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Comparative methane emission by ratites: differences in food intake and digesta retention level out methane production


Frei, Samuel; Hatt, Jean-Michel; Ortmann, Sylvia; Kreuzer, Michael; Clauss, Marcus (2015). Comparative methane emission by ratites: differences in food intake and digesta retention level out methane production. Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology, 188:70-75.

Abstract

Ratites differ in the anatomy of their digestive organs and their digesta excretion patterns. Ostriches (Struthio camelus) have large fermentation chambers and long digesta retention, emus (Dromaius novaehollandiae) have a short gut and short retention times, and rheas (Rhea americana) are intermediate. A recent study showed that ostriches produce as much methane (CH4) as expected for a similar-sized, non-ruminant mammalian herbivore. We hypothesized that emus and rheas produce less CH4 than ostriches. We individually measured, by chamber respirometry, the amount of O2 consumed as well as CO2 and CH4 emitted from six adult rheas (body mass 23.4 ± 8.3 kg) and two adult emus (33.5 and 32.0 kg) during 23-hour periods on a pelleted lucerne diet. In contrast to previous studies, which classified emus as non-producers, we measured CH4 emissions at 7.39 and 6.25 L/day for emus and 2.87 ± 0.82 L/day for rheas, which is close to values expected for similar-sized non-ruminant mammals for both species. O2 consumption was of a similar magnitude as reported previously. Across ratites CH4 yield (L/kg dry matter intake) was positively correlated with mean retention time of food particles in the gut, similar to findings within ruminant species. In ratites, this relationship leads to similar body mass-specific CH4 production for a high intake/short retention and a low intake/long retention strategy. Therefore, when investigating CH4 production in herbivorous birds, it is advisable to consider various CH4 measures, not only yield or absolute daily amount alone.

Abstract

Ratites differ in the anatomy of their digestive organs and their digesta excretion patterns. Ostriches (Struthio camelus) have large fermentation chambers and long digesta retention, emus (Dromaius novaehollandiae) have a short gut and short retention times, and rheas (Rhea americana) are intermediate. A recent study showed that ostriches produce as much methane (CH4) as expected for a similar-sized, non-ruminant mammalian herbivore. We hypothesized that emus and rheas produce less CH4 than ostriches. We individually measured, by chamber respirometry, the amount of O2 consumed as well as CO2 and CH4 emitted from six adult rheas (body mass 23.4 ± 8.3 kg) and two adult emus (33.5 and 32.0 kg) during 23-hour periods on a pelleted lucerne diet. In contrast to previous studies, which classified emus as non-producers, we measured CH4 emissions at 7.39 and 6.25 L/day for emus and 2.87 ± 0.82 L/day for rheas, which is close to values expected for similar-sized non-ruminant mammals for both species. O2 consumption was of a similar magnitude as reported previously. Across ratites CH4 yield (L/kg dry matter intake) was positively correlated with mean retention time of food particles in the gut, similar to findings within ruminant species. In ratites, this relationship leads to similar body mass-specific CH4 production for a high intake/short retention and a low intake/long retention strategy. Therefore, when investigating CH4 production in herbivorous birds, it is advisable to consider various CH4 measures, not only yield or absolute daily amount alone.

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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
Uncontrolled Keywords:Digestion; Fermentation; Herbivory; Methanogenesis
Language:English
Date:2015
Deposited On:16 Jul 2015 12:32
Last Modified:04 Nov 2017 00:10
Publisher:Elsevier
ISSN:1095-6433
Funders:SNF, Basler Stiftung für biologische Forschung
Publisher DOI:https://doi.org/10.1016/j.cbpa.2015.06.022
PubMed ID:26123777

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