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RESEARCH ARTICLE
Contents Vol 32(4)

Validation of the n-alkane technique for estimating diet composition, digestibility and dry matter intake in the brushtail possum (Trichosurus vulpecula)

Adrian Monks A C , Ian Payton B and Murray Efford A
+ Author Affiliations
- Author Affiliations

A Landcare Research, Private Bag 1930, Dunedin, New Zealand.

B Landcare Research, PO Box 69, Lincoln, New Zealand.

C Corresponding author. Email: monksa@landcareresearch.co.nz

Wildlife Research 32(4) 321-331 https://doi.org/10.1071/WR04030
Submitted: 22 April 2004  Accepted: 19 April 2005   Published: 5 July 2005

Abstract

Few validated studies have tested the n-alkane method for diet estimation in non-ruminants and the technique has rarely been validated for estimating diet composition for more than two dietary components. The arboreal marsupial Trichosurus vulpecula was fed leaf and fruit diets with up to five component species in two trials. In Trial 1, alkane recovery was estimated, and in Trial 2 these estimates were used to predict digestibility, diet composition and dry matter intake. Alkane recovery increased non-linearly (convex up) with increasing n-alkane chain length. Recovery was linearly and negatively correlated with diet digestibility and appeared to explain a progressive bias with observed digestibility in the alkane estimates of digestibility (slope = 0.37). Diet composition was successfully estimated for up to five leaf dietary components without correction for recovery. Correcting for recovery gave less reliable diet-composition predictions, indicating that the recovery estimates could not be extrapolated to the second trial. Dry matter intake appeared to be relatively robust to variation in alkane recovery between individuals (mean bias =1.6%). If recovery is shown to vary with digestibility in other taxa, calibration of the alkane technique will require diet- and taxon-specific calibration trials to give reliable estimates of diet composition and dry matter digestibility.


Acknowledgments

We are grateful to Esther Sibbald for help in collecting and preparing the leaf material. Lara Nicholson helped tirelessly pressing pellets and with various preliminary palatability work. Thanks also to Jeanne Kuhajek and Les Brown for help in the preparation of the marker pellets. Julie Turner, Karen Washbourne and Mike Wehner provided assistance at the Landcare Research Animal Facility. Dexcel NZ conducted the alkane assays. Hugh Dove, Graham Nugent and Christine Bezar made valuable comments on an earlier draft of the manuscript. We thank the various landowners who allowed us to collect plant material, including Dunedin City Council, Cityforests Ltd and Ian Woodrow. This study was approved by the Landcare Research Animal Ethics Committee (Approval No. 02/06/02).


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