Genetic relationships between sex -specific traits in beef cattle: Mature body size of cows and carcass traits of their steer relatives

Data from the first four cycles of the Germplasm Evaluation Program at the US Meat Animal Research Center were used to investigate the genetic relationships between mature size of females (weight, height and body condition score) and carcass traits measured on their steer paternal half-sibs. Co-variance components of and among mature weight (MW), body condition score (BCS), MW adjusted for BCS (AMW), and height (HT) measurements from 4 to 8-yr old cows and carcass traits of steers were estimated using REML procedures. Estimates of heritability for hot carcass weight, retail product percentage, fat percent, bone percent, rib eye area, adjusted fat thickness, estimated kidney, pelvic and heart percentage, marbling score, Warner-Bratzler shear force, and taste panel tenderness measured on steers were moderate to high (0.26 to 0.65). Estimates of heritability for taste panel flavor and taste panel juiciness were low and negligible (0.05 and 0.01, respectively). Overall estimates of heritability were moderate to high for MW, AMW and HT (0.52, 0.57, 0.71; respectively) and relatively low for BCS (0.16). Pair-wise analyses for each component trait of female mature size with each carcass trait used bivariate animal models. Standard errors for genetic correlations were obtained by reparameterizing to an equivalent single trait model. Estimates of genetic correlations between cow mature size and carcass composition or meat quality traits were relatively low. Whether MW should be adjusted for BCS is arguable. Selection for most carcass and meat traits could be effective and would lead to only minor, if any, changes in mature size of cows. Selection for cow mature size could be effective and would not be expected to result in antagonistic correlated responses in carcass and meat composition traits. An equivalent single-trait model was developed, which could be useful for obtaining standard errors of estimates of genetic correlations between two traits for some situations