Electrical conductivity to predict body composition of mammals and the effect of gastrointestinal contents

Abstract

We evaluated electrical conductivity to predict composition of live prairie voles (Microtus ochrogaster) with the Small Animal Body Composition Analyzer (EM-SCAN®, Inc.; Models SA-2 and SA-3044). By using both captive and field-caught voles, we examined the validity of predictive equations for animals that varied widely in their mass of lipid. The two-stage model predicted fat-free mass (and therefore mass of lipid) with an average error of 1.06 g for the Model SA-2 and 1.64 g for the SA-3044. This level of resolution was sufficient for estimating body composition of captive prairie voles with moderate-to-high levels of fat (5-14 g or 20% fat) but not for wild-caught voles, whose level of fat was much lower (1-3 g or 4% fat). We also examined effect of gastrointestinal contents on estimates of body composition provided by conductive measurements. We killed 15 voles and obtained measures of conductivity before and after injection of 5 g of food into the peritoneal cavity. Results showed that contents of the gastrointestinal tract were read in a manner indistinguishable from other fat-free components.