SECOR, S.M.*; NAGY, T.R.: Determination of lean, fat, and ash mass of snakes using dual-energy X-ray absorptiometry (DXA)
Non-invasive measures of body composition (lean and fat mass, and bone mineral content) are crucial for studies in energetics, reproduction, and the regulation of body energy and mineral stores. Unfortunately, previous attempts to non-invasively determine body composition of snakes have proven problematic. We report here data on body composition of snakes determined using dual-energy X-ray absorptiometry (DXA). DXA is routinely used to determine lean and fat mass, and bone mineral content of humans, livestock, and rodents, but to our knowledge has not be used to determine body composition of snakes. We scanned 20 dead diamond-back watersnakes (Nerodia rhombifer) (body mass range: 265-1577 g) with a Lunar Prodigy DXA (GE Medical Systems, software version 3.60). Lean, fat and bone (measured as ash) masses were determined by chemical and gravimetric means for each snake and compared to DXA values. DXA values for lean body mass (r = 0.99), fat mass (r = 0.84), and bone mineral content (BMC) (r = 0.99) were significantly correlated to measured lean, fat, and ash masses. Regression equations incorporating DXA values were highly significant in predicting lean (r2 = 0.99), fat (r2 = 0.98), and ash (r2 = 0.97) mass. Mean residual differences between measured and predicted mass were 7.3 g (1.7%) for lean mass, 7.4 g (14.1%) for fat mass, and 1.6 g (6.1%) for ash mass. Therefore, DXA is a relatively accurate method to non-invasively determine lean and fat mass, and bone mineral content of snakes. Supported by NIH DK56336 and AR46301.
