BIOELECTRICAL-IMPEDANCE CAN PREDICT SKELETAL-MUSCLE AND FAT-FREE SKELETAL-MUSCLE OF BEEF-COWS AND THEIR CARCASSES

Multiple linear regression equations predicting total skeletal muscle (TM) and total skeletal fat-free muscle (TFFM) weight were developed from data of 33 beef cows. Animals varied in weight (385 to 749 kg), age (3 to 10 yr), and fatness (.13 to 2.54 cm). A four-terminal impedance meter/ plethysmograph measured resistance and reactance on the live animals, exsanguinated (bled) animals, and on the subsequent hot and cold carcasses. Stainless steel, sterile needles (20-gauge) were used as electrodes. They were inserted to depths of 12.7 mm for measurements made before and after exsanguination and to 25.4 mm for carcass measurements. Cold carcass resistance and reactance were measured a second time using 13-gauge needles inserted to depth of 76.2 mm. Distance between detector electrodes was measured. Carcass sides were physically separated into muscle, fat, and bone. Chemical composition (moisture, protein, and fat) was determined on the muscle portion. Equations predicting TM weight from live, bled, hot carcass, and cold carcass data had adjusted R(2) values of .90, .96, .94, and .92, respectively. Analogous adjusted R(2) values for TFFM weight were .87, .93, .90, and .87. Resistance was a predictor variable in all equations. The use of larger needles resulted in higher adjusted R(2) values and inclusion of reactance as a predictor variable. Mallows Cp values were close to the ideal value of the number of independent variables in the prediction equations plus one(1). Results indicate that bioelectrical impedance technology is a rapid, nondestructive, and accurate method for determining TM and TFFM weight of beef cows and carcasses. This demonstrates that bioelectrical impedance has the potential to be used as a value-based marketing tool. Because these measurements can be easily obtained on live animals with no detrimental effects, it has the potential to be used for the genetic selection of superior animals.