Comparative determinations of rat body composition by chemical, near infrared reflectance and total body electrical conductivity analyses.

Rat carcass characteristics were determined by classical chemical analyses, near infrared reflectance (NIR) and total body electrical conductivity (TOBEC), with the aim to establish a rapid, reliable and soft method for numerous body composition predictions. In order to get a wide range in rat carcass protein and fat contents, animals were fed ad libitum with a commercial diet supplemented with various doses of cimaterol, a beta 2-adrenergic agonist having repartitioning effects. Samples analyzed by chemical methods allowed a suitable NIR calibration for protein and fat rat carcass contents. Comparison of chemical and NIR predictions gave equal values for protein and fat determinations. A linear correlation (R = 0.974) could be defined between both parameters. Similarly, the comparison of rat fat content determined with NIR and TOBEC also showed a linear correlation (R = 0.984). These correlations allowed to calculate rat protein content, after TOBEC fat measurements, using the prediction equation established from the linear protein-fat correlation found after NIR analyses. Calculated and NIR measured protein content values had a correlation coefficient of 0.956. It was concluded, that for the experimental conditions and the animal strain used, TOBEC analyses showed the best qualities to meet the fixed goals. TOBEC appeared as a suitable noninvasive method for body composition determinations. Furthermore, the technique enables repeated measurements in living animals for kinetic evaluation studies.