Genetics of meat quality traits in two tropically adapted genotypes of beef cattle: 2. Influence of tenderstretching

Tender stretching (TS) is an alternative means of hanging beef carcasses which, when compared to sides conventionally hung by the Achilles tendon (AT), minimises the potential for muscle shortening during rigor in the high priced cuts of the rump and loin. A total of 1,939 tropically adapted steers of two genotypes (889 Brahmans (BRAH) and 1,050 Tropical Composites (TCOMP)) were used to estimate the effect of TS on the genetic parameters of meat quality traits. Measurements of meat quality traits (peak force (PF), cooking loss (CLoss) and compression (CMP)) were performed on feedlot finished steers. Heritabilities of meat quality traits were moderate in both genotypes. For BRAH heritability estimates were 0.33, 0.15 and 0.07 for PF, CMP CLoss, respectively. The heritabilities for TCOMP were 0.30, 0.27 and 0.21, respectively. Use of TS resulted in a proportional reduction in phenotypic and additive variances in comparison to conventionally hung carcases. As a result, the heritabilities of TS meat quality traits are similar to those measured on conventionally hung carcases. Despite this, the response to selection upon TS measurements will be significantly reduced, in comparison to AT, due to the reduction in additive variance. However, the reduced phenotypic variances for TS measurements suggest that commercial use of TS in the abattoir will lessen the need to select for tenderness in beef genetically.