This study was to investigate the validity of energy measurement system by using different body size and sex of rats and feed supplementation methods. There appeared no statistical differences in energy(AME, AMEn) utilization between male and female rats with average 200g body weight, and between male rat of 200g and 300g body weight. Glucose replacing corn in the basal diet or replacing diet itself at a level of 30% by weight appeared to have the same metabolizable energy value, suggesting that either methods to supplement test ingredient brought about the same results. Consequently, following suggestions could be made from results of present study : first, Sprague-Dawley rate of either sex weighing 200-300g may be used as an animal model to obtain in vivo metabolizable energy from dietary carbo-hydrates or sea foods. Second, the testing ingredients may be added at the expence of corn in the basal diet at 30% level.