Genetics of meat quality and carcass traits and the impact of tenderstretching in two tropical beef genotypes

摘要

Meat quality and carcass traits were measured for 2180 feedlot finished Brahman (BRAH) and TropicalnComposite (TCOMP) steers to investigate genetic and non-genetic influences on shear force, and other meat quality traits.nGenetic and phenotypic correlations were estimated between carcass and meat quality traits, and with live animalnmeasurements collected in steers from weaning to feedlot exit, and their heifer half-sibs up to their first mating, whichnwere managed in Australia’s tropical or subtropical environments. Left sides of carcasses were tenderstretched (hung by thenaitch-bone) while right sides were conventionally hung (by the Achilles tendon). Tenderstretching reduced mean shear forcenby 1.04 kg, and phenotypic variance by 77% of that observed in conventionally hung sides. Genotype differences existed forncarcass traits, with TCOMP carcasses significantly heavier, fatter, with greater eye muscle area, and lower retail beef yieldnthan BRAH. TCOMP had lower shear force, and higher percent intramuscular fat. Meat quality and carcass traits werenmoderately heritable, with estimates for shear force and compression of 0.33 and 0.19 for BRAH and 0.32 and 0.20 fornTCOMPrespectively. In both genotypes, estimates of heritability for carcass traits (carcass weight, P8 and rib fat depths, eyenmuscle area and retail beef yield) were consistently moderate to high (0.21 to 0.56). Shear force and compression werengenetically correlated with percent intramuscular fat (rg = –0.26 and –0.57, respectively), and meat colour (rg = –0.41 andn–0.68, respectively). For TCOMP, lower shear force was genetically related to decreased carcass P8 fat depth (rg = 0.51).nForBRAHsteers and heifers measured at pasture, fatness traits and growth rates were genetically correlated with shear force,nalthough the magnitude of these relationships varied with time of measurement. Net feed intake was significantly geneticallyncorrelated with carcass rib fat depth (rg = 0.49), eye muscle area (rg = –0.42) and retail beef yield (rg = –0.61). These resultsndemonstrate that selection to improve production and carcass traits can impact meat quality traits in tropically adapted cattle,nand that genotype specific evaluations will be necessary to accommodate different genetic relationships between meatnquality, carcass and live animal traits.