Developing NIRS calibrations to predict the nutritional value of Russell lupin (Lupinus Polyphyllus)

Abstract

Short paper-Russell lupin (Lupinus polyphyllus) has proven to be a persistent pasture legume in high country environments in the South Island of NZ (Scott, 1989). However its feed value for livestock has had little previous quantification (Kitessa et al., 1993; Scott et al., 1994). A new project carried out by Lincoln University is evaluating Russell lupin for Merino sheep and feed analyses are required to determine its nutrient ingredients. Because traditional analytical methods that rely on wet chemistry are time consuming and costly. By developing NIRS calibrations for Russell lupin, we will be able to estimate its forage quality in a cost-effective and timely manner.

129 samples of Russell lupin, collected from Sawdon Station, Tekapo, oven dried and grounded, were used to develop calibration models to predict crude protein (CP), carbon (C), digestibility (DMD), acid detergent fibre (ADF), neutral detergent fibre (NDF), residual matter (rDM), organic matter (OM) and water soluble carbohydrate (WSC) content. They included samples of lamina, petioles, stems and flowers of lupin plants. 98 samples were used for the build-up calibration equation, and 28 samples were selected as a validation set. Corresponding reference values were determined by traditional laboratory analysis. A Foss NIRSystems 5000 spectrometer was used for sample scan and WinISI IV for model simulation.

The calibration models were developed using Modified PLS (Partial Least Squares). Different scatter correction and derivation methods were compared in order to allow the PLS algorithm to find the best correlation between the spectral data and concentrations. The evaluation of the model was undertaken using SEC, RSQ, SECV and 1-VR values (Table 1). The monitor statistics SEP and RSQ for the validation set were also taken into consideration. This NIRS calibration equation can serve as a quick alternative method for the determination of nutrient ingredients for Russell lupin. However, the equation needs to be refined with more lupin samples to improve its performance.