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

We evaluated the use of dual-energy x-ray absorptiometry (DXA) for mea suring the gross body composition of small subjects in 97 pigs that ra nged from 5 to 27 kg live body weight. Scans were performed using a Lu nar DPXL densitometer in the pediatric mode (Version 3.8e). The DXA sc ans of the live pigs provided measurements of total fat, lean, and bon e mineral content. After scanning, the pigs were killed, the entire bo dy was ground, and samples were analyzed chemically (CHEM) for fat, pr otein, ash, and water content. We found that DXA significantly underes timated the percentage of fat in the body (DXA, 6.9 +/- .33% vs CHEM, 10.9 +/- .31%, P < .001). The correlation (r) between DXA and chemical measures of percentage fat was .86 and for grams of fat it was .96. L ean tissue mass measured by DXA was highly correlated with CHEM measur ements of total grams of body water (r = .99), total grams of body pro tein (r = .94) and lean body mass (r = .99). The average DXA bone mine ral content was within 2% of the amount estimated from total body ash and the correlation between the two values was .94. The relationships between DXA and CHEM measurements for percentages of body composition of pigs that weighed between 5 and 27 kg are described by the followin g regression equations: %fat(CHEM) = 5.22 + [.817 . fat(DXA)], (r = .8 6, standard error of the estimate, SEE = 1.56); %protein(CHEM) = -7.8 + [.256.%lean(DXA)], (r = .35, SEE = 2.3); %water(CHEM) = -5.2 + [.808 .%lean(DXA)], (r = .59, SEE = 3.67). These results are consistent with previously reported results and suggest that even though direct use o f DXA readings may not be sufficiently accurate, the high degree of co rrelation indicates that with proper calibration the DXA values can be used to predict body composition.