title: The Nutritional Balancing Act of a Large Herbivore: An Experiment with Captive Moose (Alces alces L).
abstract: The nutrient balancing hypothesis proposes that, when sufficient food is available, the primary goal of animal diet selection is to obtain a nutritionally balanced diet. This hypothesis can be tested using the Geometric Framework for nutrition (GF). The GF enables researchers to study patterns of nutrient intake (e.g. macronutrients; protein, carbohydrates, fat), interactions between the different nutrients, and how an animal resolves the potential conflict between over-eating one or more nutrients and under-eating others during periods of dietary imbalance. Using the moose (Alces alces L.), a model species in the development of herbivore foraging theory, we conducted a feeding experiment guided by the GF, combining continuous observations of six captive moose with analysis of the macronutritional composition of foods. We identified the moose's self-selected macronutrient target by allowing them to compose a diet by mixing two nutritionally complementary pellet types plus limited access to Salix browse. Such periods of free choice were intermixed with periods when they were restricted to one of the two pellet types plus Salix browse. Our observations of food intake by moose given free choice lend support to the nutrient balancing hypothesis, as the moose combined the foods in specific proportions that provided a particular ratio and amount of macronutrients. When restricted to either of two diets comprising a single pellet type, the moose i) maintained a relatively stable intake of non-protein energy while allowing protein intakes to vary with food composition, and ii) increased their intake of the food item that most closely resembled the self-selected macronutrient intake from the free choice periods, namely Salix browse. We place our results in the context of the nutritional strategy of the moose, ruminant physiology and the categorization of food quality.
authors.affiliation: Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences, Alnarp, Sweden.
authors.forename: Annika M
authors.initials: AM
authors.lastname: Felton
authors.affiliation: Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences, Alnarp, Sweden.
authors.forename: Adam
authors.initials: A
authors.lastname: Felton
authors.affiliation: School of Biological Science and The Charles Perkins Centre, the University of Sydney, Sydney, New South Wales, Australia.|Faculty of Veterinary Science, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Raubenheimer
authors.affiliation: School of Biological Science and The Charles Perkins Centre, the University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Simpson
authors.affiliation: Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences, Umeå, Sweden.
authors.forename: Sophie J
authors.initials: SJ
authors.lastname: Krizsan
authors.affiliation: Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences, Alnarp, Sweden.
authors.forename: Per-Ola
authors.initials: PO
authors.lastname: Hedwall
authors.affiliation: Department of Animal Ecology and Conservation, Biocenter Grindel, University of Hamburg, Hamburg, Germany.
authors.forename: Caroline
authors.initials: C
authors.lastname: Stolter
mesh_terms: D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D003670:Deer / Q000502:physiology*; D004032:Diet; D004044:Dietary Proteins / Q000378:metabolism; D002149:Energy Intake; D005260:Female; D060434:Herbivory; D008297:Male; D008954:Models, Biological; D009752:Nutritional Status
chemical_list: D004044:Dietary Proteins