RESUMO
Dual-energy X-ray absorptiometry (DXA) provides a noninvasive way to determine lean tissue mass (LTM), fat mass (FM), bone mineral content (BMC), and bone mineral density (BMD) in humans and small mammals. Live channel catfish (n=74, 78g - 1200 g) were anesthetized and scanned in both a lateral position and a dorsa-ventral position. Six individual fish (300g - 600g) were scanned five times each to determine precision by the coefficient of variation. Precision was good for LTM (0.75-1.06%) and for BMC and BMD (2-2.6%). Precision for FM was not good (27-34%), which was due to the very low FM (0-1g) recorded by the DXA. However, using the predicted values, FM precision improved to 5-5.5%. DXA values for LTM, FM, and BMC were significantly different from chemical analysis (P< 0.001). DXA overestimated LTM and underestimated FM and BMC. However, all three compartments were strongly correlated with carcass values (P <0.0001). Using the prediction equations and the jackknife procedure, predicted values of LTM, FM, and BMC were not significantly different from the carcass values (P >0.05). DXA may also be a valuable tool for evaluating body condition longitudinally in commercial or in threatened or endangered fish species, where non-invasive procedures would be invaluable.
