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Near infrared spectroscopy predictions on heterogeneous databases : an example of plants from sub-alpine meadows and shrublands

Lembke M., Bastianelli D., Dobremez J.F., Hervouet C., Bonnal L., Maillard D.. 2007. In : Burling-Claridge G.R. (ed.), Holroyd S.E. (ed.), Sumner R.M.W. (ed.). Near infrared spectroscopy : Proceedings of the 12th International Conference, Auckland, New Zealand, 9th - 15th April 2005. Chichester : IM Publications, p. 99-100. International Conference on Near Infrared Spectroscopy. 12, 2005-04-09/2005-04-15, Auckland (Nouvelle-Zélande).

The aim of this study was to describe the diet habitat of a mountain ungulate species: Capra i. ibex through the vegetation characteristics. The sub-alpine vegetation is composed by a great number of species that forms a heterogeneous cover. This cover constitutes a great variable diet resource for ibex. An analysis for all species forming the plant cover was impossible, as there are 91 determined species. Moreover there is only a relative knowledge of the diet selection of the ibex in the study site, so the approach is to assess nutritional quality of the plant cover as a whole through it chemical composition. Plant samples from various places throughout the study zone were collected during 2 years, resulting in nearly 500 samples. Samples were dried, ground and spectra in diffuse reflectance were measured on a FOSS NIRSystem 6500 spectrometer in small ring cups. Chemical analysis of samples was performed on 150-200 samples selected for their spectral representativeness of the whole database: the parameters measured were Crude Protein (CP), Acid Detergent Lignin (ADL) and in vitro organic matter digestibility (OMD). Calibration equations were built after mathematical pre-processing of data (SNV and detrend with 2nd derivative of spectra). Partial Least Squares regression (modified PLS in WINISI software) was found to be the most efficient method for calibrations. General equations had SECV values of 0.52% for CP, 1.37% for ADL and 2.73% for OMD, leading to RPD (=SD/SECV) values of 7.7, 6.1 and 5.2 respectively. However the choice of computing general equations can be questioned since plant covers can be roughly split into 2 categories: herbaceous (HB) or shrubby (SH), which differ strongly in term of chemical composition and nutritional value. Therefore it was decided to test different equations for each of these categories. Samples were affected to a category on the basis of their known botanical composition. However a part of samples could not be classified a pri

Mots-clés : habitat; régime alimentaire; chèvre; végétation alpine; composition chimique

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