Simulated instrument augmentation of USDA yield grade application to beef carcasses.

Abstract

Because no instrument technology has been shown to predict beef carcass composition better than USDA yield grades, this study was conducted to determine whether an instrument could be used to augment and improve the accuracy of USDA yield grade placement. Adjusted preliminary yield grade (PYG), ribeye area (REA), estimated percentage of kidney, pelvic, and heart fat (KPH), hot carcass weight (HCW), and USDA yield grade (called and computed) were determined by five on-line USDA graders and two USDA grading supervisors for beef carcasses (n = 550) selected randomly in a commercial beef packing plant. Data were compared (2,737 comparisons) to Gold Standard yield grades and yield grade factors determined by an expert panel of carcass evaluators (unrestrained in access or time to evaluate carcasses). On-line USDA grader PYG were closely related (mean absolute error of .15 +/- .14 yield grade units; r = .91), and on-line REA and KPH were nominally related (mean absolute error of .51 +/- .35, .06 +/- .07 yield grade units and r = .48 and .66, respectively), to Gold Standard yield grade factors. On-line USDA graders determined adjusted PYG effectively, but they may require instrument assistance to evaluate carcass muscling traits and perform time-sensitive computations. To explain why instrument technology may not estimate beef carcass fatness as accurately as USDA yield grades, the absolute mean difference between Gold Standard measured PYG and adjusted PYG were compared. Only 5.6% of the sample population required no PYG adjustment, 94.4% required some adjustment, and 11.0% required over a .5 yield grade unit adjustment. Yield grades for beef carcasses, called by the USDA graders and supervisors at chain speeds, resulted in greater accuracy (absolute mean error of .24 +/- .43 yield grade units; r = .82) than when yield grades were computed for carcasses using the yield grade factors determined by on-line USDA graders and supervisors at chain speeds (absolute mean error of .52 +/- .41 yield grade units; r = .75). Gold Standard yield grade factors were sequentially substituted into the short-cut USDA yield grade equation for the yield grade factors determined at chain speeds by the USDA graders and supervisors. Results suggested that instrument augmentation would improve accuracy and precision of yield grade placement if on-line USDA graders determined PYG and an instrument determined REA and performed the necessary computations, incorporating KPH and actual HCW (P < .05).