BIOELECTRICAL-IMPEDANCE ANALYSIS FOR ESTI MATING BODY-COMPOSITION OF SOWS IN-VIVO

In 15 crossbred sows, bioelectrical impedance analysis (BIA) was perfo rmed to get regression formulas for total body water (GKW), fat (GKF), and protein (GKP). Animals were fasted 12 h, but had free access to w ater. BIA was performed by a four-terminal impedance plethysmograph, w hich supplies a current of 0.9 mA with 51.2 kHz. Adhesive silver chlor ide electrodes were used, animals were not sedated, standing on a dry floor. Live weight (LM, 145-225 kg), heart girth (BU, 112-133 cm), cro wn-rump-length (SSL, 127-160 cm), Resistance (Rs, 89-127 Ohms), Reacta nce (Xc, 18-38 Ohms) were measured. As reference method served the che mical analysis of crude water (Xw, 54.7-70.8%), fat (Xf, 4.6-23.3%), a nd protein (Xp, 16.4-20.1%) in the homogenized body to establish regre ssion formulas. By addition of Rs and/or Xc to the regression formulas accuracy was better than without Rs and/or Xc. The best results for e stimating the body composition were achieved with the following equati ons: GKW (kg) = 7.126 + 0.389 LM + 0.039 BU + 0.129 SSL(2)/Rs - 0.285 Xc (R(2) = 0.968 p < 0.001) max. error:-3.52 kg/+4.30 kg GKF (kg) = -2 7.510 + 0.296 LM + 0.197 BU - 0.183 SSL(2)/Rs + 0.613 Xc (R(2) = 0.820 p < 0.001) max. error:-5.78 kg/+8.56 kg GKP (kg) = -8.133 + 0.151 LM + 0.092 SSL - 0.011 BU2/Rs - 0.037 Xc (R(2) = 0.956 p < 0.001) max. er ror:-1.95 kg/+1.39 kg Equations for absolute contents (kg) were much b etter than for relative contents (% of total body mass). Most problems were found in estimating the body fat content from BIA regressions, b ut without Rs and/or Xc the deviation was even greater. This problem m ay possibly be diminished in progressive studies, i.e, in sows during lactation. Results stimulate for further research, espec. in type and position of electrodes, and for direct comparison with other equipment for estimating body composition in vivo.