Relationships among dual-energy X-ray absorptiometry, bioelectrical impedance and ultrasound measurements of body composition of swine

In three separate studies (156 pigs total), dual-energy X-ray absorptiometry (DXA), bioelectrical impedance (BIA) and ultrasound were compared as methods for measuring live body composition of pigs at 60 and 100-110 kg BWt. DXA measured total body fat and lean content, BIA measurements of resistance (Rs) and reactance (Xc) were used to calculate total body lean mass and ultrasound measurements of backfat (BF) depth and longissimus muscle area (LMA) were used to calculate total carcass lean mass. Following the 100-110 kg measurements, the pigs were slaughtered and the half-carcass analyzed chemically for fat and water content. At 110 kg both DXA and ultrasound measurements were significantly correlated with the percentages of carcass fat and water, although correlations were higher for DXA. The correlations between DXA and BF measurements were higher at 110 kg than at 60 kg, whereas they were lower for DXA and LMA. For pigs measured at 100 kg there were high correlations between the DXA values and the BIA estimates for both percentage of fat-free lean mass (FFM %) and FFM kg. Furthermore, the correlations between the BIA estimates of FFM and carcass fat and water content were similar to those for DXA and the same carcass values. This study also provided a side-by-side comparison of the BIA and ultrasound lean measurements relative to DXA and carcass composition. The BIA lean measurement correlated more highly with both DXA and carcass composition than did the ultrasound lean measurement.