February 15-18, 2009 Washington State Convention Center Seattle ...

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USING NEAR-INFRARED REFLECTANCE SPECTROSCOPY (NIRS) TO PREDICT THE
DIGESTIBLE PROTEIN AND ENERGY VALUE OF GRAIN INGREDIENTS WHEN FED TO
RAINBOW TROUT, Oncorhynchus mykiss - THE LUPIN CASE STUDY
Brett Glencross*, Wayne Hawkins, Peter Burridge, David Evans, Neil Rutherford, Peter McCafferty, Ken Dods
and Sofia Sipsas
Department of Fisheries
PO Box 20, North Beach
WA 6920, Australia
Brett.Glencross@fish.wa.gov.au
Over a five-year period, 10 separate digestibility experiments undertaken to examine the digestibility of protein and energy
from 136 different samples of lupin meal from either Lupinus angustifolius or L. luteus. Lupin samples were obtained from the
Australian National Lupin Breeding Program’s germplasm lines and selected on the basis of maximal crude protein variability
as assessed by existing crude protein NIRS calibrations. Chemically measured crude protein values varied from 232 to 613 g/kg
DM. Gross energy values ranged from 18.7 to 21.6 MJ/kg DM. Other compositional parameters assessed included amino acids,
total lipids, ash, total carbohydrates, cellulose, hemicellulose and lignin.
The digestibility of protein and energy was assessed using the diet-replacement ingredient assessment method, where the test
ingredient comprised 30% of each test diet. Digesta was collected using faecal stripping techniques. Digestible protein values
ranged from 193 to 595 g/kg DM and digestible energy values ranged from 6.0 to 17.7 MJ/kg DM. The digestible protein and
energy values were then assessed using multiple regression techniques to determine which compositional parameters accounted
for the majority of the variability. Crude protein content was observed to be the most dominant single factor in affecting digestible
protein levels. However, multiple regression analysis supported that protein and lignin content combined were the strongest
predictors of digestible protein value, explaining close to 60% of the variability in this parameter. Digestible energy values
were hevily reflective of the factors influencing digestible protein value. This study demonstrates that within one raw material
type that not only does significant variability in the digestible value of the raw materials exist, but that it is possible to identify
compositional features of that raw material that are intrinsically influencing its own digestible value. Predictive equations have
been developed that explain this variability.
Assessment of these samples using near-infrared spectroscopy (NIRS) shows that there are certain wavelengths that correlate
with crude protein and lignin content of the lupin kernel meals. Applying a dual assessment to both of these parameters, based
on the predetermined relationship, it has been possible to develop a calibration to predict both digestible protein and energy
content of lupin kernel meals. This calibration can now be used to assess lupin meals prior to formulation to minimise digestible
protein and energy content of diets in which they are included.