Predicting cutability of pork carcasses and hams using the Hennessy and Chong Fat Depth Indicator

Hot and cold Fat Depth Indicator (FDI) readings were taken on seventy-four pork sides to examine the relative precision of different measurement locations. Fat measurements taken over the M. longissimus opposite the fourteenth thoracic vertebra (CD = 47·5; RSD = 1·63) and the last lumbar vertebra (CD = 61·1; RSD = 1·40) were the measurement locations most closely associated with percentages of four trimmed lean cuts. Using certain combinations of carcass weight and/or hot and cold FDI readings in multiple regression equations, 71·0% (RSD = 1·35) and 63·3% (RSD = 1·55), respectively, of the variability in percentage yields of four lean cuts could be explained; this was as much as 40 percentage points more than that explained by average backfat thickness (first rib, last rib, last lumbar vertebra) taken on the split surface in the dorsal midline. When added to an unpublished equation, the addition of up to four hot or cold FDI readings made dramatic increases in the explained variation in carcass yields of four lean cuts. In each of two studies involving green, skinned hams, FDI readings explained a low percentage of the variability in percentage of boneless, defatted, deseamed lean. However, it was determined that these low relationships were primarily due to the site selections at which the hams were probed-not because of an inadequacy of the FDI to measure fatness. A third study, involving different FDI probe sites, taken on intact sides along the ham to loin-belly juncture, determined that the best of these FDI readings could account for a maximum of 66·1% of the variability (RSD = 2·75) in yield of bone-in, skinned, defatted hams; a four-variable prediction equation developed using two FDI readings, untrimmed ham weight and muscling score explained 83·9% of the variation (RSD = 2·04).