significantly by the adding dominance effect into the model. The most important genomic regions that affect the carcass quality traits were belong to LAP3, THBS4 and PCDH9 genes. It is suggested that for the better understanding of the genetic structure of traits and better breeding plan, the dominance effects should be added into the model for geneticparameter estimation.