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

Abstract

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

Production and processing studies on calpain-system gene markers for beef tenderness: Consumer assessments of eating quality1

“…The reduction was particularly noticeable for NSW Angus, where the residual variance fell from 211 to 75 units 2 . Such improvements in consistency with tenderstretching have been noted elsewhere (Sørheim et al, 2001;Wolcott et al, 2009) and are generally considered of value to consumers .…”

Importance of adaptation and genotype × environment interactions in tropical beef breeding systems

“…Significant production losses have been associated with poor temperament, particularly in intensive production systems such as feedlots (Burrow and Dillon, 1997;Petherick et al, 2002) and artificial breeding programmes (Burrow et al, 1988). Sires with poor temperament have been shown to produce progeny whose beef is less tender than progeny of sires with better temperaments Kadel et al, 2006), although Burrow et al (1999) and Wolcott et al (2009) also indicate it may be possible to overcome this negative relationship between temperament and beef tenderness through use of best practice processing techniques. Regardless, with the increasing emphasis placed by consumers on ethical production systems, it is essential to consider the animal welfare implications of handling animals with poor temperaments.…”

“…Genetic associations exist between growth traits and body composition attributes such as retail beef yield, fat depth and marbling (the review of Burrow et al, 2001 and references therein; Reverter et al, 2003a andWolcott et al, 2009) and feed efficiency (Robinson and Oddy, 2004;Barwick et al, 2009a). Genetic and phenotypic associations also exist between growth and reproductive attributes (Burrow et al, 1991;Burrow, 2001 and references therein).…”

“…Most estimates of retail beef yield percentage are also highly heritable, offering good potential for within-breed improvement, although a moderate-to-strong antagonistic relationship exists between yield and marbling, meaning that measurement of all traits will be required if unfavourable consequences of selection are to be avoided. Beef tenderness is lowly heritable in British breeds of cattle when processing factors are strictly controlled ; however, tenderness is moderately to highly heritable in B. indicus breeds (the Burrow et al, 2001 review and references therein; Johnston et al, 2003b;Wolcott et al, 2009), suggesting the trait can be improved in tropically adapted cattle by selection. However, the lack of direct measurement of beef tenderness in live animals remains a constraint for breeding programmes.…”

“…Similarly, Wolcott et al (2009) reported that genotypespecific evaluations will be necessary to accommodate different genetic relationships between meat quality, carcass and live animal traits. Brahmans and Tropical Composites were significantly different for some key meat quality and carcass traits, supporting the 'Meat Standards Australia' position that B. indicus content be included as a factor in meat quality grading (see papers in Thompson et al, 2008).…”