BIOELECTRICAL-IMPEDANCE ANALYSIS FOR THE PREDICTION OF FAT-FREE MASS IN LAMBS AND LAMB CARCASSES

Ninety-eight commercial crossbred lambs, average weight 55.1 kg (+/- 4.95), were used to evaluate bioelectrical impedance analysis (BIA) as a prediction method for fat-free tissue from live lambs and lamb carcasses. Lambs were transported to the abattoir, restricted from feed for 10 h, weighed (LWt), and measured for body resistance (Rs, ohms), body reactance (Xc, ohms), and distance between detector terminals (L, cm). Following slaughter, hot carcasses were weighed (HCWt; average 31.4 +/- 2.8 kg) and impedance measurements of Rs, Xc, and L were recorded from readings on the dorsal and lateral sides of the carcasses. Temperatures (average = 39.2 degrees C) were recorded. Carcasses were chilled for 24 h. Cold carcass weights (CWt; average 31.1 +/- 2.8 kg) and temperatures (average = 1.0 degrees C) were recorded and BIA measurements were repeated. Carcasses were split down the midline and right sides were ground three times and sampled for chemical analysis of fat, moisture, ash, and protein. Fat-free mass (FFM) was calculated as [Wt - (Wt x %Fat)]. Fat-free soft tissue (FFST) was calculated as the sum of carcass chemical protein and carcass water. Regression equations predicting fat-free tissue for the live lambs (FFM(live) and FFSTlive), hot carcasses (FFM(hot) and FFSThot), and cold carcasses (FFM(cold) and FFSTcold) were developed. The independent variables LWt, Rs, and Xc accounted for 77.7% (residual mean square error [RMSE] = 1.97 kg) of the variation in FFM(live) and 78.6% (RMSE = 1.78 kg) of the variability of FFSTlive. Hot or CWt, Rs, Xc, L, and temperature detected 77.9% of the variation for FFM(hot) (RMSE = 1.04) and FFM(cold) (RMSE = 1.04) and 79.1 (RMSE = .92 kg) and 77.6% (RMSE = .95 kg) of the variation in FFSThot and FFSTcold, respectively. The results show that bioelectrical impedance has potential as a means of predicting the fat-free component of market-weight lambs and lamb carcasses.