Prediction of apparent protein digestibility by in vitro pH-stat degree of protein hydrolysis with species-specific enzymes for Siberian sturgeon (Acipenser baeri, Brandt 1869)

In the present study in vivo apparent protein digestibility (APD) and in vitro degree of protein hydrolysis (DPH; pH-stat assay) of numerous feed ingredients (n = 10) were investigated in juvenile Siberian sturgeon (290 ± 22 g). The ingredients included: fish meal (FM; Clopeonella), meat and bone meal (MBM), poultry by-product meal (PBM), spray dried blood meal (BM), feather meal (FeM), solvent extract soybean meal (SBM), canola meal (CM), corn gluten meal (CGM), wheat gluten meal (WGM), and bakers' yeast (BY). APD values of the ingredients varied from 60 to 92.9% (feather meal and fish meal, respectively). APDs lower than 70% were found in blood meal (68.5%), soybean meal (66.2%), bakers' yeast (66%), canola meal (61%) and feather meal (60%). Also, the ingredients indicated APD values higher than 70%; corn gluten meal (74.3%), wheat gluten meal (76.9%), poultry by-product meal (83.1%) and meat and bone meal (85.6%). Higher DPH values (> 5%) were observed for fish meal, poultry by-product meal and wheat gluten meal; mid-range DPH values (3-5%) for corn gluten meal, meat and bone meal, soy bean meal, blood meal, bakers' yeast; and lower DPH values (<2%) for canola meal and feather meal. Linear regressions between in vivo APD and in vitro degree of DPH with enzyme extracts in feed ingredients for Siberian sturgeon resulted in a considerable correlation (R2 = 0.89-0.99). Also, linear regressions between APD and DPH suggested a close relationship between peptide bond breakage by pyloric caeca and intestine digestive enzymes and the ADP. As a result, this may be a useful tool to provide important nutritional information.