Data for: Ingredient and nutrient composition of brown bear diets

The dietary nutrient profile has metabolic significance and possibly
contributes to species’ foraging behavior. The brown bear (Ursus arctos)
was used as a model species for which dietary ingredient and nutrient
concentrations as well as nutrient ratios were determined annually,
seasonally and per reproductive class. Brown bears had a vertebrate- and
ant-dominated diet in spring and early summer and a berry-dominated diet
in fall, which translated into protein-rich and carbohydrate-rich diets,
respectively. Fiber concentrations appeared constant over time and
averaged at 25 % of dry matter intake. Dietary ingredient proportions
differed between reproductive classes; however, these differences did not
translate into a difference in dietary nutrient concentrations, suggesting
that bears manage to maintain similar nutrient profiles with selection of
different ingredients. In terms of nutrient ratios, the dietary protein to
non-protein ratio, considered optimal at around 0.2 (on metabolizable
energy basis), averaged around 0.2 in this study in fall and around 0.8 in
spring and summer. We introduced the minimal non-fat to fat ratio
necessary for efficient maintenance metabolism. This ratio varied across
seasons but never fell beneath the theoretically estimated minimum to
ensure metabolic efficiency. This population thus managed to ingest diets
that never exerted a lack of glucogenic substrate, suggesting that
metabolic efficiency may either be a driver of active diet selection or
that natural resources available to bears did not constitute a constraint
in this respect. Given the considerable proportion of fiber in the diet of
brown bears, the relevance of this nutrient and its role in foraging
behavior might be underestimated.