Relationships between intramuscular fat and dissected fat in the beef carcass

Abstract

Quantitative relationships between total dissected fat and weight of intramuscular fat in nine 'standard muscle groups' and total side muscle were investigated in 18 steer carcasses varying in fatness from 9.1 to 38.9% of chilled side weight. A simple correlation matrix showed that both weight and percentage of total dissected fat were more highly correlated with the proportion by weight of intramuscular fat in total side muscle than in any of the 'standard muscle groups'. Predictions of total dissected fat weight from regressions of the intramuscular fat percentages of 'standard muscle groups' and total side muscle were not as accurate as a relatively simple equation employing fat thickness at the 10th rib together with chilled carcass weight. For all six muscle groups used in regression equations, the percentage of total dissected fat in the carcass was more accurately predicted than total dissected fat weight. Standard muscle group 7 was the most accurate of the muscle groups in predicting total dissected fat weight, and it contained the fewest muscles (five), but they were large, expansive muscles which required extensive trimming. Standard muscle groups 3 and 7 were equally accurate in predicting total dissected fat percentage, but the former was associated with even greater dissection and trimming problems than standard muscle group 7. It is concluded that the use of intramuscular fat weight of muscle groups to improve predictions of carcass fatness is neither practicable nor successful.