GENETIC-PARAMETERS FOR SEX-SPECIFIC TRAITS IN BEEF-CATTLE

Data from 3,593 beef heifers and 4,079 of their steer paternal half-si bs were used to estimate genetic parameters of and among female growth and reproductive traits and male carcass traits. Estimates of heritab ility for adjusted 205-d weight, adjusted 365-d weight, age at puberty , calving rate, and calving difficulty measured on females were .16, . 38, .47, .19, and .18, respectively; estimates for calving rate and ca lving difficulty were expressed on a normal scale. Estimates of herita bility for hot carcass weight; retail product percentage; fat percenta ge; bone percentage; rib eye area; kidney, pelvic, and heart fat perce ntage; adjusted fat thickness; marbling score; Warner-Bratzler shear f orce; taste panel tenderness; taste panel juiciness; and taste panel f lavor that were measured on steers at an average age of 447 d (weaning age = 185, days on feed = 262) were .50, .66, .58, .54, .61, .48, .66 , .71, .26, .31, .00, and .04, respectively. Genetic correlations were positive for heifer weights with hot carcass weight, fat percentage, rib eye area, adjusted fat thickness, marbling score, and Warner-Bratz ler shear force, and they were negative with retail product percentage and kidney, pelvic, and heart fat percentage of steers. Age at pubert y was genetically correlated with taste panel tenderness but not with other carcass traits. Calving rate had positive genetic correlations w ith fat percentage, rib eye area, adjusted fat thickness, and taste pa nel flavor, and it had negative genetic correlations with retail produ ct percentage; bone percentage; and kidney, pelvic, and heart fat perc entage. Calving difficulty had favorable genetic correlations with hot carcass weight, retail product percentage, and measures of carcass te nderness, but it was unfavorably correlated with traits that involve c arcass fatness. These results indicate that selection for some traits expressed in one sex of beef cattle may result in undesirable response s in traits expressed in the opposite sex.