Genetic and environmental influences on beef tenderness

Abstract

Mechanical tenderness measurements of M. longissimus (LM) and M. semitendinosus (ST) were analysed from 1392 tropically adapted (Brahman, Belmont Red and Santa Gertrudis) cattle grown out and finished in both tropical and temperate environments, and 2408 temperate breed (Angus, Hereford, Murray Grey and Shorthorn) cattle grown out and finished in a temperate environment. Groups of cattle from both environments were managed under 2 finishing systems (pasture and feedlot) to market liveweights of 400, 520 (steers and heifers) and 600 kg (steers only). Carcasses were electrically stimulated and care was taken to minimise stress before slaughter.

Estimated genetic variation (GV) of compression of unaged LM and ST muscles was 0.006 and 0.018 kg² respectively in tropically adapted and 0.004 and 0.009 kg² in temperate breeds (phenotypic means 1.7, 2.1, 1.6, 2.1 kg; heritabilities, h² = 0.16, 0.24, 0.10, 0.16). Estimated GV for LM and ST shear force was 0.24 and 0.12 kg² in tropically adapted and 0.06 and 0.02 kg² in temperate breeds (means 4.3, 4.6, 4.0 and 4.7 kg; h² = 0.38, 0.40, 0.11, 0.06). Genetic correlations among shear and compression forces of the ST and LM ranged from 0.28 to 0.95 in tropically adapted and –0.20 to 0.60 in temperate breeds. The fixed effects model (market, finish, breed, birth herd, management group and interactions) explained about half the variation in compression measurements, but only 16% and 27% of the variation of LM shear force in tropically adapted and temperate breeds.

The relatively low genetic variation and inconsistent genetic correlations in temperate breeds suggest genetic improvement in tenderness may be less important than effective pre- and post-slaughter management protocols. The higher additive genetic variances and moderate heritabilities in tropically adapted breeds suggest genetic improvement is possible but this will be most effective if combined with effective control of slaughter protocols.