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Evidence for a tradeoff between retention time and chewing efficiency in large mammalian herbivores


Clauss, Marcus; Nunn, C; Fritz, J; Hummel, J (2009). Evidence for a tradeoff between retention time and chewing efficiency in large mammalian herbivores. Comparative Biochemistry and Physiology - Part A: Molecular and Integrative Physiology, 154(3):376-382.

Abstract

Large body size is thought to produce a digestive advantage through different scaling effects of gut capacity and food intake, with supposedly longer digesta retention times in larger animals. However, empirical tests of this framework have remained equivocal, which we hypothesize is because previous comparative studies have not included digesta particle size. Larger particles require more time for digestion, and if digesta particle size increases with body mass, it could explain the lack of digestive advantage in larger herbivores. We combine data on body mass, food intake, digesta retention and digestibility with data on faecal particle size (as a proxy for digesta particle size) in 21 mammalian herbivore species. Multiple regression shows that fibre digestibility is independent of body mass but dependent on digesta retention and particle size; the resulting equation indicates that retention time and particle size can compensate for each other. Similarly, digestible food intake is independent of body mass, but dependent on food intake, digesta retention, and particle size. For mammalian herbivores, increasing digesta retention and decreasing digesta particle size are viable strategies to enhance digestive performance and energy intake. Because the strategy of increased digesta retention is usually linked to reduced food intake, the high selective pressure to evolve a more efficient dentition or a physiological particle separation mechanism that facilitates repeated mastication of digesta (rumination) becomes understandable.

Abstract

Large body size is thought to produce a digestive advantage through different scaling effects of gut capacity and food intake, with supposedly longer digesta retention times in larger animals. However, empirical tests of this framework have remained equivocal, which we hypothesize is because previous comparative studies have not included digesta particle size. Larger particles require more time for digestion, and if digesta particle size increases with body mass, it could explain the lack of digestive advantage in larger herbivores. We combine data on body mass, food intake, digesta retention and digestibility with data on faecal particle size (as a proxy for digesta particle size) in 21 mammalian herbivore species. Multiple regression shows that fibre digestibility is independent of body mass but dependent on digesta retention and particle size; the resulting equation indicates that retention time and particle size can compensate for each other. Similarly, digestible food intake is independent of body mass, but dependent on food intake, digesta retention, and particle size. For mammalian herbivores, increasing digesta retention and decreasing digesta particle size are viable strategies to enhance digestive performance and energy intake. Because the strategy of increased digesta retention is usually linked to reduced food intake, the high selective pressure to evolve a more efficient dentition or a physiological particle separation mechanism that facilitates repeated mastication of digesta (rumination) becomes understandable.

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Additional indexing

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:November 2009
Deposited On:25 Sep 2009 06:38
Last Modified:05 Oct 2016 07:33
Publisher:Elsevier
ISSN:1095-6433
Publisher DOI:https://doi.org/10.1016/j.cbpa.2009.07.016

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