Incremental changes in total and regional body composition of growing pigs measured by dual-energy x-ray absorptiometry

The pig was used as a model for the application of dual-energy x-ray absorptiometry (DXA) for measuring changes in total and regional body composition that accompany body growth. Ten pigs were scanned at the beginning of the study (26.3 +/- 8.2 kg) and at 14 day intervals until reaching a final weight of 88.6 +/- 2.3 kg. Final body composition was validated by chemical analysis of the carcass. DXA fat and lean tissue measurements were corrected by using values based on previous calibration studies. From individual growth curves, rates of fat (295 +/- 50 g/d), lean (531 +/- 50 g/d) and bone mineral (16.7 +/- 1.4 g/d) deposition rates were estimated. Furthermore, using regional analysis these tissue deposition rates partitioned into front legs, back legs and body trunk. The final DXA measurements of 87.5 kg for total tissue mass, 27.9% for percent body fat and 24.4 kg for total fat mass were not significantly different (P > .05) from direct or chemical measurements. The DXA measurement of bone mineral content 1912 g (2.18%) was similar to the estimate based on total body ash, 1980 g (2.23%). Also, from the final DXA values for lean tissue mass, it was predicted that the body contained 13.5 kg or 15.4% protein and 45.74 kg or 52.3% water. These results indicate that DXA could be an appropriate method for studies involving sequential measurements of body composition during growth.