Use of the EM-SCAN (R) to determine body composition in previously frozen specimens

Changes in body composition between fat and lean tissue in mammals are the basis of many ecological and physiological studies, and certainly are impor tant in assessing energy flux in hibernators. The primary means for determi ning flux in body composition has involved large sample sizes, sacrificing animals at various times throughout an experiment. Carcasses were then chem ically analyzed for fat content. Recently, a new procedure using the EM-SCA N device has allowed determination of body composition in live animals. Thu s: an animal can be repeatedly assessed during an experiment. Hydration, bo dy temperature, movement and position of the animal in the device affect ac curacy. Thus, it was felt that if an animal died during an experiment, its body composition could not be measured as were live animals because of chan ges in body temperature. We found that carcasses of animals previously froz en could be analyzed by the EM-SCAN with similar accuracy to determinations made on live animals. However, calibration curves are different.