Validation of two new total body electrical conductivity (TOBEC) instruments for estimating body composition of live northern red-backed voles Clethrionomys rutilus

Abstract

. 1997. Validation of two new total body electrical conductivity (TOBEC) instruments for estimating body composition of live northern red-backed voles Clethrionomys rutilus. Acta Theriologica 42: 387-397.Total body electrical conductivity (TOBEC) is a method for non-destructively estimating body composition. We sought to monitor seasonal changes in total body fat in northern red-backed voles Clethrionomys rutilus (Pallas, 1779), a microtine (10-45 g). We validated two new TOBEC instruments: the SA-3000 by EM-SCAN Inc. and the ACAN-2 by Jagmar Inc. Both instruments explained 94% of the variation in lean body mass and total body water. However, accuracy of fat estimates generated from lean mass predictions was poor for both instruments (± > 100%). Two instrument-specific multiple regression models and a TOBEC-free multiple regression model were used to estimate total body fat. All three improved the ability to predict total body fat in C. rutilus. These two TOBEC instruments can not be used to measure changes in total body fat of individual C. rutilus due to the small amount of fat reserves and lack of seasonal variation.

Evaluation of the TOBEC Method for Calculating Fat Mass in Tree SparrowsPasser montanusand House SparrowsPasser domesticus

“…Similar procedures have been applied in the measurement of much larger birds (Calidris pusilla, C. fuscicollis), with similar results being obtained (Skagen et al 1993). Besides means of readings from repeated measurements, minimal values have also been taken into consideration (Zuercher et al 1997). As our calculations show, these are better correlated with lean body mass than maximal values (Table 3).…”

“…Conway et al (1994), working on the Wood Thrush Hylocichla mustelina, repeated TOBEC measurements 16 times, and recommended that an average of 9 measurements be made. Roby et al (1997), and Zuercher et al (1997), applied 6 repetitions of TOBEC measurements, while Burger (1997) used 7 measurements per bird. It was possible to conclude from the latter that a TOBEC measurement of the same individual is of limited repeatability irrespective of species and type of apparatus used.…”

“…All were weighed to an accuracy of 0.01 g using electronic balances, measured for tarsus length to an accuracy of 0.1 mm and then subjected to TOBEC measurement using the ACAN-2 apparatus. This apparatus -operating on the basis of the TOBEC method -was constructed by Techmex International of Kraków (Poland), in co-operation with the Department of Biophysics of the Jagiellonian University (Froncisz et al 1994, Piasecki et al 1995, Koteja 1996, Zuercher et al 1997). Indications of TOBEC may be compared with LBM without transformation.…”

“…However, because it allowed for estimates of amounts of fat in live vertebrates, it soon found application in scientific research on: human adult males (Presta et al 1983a, b) and infants (Cochran et al 1989), pigs (Fiorotto et al 1987, Cochran et al 1989), rabbits (Fiorotto et al 1987), rodents (Bracco et al 1983, Piasecki et al 1995, Koteja 1996, Zuercher et al 1997, fish (Fisher et al 1996) and birds (Walsberg 1988, Castro et al 1990, Morton et al 1991, Roby 1991, Scott et al 1991, Skagen et al 1993, Conway et al 1994, Asch & Roby 1995, Lyons & Haig 1995, Staudinger et al 1995, Burger 1997.…”

“…In animals with small amounts of fat these errors may reach 200% of real fat mass (Skagen et al 1993, Conway et al 1994, Zuercher et al 1997. However, in such cases it is possible to make intraspecific comparisons using the TOBECestimated mean fat mass of an appropriately-large group of animals, especially where individuals in these groups do not differ in mean body mass.…”