Body condition assessment and prediction of fasting endurance in wild rabbits (Oryctolagus cuniculus)

Abstract

In many species, reproductive success, resistance to food shortage and immune response to parasitism depend on body nutrient reserves. Thus, determining body fuels is important for studying the impact of the environment on animal fitness. As an alternative to the usual biochemical methods, we have defined models for estimating body composition in rabbits (Oryctolagus cuniculus). The accuracy of the indices obtained on a source group was tested on an independent group. The models were applicable regardless of age, sex or season. The intact body mass already accounted for 90% of the protein variability. The most accurate equation combining dry body mass and interscapular fat mass explained 99% of the protein variations. Intact body mass and the kidney fat index were poor estimators of lipid stores (r2 = 0.45) but 90% of the variation was explained by an equation combining the interscapular fat mass and the hind leg length. None of the predictive equations significantly over- or underestimated body reserves. The usefulness of the models was assessed by estimating fasting endurance during winter. Individual estimates, ranging from two to eight days, did not differ by more than 0.5 day from the fasting endurance obtained from actual mobilisable body nutrients. In such lean species (adiposity 2–4%), proteins may account for up to 40% of the available energy reserves and survival is likely to be linked to the continuous availability of food resources. These results stress the need to determine proteins and not only lipids to have a pertinent tool for the management of wild animal populations, particularly in lean species.