Direct additive, environmental, and phenotypic variances and covariances and coefficients of heritability for underline score in Beefmaster cattle

The objective of this study was to determine estimates of heritability for underline score (UDLS) and genetic, environmental, and phenotypic correlations (rg, re, rp, respectively) of UDLS with conformation score (CONS), birth weight (BRWT), weaning weight (WNWT), and yearling weight (YRWT) in Beefmaster cattle born between 1976 and 2008. Records provided by Beefmaster Breeders United (n = 49,533) for UDLS and CONS and BRWT (n = 10,698), WNWT (n = 22,503), and YRWT (n = 8,316) were studied. Data were analyzed using single- or 2-trait animal models with DFREML (Boldman et al., 1993) and DMU (Madsen and Jensen, 2013). The mixed model included fixed contemporary group effects constructed using herd, birth year, and sex information. Age of dam and animal age at inspection were included as covariates. Coefficients of heritability were 0.44 ± 0.01, 0.43 ± 0.01, 0.75 ± 0.04, 0.60 ± 0.02, and 0.85 ± 0.06 for UDLS, CONS, BRWT, WNWT, and YRWT, respectively, from the single-trait analyses. From the 2-trait analyses, coefficients of heritability for UDLS with CONS, BRWT, WNWT, and YRWT were 0.43 ± 0.01, 0.35 ± 0.05, 0.39 ± 0.03, and 0.40 ± 0.06, respectively. Coefficient of rg for UDLS with CONS was −0.16 ± 0.02, UDLS with BRWT was 0.02 ± 0.07, ULDS with WNWT was 0.05 ± 0.04, and UDLS with YRWT was 0.13 ± 0.08 from the 2-trait analyses. Mean estimated breeding value of UDLS was 0.00 ± 0.40. These results suggest that artificial selection for UDLS would be effective in beef breeding programs.