PSIX-12 Screening of peptides for their impact of protease, protease dose and peptide dose on in vitro rumen dry matter digestibility

The objective of this study was to screening peptides for the effects on in vitro rumen dry matter (DM) digestibility (DMD) of feeds in batch culture. Three brewers spent grain (BSG) samples from different batches were obtained from a local brewery. Peptides were developed with BSG protein varying protease (alcalase, everlase, flavourzyme) and protease dosages (protease:BSG protein; 1:100, 5:100, 10:100, 15:100) under optimum pH and temperature conditions. In total, 36 peptides were produced and screened. A series of batch cultures were conducted and substrates were barley silage and barley grain. The experiment was a complete randomized design with a factorial arrangement; 3 proteases × 4 protease doses + 4 doses of each peptide (0, 0.5, 1.0, 1.5% of substrate DM) with 3 replications of each treatment combination. Rumen inoculum was from three rumen fistulated beef heifers fed a diet consisting of 10% silage and 90% concentrate (DM basis). The incubation was conducted at 39°C for 24 h. Interactions among protease, protease dose and peptide dose were not significant. For barley grain, DMD differed (P < 0.01) among proteases (85.2, 72.3, 65.2%, respectively, for alcalase, flavourzise, everlase). Increasing peptide doses from 0, 0.5, 1.0 to 1.5% linearly (P < 0.01) decreased the DMD from 88 to 78% (alcalase), 69 to 59% (everlase) and 78 to 67% (flavourzyme); whereas protease dose did not affect the DMD. With barley silage, the DMD was higher (P < 0.05) with flavourzyme (65.3%) than alcalase (59.2%) or everlase (61.2%); in contrast, the DMD was affected neither by protease dose nor by the peptide dose, except that increasing supplementation of peptide derived from everlase linearly (P < 0.05) decreased the DMD (65.1 to 58.9%). These results indicated that the peptides derived from BSG decreased in vitro rumen feed digestibility, which varied with proteases, peptide dose or feeds.