Dry matter of the test ingredients, experimental diets and faeces as well the crude protein, crude lipid and ash of the ingredients and diets were determined following the procedures of the Association of Official Analytical Chemists (AOAC, 2005). Dry matter was determined after oven drying for 24 h at 105 °C (Memmert UN110). Ash contents were calculated from the weight loss after incineration of the samples for 6 h at 550 °C in a muffle furnace (Hareaus Instruments K1252). Crude protein levels were determined from the Kjeldahl method (Foss Kjeltec 2200) and crude lipid by the method of Bligh and Dyer (1959).