BIOELECTRICAL-IMPEDANCE CAN PREDICT SKELETAL-MUSCLE AND FAT-FREE SKELETAL-MUSCLE OF BEEF COW PRIMAL CUTS

Multiple linear regression equations predicting total skeletal muscle (TM) and total skeletal fat-free muscle (TFFM) of chuck, rib, loin, an d round were developed from data of 33 beef cows. Primal cuts were obt ained in accordance with NAMP specifications. A four-terminal impedanc e meter/plethysmograph measured resistance and reactance on each cut u sing 20- and 13-gauge needles as electrodes. Weight, internal temperat ure, and distance between detector electrodes were recorded. Each cut was physically separated into muscle, fat, and bone. Chemical composit ion (moisture, protein, and fat) was obtained on the muscle portion of each cut so that TFFM could be obtained by multiplying TM x 1 minus t he percentage of fat from the proximate analysis. The predictor variab les for all combinations of cuts and electrode sizes were weight, dist ance between detector electrodes, temperature, and resistance, except for the round for which reactance was a fifth predictor. The P value f or the resistance coefficient was <.001 for all 16 prediction equation s. Adjusted R(2) values of the prediction equations ranged from an ave rage of .91 for the rib to an average of .96 for the round. Mallows Cp values were close to the ideal value of the number of independent var iables in the prediction equations plus one (1). Prediction equations for the different size electrodes were similar. An equation was also d eveloped to predict percentage of intramuscular fat (''as is'') of the longissimus muscle (adjusted R(2) = .83). Results showed that bioelec trical impedance is a rapid, nondestructive, and accurate method for a iding the determination of TM and TFFM weight of beef cow primal cuts and can be used as a value-based marketing tool. Results further sugge sted that bioelectrical impedance may be able to objectively measure i ntramuscular fat content.