Brewers' Spent Grain Residues After Extraction With Proteases Of Different Concentrations Showed Digestibility Differences In Batch Culture

Brewers’ spent grain (BSG) has been used as animals feed for many years. Recent experiments isolated proteins and biologically active peptides from BSG. Although, the residue after extraction is a potential feed source to animals, no data is available on the digestibility. The objective was to evaluate the effects of enzyme and enzyme concentration used for peptide extraction on gas production (GP) and DM digestibility (DMD) of residue in batch culture. The study was a 3 × 4 + 1 factorial arrangement including enzyme (alcalase, everlase, flavourzyme) and enzyme concentrations (1, 5, 10, 15%) plus original BSG. Residue (0.50 g) was incubated for 24 h in culture bottle in three replications. The culture was repeated at different day. Data were analysed using MIXED procedure of SAS with fixed effects of enzyme, enzyme concentration and interaction, and random effects of day. Type of enzyme and concentration showed interactions (P<0.01) with GP and DMD. Volume of GP (ml/g DM) and rate of GP (%/h) linearly (P<0.01) decreased, respectively, from 102 to 85 and from 4.9 to 3.9 with increasing alcalase concentration. Magnitudes of the differences in GP and rate of GP among 3 enzymes varied with enzyme concentration applied during peptide extraction. The DMD of residues was highest (P<0.05) with alcalase (44.5%), intermediate with everlase (41.4%) and lowest with flavourzyme (35.8%) at 1%, similar DMD at 5%, and greater (P<0.05) DMD with everlase than alcalase and flavourzyme at 10% or 15% enzyme concentration. The DMD of residues linearly (P<0.01) decreased with increasing alcalase concentration but linearly (P<0.02) increased with increasing flavourzyme concentration. Additionally, the DMD of residues (averaged 40.4%) was lower (P<0.01) than that of BSG (45.6%). These results indicated that the protease-based peptide extraction decreased ruminal BSG digestibility and magnitude of the digestibility reduction varied with type and concentration of protease used during peptide extraction.