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Evaluation of the Prediction of Alternative Measures of Pork Carcass Composition by Three Optical Probes

Department of Animal Sciences, Purdue University, West Lafayette, IN 47907-2054

aschinck{at}purdue.edu

Abstract

The accuracy of three optical probes (HGP4, Hennessey Grading Probe, PG-100 and PG-200) to predict the carcass percentage of five alternative measures of carcass composition: fat tissue-free lean (FFLM), lipid-free soft tissue (LFSTIS), lipid-free lean (LFL), total fat tissue (TOFAT) and soft tissue lipid (STLIP) was evaluated on 203 barrows and gilts of seven genetic populations. The optical probes backfat depths were more greatly correlated (P < 0.001, 0.963 to 0.983) than the LM depths (r = 0.695 to 0.734). The optical probe backfat depths were related to lean percentage (r = -0.82 to -0.88), TOFAT% (r = 0.84 to 0.88) and STLIP% (r = 0.86 to 0.87). Optical probe LM depths were weakly related (P < 0.05; r = 0.23 to 0.34) to measures of carcass lean percentage and TOFAT% (r = -0.16 to -0.26). Fat-free lean percentage was predicted with residual standard deviations (RSD) of 3.7% for equations including last rib midline backfat thickness, 2.4 to 2.7% for equations including optical probe backfat and LM depth, and 2.3% for ribbed carcass measurements. The RSD’s for the optical probe equations ranged from 2.1 to 2.4% for LFSTIS% and 2.0 to 2.3% for LFLEAN%. The RSD’s for the optical probe equations ranged from 2.9 to 3.3% for TOFAT% and 2.5 to 2.8% for STISLIP%. Quadratic and cross-product variables of optical probe fat depth, LM depth and carcass weight were significant (P < 0.05) and reduced the RSD’s of the equations. Optical probe backfat and LM measurements can be used to predict alternative measures of carcass composition. The predicted relationships in FFL% to backfat depth were nearly identical for each optical probe.

Key Words: backfat • carcass composition • measurement error • optical probe • pigs • prediction