Nitrogen Requirement of the Omnivorous Greater Bilby,Macrotis lagotis(Marsupialia: Peramelidae)

Mainly due to their utilisation of relatively low‐fiber diets compared to herbivorous mammals, omnivores are expected to have correspondingly low maintenance nitrogen requirements (MNRs). The limited studies examining nitrogen requirements of omnivorous mammals to date have shown this to be the case...

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Bibliographic Details
Published in:Physiological and biochemical zoology 2002-01, Vol.75 (1), p.48-56
Main Authors: Gibson, L. A., Hume, I. D.
Format: Article
Language:English
Subjects:
Amino acids
Animal Nutritional Physiological Phenomena
Animal physiology
Animals
Diet
Feces - chemistry
Female
Food Analysis
Male
Marsupialia - metabolism
Marsupialia - physiology
Marsupials
Nitrogen
Nitrogen - metabolism
Nitrogen - urine
Nitrogen balance
Nutritional Requirements
Omnivores
Opossums
Recycling
Seeds
Species Specificity
Urine
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Summary:Mainly due to their utilisation of relatively low‐fiber diets compared to herbivorous mammals, omnivores are expected to have correspondingly low maintenance nitrogen requirements (MNRs). The limited studies examining nitrogen requirements of omnivorous mammals to date have shown this to be the case. In this article, we determine the dietary MNR of greater bilbies (Macrotis lagotis), arid‐zone omnivorous marsupials, by feeding them varying proportions of mixed seeds and dried currants (sun‐dried grapes). We also examine the possibility that bilbies conserve nitrogen by recycling endogenous urea to their gastrointestinal tract. The dietary MNR of 127 mg N kg−0.75d−1calculated for the bilby falls within the range calculated for other marsupial omnivores and is lower than that of any of the herbivores. This low requirement for nitrogen was correlated with significant recycling of endogenous urea to the gut; bilbies recycled between 44% and 80% of urea synthesised in the liver, but the proportion recycled was independent of dietary nitrogen intake. The relatively low MNR of the bilby is consistent with its low rates of basal metabolism and the recycling of endogenous urea to the gut, both of which reduce urinary nitrogen losses, and a low‐fiber diet that minimises metabolic fecal nitrogen loss. Because the bilby inhabits an environment where its food supply is unpredictable and of seasonally low nitrogen content, this species is likely to benefit from its low requirement for nitrogen.
ISSN:1522-2152
1537-5293
DOI:10.1086/338282