Validation of Dual‐energy X‐ray Absorptiometry to Predict Body Composition of Channel Catfish, Ictalurus punctatus

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, 78–1200 g) were anesthetized and scanned in both a lateral position and a dorsa‐ventral position. Six individual fish (300–600 g) 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 (0–1 g) 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 noninvasive procedures would be invaluable.