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Title: BODY COMPOSITION ASSESSMENT AND MODELS: BODY COMPOSITION ANALYSIS OF PIGS FROM 5 TO 97 KG BY DUAL ENERGY X-RAY ABSORPTIOMETRY

Author
item Mitchell, Alva
item SCHOLZ, ARMIN - UNIVERSITY BERLIN
item Conway, Joan

Submitted to: Applied Radiation And Isotopes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: The rigorous validation of the use of dual energy x-ray absorptiometry (DXA) for measuring body composition requires a large number of observations covering a wide range of size and composition and the ability to compare the DXA results to accurate direct or chemical analysis. Although the body conformation of the pig differs from that of the human, this should be independent of body composition measurement by DXA. The average for the DXA measurement of percent fat in the body of pigs was 17% less than that determined by chemical analysis, however, this difference could be corrected by the application of a prediction equation. The use of the DXA measurement of lean body mass to predict protein or water content resulted in small but significant overestimation, indicating the need for further validation.

Technical Abstract: A total of 231 pigs were anesthetized and then scanned by DXA using a Lunar DPXL instrument. The weight of the pigs ranged from 5 to 97 kg (avg. = 37.7 kg). Of the total, 98 pigs were scanned using the pediatric mode and 133 pigs were scanned using the adult mode. After scanning, the pigs were euthanized, the entire body homogenized by grinding, and analyzed chemically for fat, water, protein and total body mineral content. The mean value for the DXA total tissue mass (37.1 kg) was not significantly (P>.05, n = 231) different from the mean body weight. The mean DXA value for percent fat was 14.6 and was significantly less (P<.05) than the mean value (17.6%) measured by CHEM analysis. The greatest discrepancy occurred in pigs with less than 15% body fat. From a prediction equation using the DXA R value [% fat = 493 -349(DXA R value)], the DXA estimated percent fat was 18.0%, compared to 17.6% by CHEM analysis (P>.05). Using a prediction equation [g protein = -1.062 + 0.22(g DXA lean)], the DXA estimate for body protein content was 17.8%, compared to 17.1% (P<.05, n = 131) by CHEM analysis. The DXA estimate for body water content [g water = 508 + 0.74(g DXA lean)] was 63.8%, compared to 62.6% (P<.05, n = 231) by CHEM analysis. The bone mineral content of 83 of the pigs measured by DXA was 2.40%, compared to 2.54% (P<.05, n = 83) estimated from CHEM analysis of total body ash [g bone mineral = g total body ash - 0.0085(g DXA lean)].