BODY-COMPOSITION ANALYSIS OF PIGS BY DUAL-ENERGY X-RAY ABSORPTIOMETRY

Dual-energy x-ray absorptiometry (DXA) was evaluated as a method for m easuring body composition of pigs. Forty-eight female pigs (10.2 to 60 .5 kg) were killed and the whole bodies scanned on a DXA instrument. T he DXA measurements provided readings of total tissue mass, percentage of fat, fat tissue mass, lean body mass, and bone mineral content. By chemical analysis, the whole body fat content of the pigs ranged from 9.3 to 24.3%, giving rise to DXA R(ST) values (ratio of attenuation c oefficients) ranging from 1.386 to 1.334. The average percentage body fat measured by DXA (18.2 +/- .9%) was not significantly different (P = .76) from the results by chemical analysis (17.8 +/- 6%); however, c oncordance correlation analysis revealed unacceptable accuracy in the DXA measurement due to a negative bias for smaller percentages and a p ositive bias for larger percentages. Total body fat measured by the tw o methods was also highly correlated (r = .989), and the average for D XA (7.31 +/- .62 kg) was not significantly different (P = .89) from th e value for the chemical method (7.20 +/- .50 kg). The relationship be tween the DXA estimate of lean body mass and the amount of protein in the body by chemical analysis was described by the equation: kg protei n = .227 . kg DXA lean -1.28, with a correlation coefficient (r) of .9 68. The DXA measurements of total tissue mass and actual body weights were highly correlated (r = .999), with an acceptable concordance at t he .05 level. Scans were also analyzed for regional composition of the front and back legs. It was generally difficult to determine anatomic ally how well soft tissue described by DXA regions corresponded to tho se dissected. The DXA and chemical results for regional analysis of ba ck legs were in better agreement than those for the front legs. These results indicate that DXA may be used as a reliable method for measuri ng body composition of pigs, but needs more extensive calibration and may be more appropriate for total body rather than regional analysis.