Response of roe deer (Capreolus capreolus) to seasonal and local changes in dietary energy content and quality

Context: In terms of their nutritional physiology, roe deer have been called 'concentrate selectors'. This implies that they select proteins in their diet and are not able to digest fibre. It is, thus, suggested that in an agricultural landscape, they are unable to digest the high fibre content of arable crops and, thus, suffer and need to be given supplementary feed. Aims: Our aim was to determine the nutrient composition and energy content of the roe deer diet in an agricultural habitat compared with that in a natural forest habitat. Methods: Rumen contents of 245 roe deer were collected to represent each month of the year for 3 years, weighed, and analysed by standard methods for nutrient and fibre content. Key results: Roe deer in the agricultural habitat had rumen contents with significantly higher metabolisable energy (ME) concentrations, with a median of 6.2 MJ ME/kg DM, than did roe deer in the forest habitat, where the median was 5.4 MJ ME/kg DM. The mass of rumen contents in the forest habitat was, on average, 240 g higher than that in the agricultural habitat. Roe deer in the forest habitat compensate for the lower energy concentration in their natural diet by increasing their food intake. The concentration in the agricultural habitat is a result of the higher proportion of easily digestible carbohydrates in the diet. The concentration of crude protein in the rumen contents did not differ statistically between the two areas. In both habitats, the mean crude fibre concentration varied between 24% DM and 34% DM, and was significantly higher in the forest. The concentration of crude fibre selected by the roe deer is similar to the concentration of crude fibre known to be selected by red deer and fallow deer (intermediate feeders) and mouflon (a grazer) (Hofmann 1989). Conclusions: The term 'concentrate selector' should be replaced by 'selector' to avoid misinterpretations. Energy shortfalls were not observed in either of the populations during the study period. Implications: Supplemental feeding was not necessary to maintain the population.