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, and round were developed from data of 33 beef cows. Primal cuts were obtained in accordance with NAMP specifications. A four-terminal impedance meter/ plethysmograph measured resistance and reactance on each cut using 20- and 13-gauge needles as electrodes. Weight, internal temperature, and distance between detector electrodes were recorded. Each cut was physically separated into muscle, fat, and bone. Chemical composition (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 the percentage of fat from the proximate analysis. The predictor variables for all combinations of cuts and electrode sizes were weight, distance between detector electrodes, temperature, and resistance, except for the round for which reactance was a fifth predictor. The P value for the resistance coefficient was < .001 for all 16 prediction equations. Adjusted R2 values of the prediction equations ranged from an average 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 variables in the prediction equations plus one (1). Prediction equations for the different size electrodes were similar. An equation was also developed to predict percentage of intramuscular fat ("as is") of the longissimus muscle (adjusted R2 = .83). Results showed that bioelectrical impedance is a rapid, nondestructive, and accurate method for aiding the determination of TM and TFFM weight of beef cow primal cuts and can be used as a value-based marketing tool. Results further suggested that bioelectrical impedance may be able to objectively measure intramuscular fat content.