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Phylogenetic constraints on digesta separation: Variation in fluid throughput in the digestive tract in mammalian herbivores


Müller, D W H; Caton, J; Codron, D; Schwarm, A; Lentle, R; Streich, W J; Hummel, J; Clauss, Marcus (2011). Phylogenetic constraints on digesta separation: Variation in fluid throughput in the digestive tract in mammalian herbivores. Comparative Biochemistry and Physiology - Part A: Molecular and Integrative Physiology, 160(2):207-220.

Abstract

The relevance of the mean retention time (MRT) of particles through the gastrointestinal tract (GIT) is well understood and MRTparticleGIT is an important parameter in digestion models. Solute markers have been used to estimate MRTsoluteGIT (or ‘fluid passage’) in animals, but the relevance of this measure is less evident and is usually sought in its relation to MRTparticleGIT. The ratio between the two measures indicates the degree of ‘digesta washing’, with little washing occurring at ratios of 1, aborad washing at ratios N1 (where the solute marker travels faster than the particle marker), and orad (retrograde) washing at ratios b1 (where the solute marker travels slower than the particle marker). We analysed digesta washing in a dataset of 98 mammalian species including man of different digestion types (caecum, colon and nonruminant foregut fermenters, and ruminants), controlling for phylogeny; a subset of 72 species allowed testing for the influence of food intake level. The results indicate that MRTsoluteGIT and the degree of digesta washing are related to digestion type, whereas variation in MRTparticleGIT is influenced mainly by effects of body mass and food intake. Thus, fluid throughput and digesta washing emerge as important correlates of digestive anatomy. Most importantly, primates appear constrained to little digesta washing compared to non-primate mammalian herbivores, regardless of their digestion type. These results may help explain the absence of primates from certain herbivore niches and represent a drastic example of a physiologic limitation in a phylogenetic group. Moreexperimental research is required to illuminate relative benefits and costs of digesta washing.

Abstract

The relevance of the mean retention time (MRT) of particles through the gastrointestinal tract (GIT) is well understood and MRTparticleGIT is an important parameter in digestion models. Solute markers have been used to estimate MRTsoluteGIT (or ‘fluid passage’) in animals, but the relevance of this measure is less evident and is usually sought in its relation to MRTparticleGIT. The ratio between the two measures indicates the degree of ‘digesta washing’, with little washing occurring at ratios of 1, aborad washing at ratios N1 (where the solute marker travels faster than the particle marker), and orad (retrograde) washing at ratios b1 (where the solute marker travels slower than the particle marker). We analysed digesta washing in a dataset of 98 mammalian species including man of different digestion types (caecum, colon and nonruminant foregut fermenters, and ruminants), controlling for phylogeny; a subset of 72 species allowed testing for the influence of food intake level. The results indicate that MRTsoluteGIT and the degree of digesta washing are related to digestion type, whereas variation in MRTparticleGIT is influenced mainly by effects of body mass and food intake. Thus, fluid throughput and digesta washing emerge as important correlates of digestive anatomy. Most importantly, primates appear constrained to little digesta washing compared to non-primate mammalian herbivores, regardless of their digestion type. These results may help explain the absence of primates from certain herbivore niches and represent a drastic example of a physiologic limitation in a phylogenetic group. Moreexperimental research is required to illuminate relative benefits and costs of digesta washing.

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Item Type:Journal Article, refereed, original work
Communities & Collections:05 Vetsuisse Faculty > Veterinary Clinic > Department of Small Animals
Dewey Decimal Classification:570 Life sciences; biology
630 Agriculture
Language:English
Date:2011
Deposited On:27 Jul 2011 12:15
Last Modified:11 Sep 2016 07:27
Publisher:Elsevier
ISSN:1095-6433
Publisher DOI:https://doi.org/10.1016/j.cbpa.2011.06.004
PubMed ID:21689778

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