GENETIC AND PHENOTYPIC (CO)VARIANCES FOR GROWTH AND CARCASS TRAITS OFPUREBRED AND COMPOSITE POPULATIONS OF BEEF-CATTLE

Least squares means, genetic (sigma(g)), and phenotypic (sigma(p)) sta ndard deviations, and phenotypic coefficients of variation (CV) were e stimated on an age-constant basis for growth, carcass, and meat traits of castrate males from 12 breed groups combined, for 9 purebreds comb ined, and for the F-3 generation of three composite populations combin ed to which the nine purebreds contributed. Also, heritabilities (h(2) ) and genetic (r(g)) and phenotypic (r(p)) correlations were estimated among growth, carcass, and meat traits for all breed groups combined involving 1,594 individuals that were the progeny of 306 sires (214 pu rebred and 92 composites). Coefficients of variation and sigma(g) gene rally were similar for composites and contributing purebreds for growt h and size-related traits. For traits relating to carcass tenderness, juiciness, and flavor were below .30. composition and meat quality, me ans, sigma(p), or CV for composites and contributing purebreds general ly were similar. Generally, estimates of sigma(g) and h(2) were simila r among all breed groups combined, contributing purebreds combined, an d composites combined. Generally, r(g) were high among all measures of carcass fat, indicating major difficulty in achieving a high percenta ge of retail product simultaneously with a high fat content of the lon gissimus muscle that is required for carcass quality grade. Generally, r(p) were of smaller magnitude than r(g). All r(p) of marbling score or percentage of ether-extracted fat in the longissimus muscle with al l end-use properties relating to palatability including shear force, a nd sensory evaluation of tenderness, juiciness, and flavor were below .30.