Genetic Correlation Between Yearling Body Size Traits and Carcass Traits in Hanwoo Steers

The objective of this study was to estimate genetic correlation between yearling body size measurement traits and carcass traits in Hanwoo steers on a progeny test station in South Korea. Body weights and ten frame size measurement records on 6,832 bulls and 5,916 steer progeny of the bulls born between 1996 and 2013 and raised at Hanwoo test station from six months of age were collected. Body weights (YW, kg) and frame size measurements (cm) were all adjusted linearly to 365 days of age from measures at six months of age. Steers progeny were slaughtered at 24 months of age and carcass evaluations of cold carcass weight (CWT, kg), backfat thickness (BFT, mm), eye muscle area (EMA, cm²), and marbling score (MS, 1 to 9 score; 1 as emaciated to 9 as abundant) were used for analyses. Animal models for live body measurement traits included test batch as a fixed contemporary group effect and a random animal genetic effect. Animal models for carcass traits included date of slaughter as a fixed contemporary group effect and age in days at slaughter as a covariate with a random animal genetic effect. REMLF90 program was used for variance component estimation for these genetic models. Heritability estimates of live body size measurements were in intermediate range, 0.16 to 0.32 (0.19 for YW, 0.32 for hip height). Heritability estimates of carcass traits were medial to high; 0.36 for CWT, 0.45 for EMA, 0.49 for BFT and 0.60 for MS. YW was highly correlated genetically with frame size traits (0.43 for chest width to 0.73 for hip height, body length and rump length). Genetic correlation of YW with CWT was 0.80, with EMA was 0.40, with BFT was 0.02 and with MS was 0.10. Frame size traits were highly correlated genetically with CWT (0.41 to 0.70). Genetic correlations between body size traits and EMA were moderate and positive, 0.17 to 0.40. Those between body size traits and MS were now to null, -0.04 to 0.29. Genetic correlations between body size traits and BFT were low but negative, -0.01 to -0.28. In conclusion, live body size traits are moderately heritable while carcass traits are highly heritable. The genetic correlations of live body size traits with CWT are high and positive but those with carcass component traits were low to be effectively used for indirect selection early in life.