Study of body composition in small animals by a multifrequency impedancemeter

Bioimpedance is essentially used today to study the body composition in the human body but not really in small animals. The aim of this paper is to develop a model for body composition in rats to help pharmaceutical labs assessing effects of medicine on rats. We propose a non invasive, rapid and scientific method. With a multifrequency impedancemeter, Z-Metrix® (BioparHom© Company France), resistances and reactances are measured at 55 frequencies for a population of 40 rats (males and females). With our model, derived from Cole-Cole model, resistances of extracellular (Re) and total body (Rinf) compartment are extrapolated. Three methods were applied: posterior to posterior leg, anterior to posterior leg on the left and on the right side. Measurements by CT imaging were performed on the anesthetized population to determine Fat Mass (FM), Lean Body Mass (LBM) and Bone Mineral Content (BMC), as our reference measurements. With electrical data, age, sex and weight, equations are created to calculate FM, LBM and BMC with the three methods. Graphs of correlation, between tissue masses calculated by bioimpedance and obtained with scanner, indicate that measurements with posterior to posterior leg are better. Moreover, there is no significantly difference between tissue masses measured by bioimpedance and with the scanner.