title: Contrary seasonal changes of rates of nutrient uptake, organ mass, and voluntary food intake in red deer (Cervus elaphus).
abstract: Northern ungulates acclimatize to winter conditions with restricted food supply and unfavorable weather conditions by reducing energy expenditure and voluntary food intake. We investigated in a study on red deer whether rates of peptide and glucose transport in the small intestines are also reduced during winter as part of the thrifty phenotype of winter-acclimatized animals, or whether transport rates are increased during winter in order to exploit poor forage more efficiently. Our results support the latter hypothesis. We found in a feeding experiment that total energy intake was considerably lower during winter despite ad libitum feeding. Together with reduced food intake, mass of visceral organs was significantly lower and body fat reserves were used as metabolic fuel in addition to food. However, efficacy of nutrient absorption seemed to be increased simultaneously. Extraction of crude protein from forage was higher in winter animals, at any level of crude protein intake, as indicated by the lower concentration of crude protein in feces. In line with these in vivo results, Ussing chamber experiments revealed greater electrogenic responses to both peptides and glucose in the small intestines of winter-acclimatized animals, and peptide uptake into jejunal brush-border membrane vesicles was increased. We conclude that reduced appetite of red deer during winter avoids energy expenditure for unproductive search of scarcely available food and further renders the energetically costly maintenance of a large gut and visceral organs unnecessary. Nevertheless, extraction of nutrients from forage is more efficient in the winter to attenuate an inevitably negative energy balance.
authors.affiliation: Research Institute of Wildlife Ecology, Department of Integrative Biology and Evolution, University of Veterinary Medicine, Vienna, Vienna, Austria; and walter.arnold@vetmeduni.ac.at.
authors.forename: Walter
authors.initials: W
authors.lastname: Arnold
authors.affiliation: Research Institute of Wildlife Ecology, Department of Integrative Biology and Evolution, University of Veterinary Medicine, Vienna, Vienna, Austria; and.
authors.forename: Christoph
authors.initials: C
authors.lastname: Beiglböck
authors.affiliation: Institute of Physiology, University of Veterinary Medicine, Hannover, Germany.
authors.forename: Marion
authors.initials: M
authors.lastname: Burmester
authors.affiliation: Institute of Physiology, University of Veterinary Medicine, Hannover, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Guschlbauer
authors.affiliation: Research Institute of Wildlife Ecology, Department of Integrative Biology and Evolution, University of Veterinary Medicine, Vienna, Vienna, Austria; and Institute of Physiology, University of Veterinary Medicine, Hannover, Germany.
authors.forename: Astrid
authors.initials: A
authors.lastname: Lengauer
authors.affiliation: Institute of Physiology, University of Veterinary Medicine, Hannover, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Schröder
authors.affiliation: Institute of Physiology, University of Veterinary Medicine, Hannover, Germany.
authors.forename: Mirja
authors.initials: M
authors.lastname: Wilkens
authors.affiliation: Institute of Physiology, University of Veterinary Medicine, Hannover, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Breves
mesh_terms: D000818:Animals; D001066:Appetite / Q000502:physiology; D003670:Deer / Q000502:physiology*; D004435:Eating / Q000502:physiology*; D002149:Energy Intake / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology*; D005247:Feeding Behavior; D012621:Seasons
keywords: active transport; glucose transport; nutrients; peptide transport; seasonal acclimatization