A digestibility assessment of pearl lupin (Lupinus mutabilis) meals and protein concentrates when fed to rainbow trout (Oncorhynchus mykiss)

Two experiments were undertaken to examine the digestible value of a range of grain products produced from seed of the pearl lupin Lupinus mutabilis. These products were then evaluated against similar products produced from the lupin species L. angustifolius and L. luteus and solvent-extracted soybean meals. The value-added products were then included in diets at a 300 g/kg inclusion level to assess their apparent dry matter, protein and energy digestibilities. It was observed that L. mutabilis kernel meals had superior digestible value characteristics to that of L. angustifolius kernel meal and similar values to that of solvent-extracted soybean and L. luteus kernel meals. The use of solvent-extractive value-adding techniques only marginally increased the protein content of L. mutabilus kernel meal, but reduced their digestible energy value. A more significant increase in protein content was observed using aqueous extractive techniques, although this had mixed effects on the digestible value of the products. The use of protein isolation techniques substantially increased the protein content and digestible value of products produced from each of the species examined. This work demonstrates that grain from L. mutabilis seed can be effectively processed to produce meals that have digestible values potentially useful for aquaculture feeds.