An evaluation of dual-energy X-ray absorptiometry and underwater weighing to estimate body composition by means of carcass analysis in piglets

To evaluate the use of dual-energy X-ray absorptiometry (DXA) and underwater weighing (UWW) for body-composition measurements, the carcasses of eight piglets (12-wk old, 15-22 kg in weight) were dissected into muscle, fat and bone. Thereafter, the components were homogenized and chemically analyzed for fat and bone mineral mass. Body components as measured by DXA correlated closely to the carcass analysis (r = 0.90-1.0). However, DXA still overestimated significantly the bone mineral mass, lean mass and total weight, and underestimated fat mass. The reproducibility of measurements, expressed as the CV for fat mass was 13.5%, whereas for total weight, lean mass and bone mineral mass, the CV was 0.74-1.9%. Fat mass was overestimated by UWW using the equations of Siri or Kraybill (r = 0.77), but not by the equation of Lohman et al. (r = 0.69). The difference between the estimation of fat by chemical analysis and estimations by DXA and UWW was significantly affected by the amount of water in lean mass and fat-free mass.