STRATEGIES TO IMPROVE THE NUTRITIVE-VALUE OF RICE BRAN IN POULTRY DIETS - II - CHANGES IN OIL DIGESTIBILITY, METABOLIZABLE ENERGY AND ATTEMPTS TO INCREASE THE DIGESTIBILITY OF THE OIL FRACTION IN THE DIETS OF CHICKENS AND DUCKLINGS

1. In experiment 1, the effects of age on oil digestibility and appare nt metabolisable energy (AME) were measured in chickens and ducklings between 3 and 28 d of age on a diet with 400 g rice bran/kg. In experi ment 2, a biosurfactant and a food lipase were added to diets of chick ens containing 200 and 400 g rice bran/kg. In experiment 3; chicken di ets containing 0 or 400 g rice bran/kg were supplemented with a food l ipase (2 concentrations) or a food enzyme or their combination. 2. In experiment 1, oil metabolisability and AME increased substantially as chickens aged. Oil metabolisability was much higher in ducklings, when comparisons were made with chickens of similar age. 3. In experiment 2, lipase or biosurfactant gave no improvement in bird performance. Gr owth rate and food conversion ratio were, respectively, 23% and 10% be tter on diets with 200 compared to 400 g rice bran/kg. 4. In experimen t 3, there was a significant growth response to lipase plus the enzyme mixture on the diet with 200 g rice bran/kg. On the diet with 400 g r ice bran/kg, growth improvement was seen with the enzyme mixture only. 5. In experiment 3, enzyme addition did not increase oil metabolisabi lity or AME. At 4 to 28 d of age AME was higher on the diet without ri ce bran but oil metabolisability was the same as on the diet with rice bran. At 19 to 23 d of age AME was similar hut oil metabolisability w as higher on the diet with rice bran than without. Droppings' dry matt er was higher on diets without than with rice bran (32.4 vs 27.1%). 6. The response to lipase and the combination of this and a food enzyme suggest that there may be benefit in examining this interaction furthe r although they had no effect on oil metabolisability or on AME. It is concluded that a stable AME for rice bran cannot be provided for chic kens until at least 21 d of age.