Evaluation of electronic methods for estimation of pork carcass composition

This research covers a systematic evaluation of several hog body composition evaluation techniques on 553 hogs that were slaughtered between the summer of 1985 and the summer of 1990. The best two variable equation in predicting carcass lean weight used warm carcass weight and 10th rib fat depth. The 10th rib fat depth taken laterally to the dorsal midline and over the loin muscle area appeared to be the single most important factor in predicting carcass lean percent. The best three variable equation for live ultrasound measurement, in predicting carcass dissected lean weight, used live hog weight, last rib fat depth and loin muscle area. The best three variable equation for carcass dissected lean percent used loin muscle area and fat depth measurements at the 10th rib and a first rib backfat thickness. All live ultrasound equations generated tended to underestimate actual lean weight. A three variable equation with carcass ultrasound measured muscle area and fat depth at the 10th rib and warm carcass weight gave R$\sp2$ =.78 and RSD = 2.10 kg in predicting carcass dissected lean weight, and an R$\sp2$ =.72 and RSD = 2.31% in predicting carcass lean percent. A two variable equation measured by the Destron optical fat-lean probe with last rib fat depth measured by the probe and warm carcass weight estimated carcass dissected lean weight with R$\sp2$ =.75 and RSD = 2.43 kg. Inclusion of a second fat depth measurement, increased the R$\sp2$ to.77 and reduced the RSD to 2.34 kg. Fat-o-Meater measured fat depths were highly correlated with chilled carcass direct measured fat depth. The 11th rib fat-depth measured by the Fat-o-Meater was the single most important factor in estimating carcass dissected lean percent. Carcass dissected lean weight was accurately estimated by EMSCAN HA-2 electromagnetic scanning of eviscerated warm carcass sides. Electromagnetic scanning of warm carcass sides also accurately predicted dissected lean weight in the ham and shoulder. However, in predicting dissected lean weight in the loin, accuracy dropped. TOBEC readings combined with 10th rib fat depth, warm carcass weight, primal cut weight, warm carcass length, or warm carcass temperature accurately estimates fat-free lean mass in carcasses and/or primal cuts. More than one carcass composition evaluation system can be used to improve prediction accuracy. (Abstract shortened with permission of author.