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 f rom data of 33 beef cows. Animals varied in weight (385 to 749 kg), ag e (3 to 10 yr), and fatness (.13 to 2.54 cm). A four-terminal impedanc e meter/ plethysmograph measured resistance and reactance on the live animals, exsanguinated (bled) animals, and on the subsequent hot and c old carcasses. Stainless steel, sterile needles (20-gauge) were used a s electrodes. They were inserted to depths of 12.7 mm for measurements made before and after exsanguination and to 25.4 mm for carcass measu rements. Cold carcass resistance and reactance were measured a second time using 13-gauge needles inserted to depth of 76.2 mm. Distance bet ween detector electrodes was measured. Carcass sides were physically s eparated into muscle, fat, and bone. Chemical composition (moisture, p rotein, and fat) was determined on the muscle portion. Equations predi cting TM weight from live, bled, hot carcass, and cold carcass data ha d adjusted R(2) values of .90, .96, .94, and .92, respectively. Analog ous adjusted R(2) values for TFFM weight were .87, .93, .90, and .87. Resistance was a predictor variable in all equations. The use of large r needles resulted in higher adjusted R(2) values and inclusion of rea ctance as a predictor variable. Mallows Cp values were close to the id eal value of the number of independent variables in the prediction equ ations plus one(1). Results indicate that bioelectrical impedance tech nology 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 u sed for the genetic selection of superior animals.