Effects of enzyme supplementation on the nutritive value of dehulled lupins.

Abstract

1. Separate balance experiments were conducted to assess the potential of 2 commercial enzyme supplements to improve the nutritive value of dehulled lupin kernels. One supplement (enzyme A) contained primarily xylanase, pentosanase, hemicellulase activities and the other (enzyme B) primarily beta-glucanase, hemicellulase and pectinase activities. 2. The enzymes were added at 0, 0.25, 0.50, 0.75 and 1.00 g/kg in diets containing (g/kg) lupins 300, sorghum 543, casein 91, celite (as marker) 20, and vitamins and minerals 46. Control diets, with and without enzyme supplementation contained sorghum and casein at 800 and 134 g/kg, respectively, and no lupins. 3. Growth rates and food conversion ratios (FCR) of birds over 7 days were not affected by lupin inclusion or enzyme supplementation. FCR of broilers fed on the sorghum diet was improved by enzyme A but not by enzyme B. 4. Ileal starch digestibilities were slightly lower in birds fed on the lupin control diet (no enzyme) compared to the basal control diet. 5. Enzyme A increased the AME of the lupins from 10.01 MJ/kg DM to 11.65 MJ/kg DM when added at 0.5 g/kg. Higher rates of supplementation did not lead to further increases in AME values. 6. Enzyme A did not improve starch digestion in the diets but insoluble non-starch polysaccharides concentration in the digesta decreased (50.41-42.71 g/g acid insoluble ash marker) with increasing enzyme supplementation, suggesting that the improvement in AME was the result of increased fermentation of fibre in the hindgut. 7. Enzyme B did not affect the AME of lupins nor the ileal digestibility of nutrients, but caused an increase in the concentrations of soluble non-starch polysaccharides in the ileal digesta of chickens (19.21-35.77 mg/ml). This was accompanied by an increase in ileal digesta viscosity (11.4-34.2 m.Pa/s).