title: Validation of Dual-energy X-Ray Absorptiometry to Predict Body Composition of Channel Catfish,Ictalurus punctatus.
abstract: 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.
authors.affiliation: Department of Nutrition Sciences, University of Alabama at Birmingham, Birmingham, AL 35294-3360.
authors.forename: Maria S
authors.initials: MS
authors.lastname: Johnson
authors.affiliation: Department of Biology, University of Alabama at Birmingham, Birmingham, AL 35294-1170.
authors.forename: Randall J
authors.initials: RJ
authors.lastname: Watts
authors.affiliation: Aquatic Science Department, Gadsden State Community College, P.O. Box 227, Gadsden, AL 35902-0227.
authors.forename: Hugh S
authors.initials: HS
authors.lastname: Hammer
authors.affiliation: Department of Nutrition Sciences, University of Alabama at Birmingham, Birmingham, AL 35294-3360.
authors.forename: Tim R
authors.initials: TR
authors.lastname: Nagy
authors.affiliation: Department of Biology, University of Alabama at Birmingham, Birmingham, AL 35294-1170.
authors.forename: Stephen
authors.initials: S
authors.lastname: A Watts