Nutrients apparent digestibility coefficients of selected protein sources for juvenile Siberian sturgeon (Acipenser baerii Brandt), compared by two chromic oxide analyses methods

Apparent digestibility coefficients (ADCs) of dry matter (ADC(d)), crude protein (ADC(p)), energy (ADC(e)) and amino acids in selected feedstuffs were determined for juvenile Siberian sturgeon (8.38 +/- 0.20 g). The tested feedstuffs were fishmeal (FM), meat and bone meal (MBM), poultry by-product meal, hydrolysed feather meal, fermented feather meal solvent-extracted cottonseed meal and soybean meal. ADCs were determined using a reference diet and test diets at 7 : 3 ratios with 5 g kg-1 chromic oxide (Cr2O3) as an inert marker. Fish were reared in a recirculating system and fed to apparent satiation five times daily. Cr2O3 in diets and faeces samples were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) and acid-digestion colorimetry (AC) methods, respectively. The results showed that ICP-AES method was more accurate for Cr2O3 determination than AC method, and the results determined by ICP-AES method were used in this study. ADC(d) and ADC(p) of seven tested ingredients were lowest for MBM (59.1 and 84.5%) and highest for FM (79.9 and 94.5%); ADC(e) of tested ingredients were from 71.8% for SECM to 93.2% for FM. ADCs of amino acid in test ingredients followed similar trend to the ADC(p). The ADCs of individual amino acids varied from 61.6% (histidine in MBM) to 98.8% (valine in FM).