Variation in chemical composition of corn dried distillers grains with solubles in relation to in situ protein degradation profiles in the rumen

Abstract

Chemical composition and in situ degradation profiles were analyzed for 27 samples of dried distillers grains with solubles (DDGS) distributed in Japan, and a wide variation was found in neutral detergent fiber (NDF) content, which had positive relationships to detergent-insoluble crude proteins such as neutral detergent-insoluble crude protein (NDICP) and acid detergent-insoluble CP (ADICP). Samples with lower NDF (< 35% on dry matter (DM)) showed higher soluble fractions of protein, but the degradation rate of microbially degradable protein in the rumen was not different in comparison with the samples with higher NDF, and no difference was shown between samples with higher and lower NDF after 24 and 48 h of in situ incubation for DM and CP degradation, respectively. The NDICP content in the digestion residue decreased with time of incubation, especially for samples with higher NDF, while the ADICP content increased. These results suggest that a part of the soluble fraction of CP in DDGS would be incorporated into NDICP by the heating process in bio-ethanol production, which is still highly degradable, whereas another part of the fraction incorporated into ADICP would proceed to the advanced steps of irreversible amino-carbonyl reaction.