Apparent crude protein (ADCCP), crude fat (ADCCF) and gross energy (ADCGE) digestibility coefficients of several typical and novel feedstuffs were determined to be employed in the formulated diets of subadult beluga (17.70 ± 0.234 kg) diets via two faecal collection methods of settlement (SFCM) and stripping (StM). The tested feedstuffs included three fish meals, three terrestrial animal by-products, three plant protein concentrates, nine high-protein plant meals and three low plant protein meals. ADCCP values varied in different fish meals ranging from 89.5% for Mexican sardine meal to 93.2% for anchovy meal with SFCM. ADCCP values for plant protein concentrates ranged from 82.8% for wheat gluten meal to 92% for soy protein with SFCM. ADCCP ranged from 37.2% for whole wheat to 75.6% for spirulina meal with SFCM. ADCGE was lower in low-protein plant meals (64.1%) in comparison to high-protein plant meals (70.2%). Fish meals showed the highest ADCCF values. A significant (P < 0.05) quadratic regression relation (r2 = 0.92) was observed among in vivo ADCCP of five feedstuff classes fed to beluga and in vitro ADCCP. The differences among ADC values appear to be significantly related to the effects of feedstuffs and therefore diet and faecal collection methods.