title: Digestive physiology, metabolism and methane production of captive Linné's two-toed sloths (Choloepus didactylus).
abstract: Sloths are renowned for their low metabolic rate, low food intake and low defecation frequency. We investigated factors of digestive physiology and energy metabolism in four captive individuals (mean body mass 10.0 ± SD 3.7 kg) of a hitherto mostly unstudied sloth species, Linné's two-toed sloth (Choloepus didactylus), in a 2-week digestion recording and 23-h respiration experiment on animals fed a standard zoo diet of vegetables and starchy components. Dry matter intake, defecation frequency and particle mean retention time (MRT) in the gastrointestinal tract (GIT) were 12 ± 3 g/(kg(0.75)  day), once every 5 days and >140 h in three individuals, but 53 g/(kg(0.75)  day), daily and 82 h in one individual that was apparently compensating for a period of weight loss prior to the experiment. In all animals, solute marker was eliminated at a faster rate than the particle marker, indicating 'digesta washing' in the sloths' GIT. The overall metabolic rate calculated from oxygen consumption matched the metabolisable energy intake in three individuals [173 ± 22 vs. 168 ± 44 kJ/(kg(0.75)  day)] but not in the fourth one [225 vs. 698 kJ/(kg(0.75)  day)], supporting the interpretation that this animal was replenishing body stores. In spite of the low food intake and the low-fibre diet (209 ± 26 g neutral detergent fibre/kg dry matter), methane production was rather high accounting for 9.4 ± 0.8% of gross energy intake (2.7% in the fourth individual), which exceeded literature data for ruminants on forage-only diets. These results corroborate literature reports on low intake, low defecation frequency, low metabolic rate and long MRT in other sloth species. The long MRT is probably responsible for the comparatively high methane production, providing more opportunity for methanogenic archaea than in other non-ruminant mammals to produce significant amounts of methane.
authors.affiliation: Clinic for Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
authors.forename: C
authors.initials: C
authors.lastname: Vendl
authors.affiliation: Clinic for Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
authors.forename: S
authors.initials: S
authors.lastname: Frei
authors.affiliation: Clinic for Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.|ETH Zurich, Institute of Agricultural Sciences, Zurich, Switzerland.
authors.forename: M T
authors.initials: MT
authors.lastname: Dittmann
authors.affiliation: Zoo Zurich, Zurich, Switzerland.
authors.forename: S
authors.initials: S
authors.lastname: Furrer
authors.affiliation: Zoo Dortmund, Dortmund, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Osmann
authors.affiliation: Leibniz Institute for Zoo and Wildlife Research (IZW), Berlin, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Ortmann
authors.affiliation: School of Biological Sciences, University of Wollongong, Wollongong, NSW, Australia.
authors.forename: A
authors.initials: A
authors.lastname: Munn
authors.affiliation: ETH Zurich, Institute of Agricultural Sciences, Zurich, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Kreuzer
authors.affiliation: Clinic for Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Clauss
mesh_terms: D000818:Animals; D000836:Animals, Zoo; D004063:Digestion / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D008297:Male; D008697:Methane / Q000096:biosynthesis*; D012896:Sloths / Q000502:physiology*
chemical_list: D008697:Methane
keywords: Pilosa; acetoclastic archaea; digestibility; enteric methanogenesis; folivora; foregut; xenarthra