Genetic influences on beef longissimus palatability in charolais- and limousin-sired steers and heifers.

Random matings of 10 Charolais sires and eight Limousin sires to crossbred cows produced 392 steers and heifers that were used to evaluate genetic influences on beef palatability. Longissimus lumborum steaks were measured for shear force at 1, 4, 7, 14, 21, and 35 d postmortem and for taste panel attributes at 14 d postmortem. Longer postmortem aging periods resulted in lower (P < .05) shear force values for progeny from all 18 sires. Shear force variation among sires did not diminish during postmortem aging; however, shear force variation among progeny within a sire decreased during postmortem aging. Median within-breed heritability estimates from Method-R were .33 for shear force, .49 for 24-h calpastatin activity, and .18 for marbling score. All taste panel attribute heritability estimates were very low. Solid evidence existed for a very high within-breed genetic correlation between calpastatin activity and shear force. However, the across-breed genetic correlation between marbling and shear force seemed to be higher than the correlation between calpastatin activity and shear force. Very few antagonistic genetic relationships existed between production/carcass traits and palatability traits.