Relationships Between Kidney, Pelvic, and Heart (KPH) Fat and Beef Carcass Yield

The contribution of kidney, pelvic, and heart (KPH) fat to predicting carcass yield in the official USDA Yield Grade equation has been questioned in the modern U.S. slaughter cattle population and has not been extensively studied. Many U.S. beef processors remove KPH fat at harvest to facilitate faster chilling and easier fabrication. The objective of this study was to understand the modern-day relationship of KPH fat to subprimal yield (SY). Fabrication data from carcasses (N = 816) evaluated across multiple studies in the last 15 y were summarized. SY, subprimal cutout value (SCO), and KPH percentage were adjusted to account for study effects. Values for SY, SCO, and KPH percentage were computed on a conventional (hot side weight [HSW] including KPH) and alternate (HSW without KPH) basis, and variance among these measures was tested. Relationships among HSW and carcass components, carcass components themselves, and conventional and alternate calculations of SY and KPH percentages were evaluated using linear and quadratic models. Variance in alternate KPH percentage was greater (P = 0.01) than conventional KPH, suggesting that variance in KPH was independent from variance associated with HSW. Among carcass components, KPH weight was least related (R2 linear = 0.167, and R2 quadratic = 0.201) to HSW. Subprimal (SUB) and fat, bone, and trimmings (FBT) weight were each more directly related (R2 = 0.899 to 0.953) to HSW. Weight of KPH was poorly related to weight of SUB (R2 = 0.074) and FBT (R2 = 0.127), although quadratic relationships of these same metrics were slightly stronger. Therefore, to increase accuracy, future models predicting carcass yield should incorporate an accurate measure of KPH or exclude KPH altogether from the denominator of the yield calculation.