Using current on-line carcass evaluation parameters to estimate boneless and bone-in pork carcass yield as influenced by trim level

The objective of this study was to develop prediction equations for estimat ing proportional carcass yield to a variety of external trim levels and-bon e-in and boneless pork primal cuts. Two hundred pork carcasses were selecte d from six U.S. pork processing plants and represented USDA carcass grades (25% USDA #1, 36% USDA #2, 25% USDA #3, and 14% USDA #4). Carcasses were me asured (prerigor and after a 24 h chill) for fat and muscle depth at the la st rib (LR) and between the third and fourth from last rib (TH) with a Henn essy optical grading probe (OGP). Carcasses were shipped to Texas A&M Unive rsity, where one was randomly assigned for fabrication. Selected sides were fabricated to four lean cuts (ham, loin, Boston butt, and picnic shoulder) then fabricated progressively into bone-in (BI) and boneless (BL) four lea n cuts (FLC) trimmed to .64, .32, and 0 cm of s.c. fat, and BL 0 cm trim, s eam fat removed, four lean cuts (BLS-0FLC). Total dissected carcass lean wa s used to calculate the percentage of total carcass lean (PLEAN). Lean tiss ue subsamples were collected for chemical fat-free analysis and percentage carcass fat-free lean (FFLEAN) was determined. Longissimus muscle area and fat depth also were collected at the 10th and 11th rib interface during fab rication. Regression equations were developed from linear carcass and OGP m easurements predicting FLC of each fabrication point. Loin muscle and fat d epths from the OPG obtained on warm, prerigor carcasses at the TH interface were more accurate predictors of fabrication end points than warm carcass probe depth obtained at the last rib or either of the chilled carcass probe sites (probed at TH or LR). Fat and loin muscle depth obtained via OGP exp lained 46.7,. 52.6, and 57.1% (residual mean square error [RMSE] = 3.30, 3. 19, and 3.04%) of the variation in the percentage of BI-FLC trimmed to .64, .32, and 0 cm of s.c. fat, respectively, and 49.0, 53.9, and 60.7% (RMSE = 2.91, 2.81, and 2.69%) of the variation in the percentage of BL-FLC trimme d to .64, .32, and 0 cm of s.c. fat, respectively. Fat and loin muscle dept h from warm carcass OGP probes at the TH interface accounted for 62.4 and 6 3.5% (RMSE 3.38 and 3.27%) of the variation in PLEAN and FFLEAN, respective ly. These equations provide an opportunity tp estimate pork carcass yield f or a variety of procurement end point equations using existing on-line tech niques.