Modelling the metabolic characteristics of proteins in dairy cattle from co-products of bioethanol processing: comparison of the NRC 2001 model with the DVE/OEB system.

BACKGROUND

Co-products from bioethanol processing include wheat dried distillers grains with solubles (DDGS), corn DDGS, blend DDGS (e.g. wheat/corn at 70:30, 60:40 or 50:50 w/w), triticale DDGS, barley DDGS and pea DDGS. The objective of this study was to compare two systems, the DVE/OEB system versus the NRC 2001 model, in modelling the metabolic characteristics of proteins in dairy cattle from different types of co-products (DDGS) from different bioethanol processing plants.

RESULTS

The predicted values from the NRC 2001 model were 10% higher (P < 0.05) in truly absorbable rumen-synthesised microbial protein in the small intestine, 10% lower (P < 0.05) in truly absorbed rumen-undegraded feed protein in the small intestine, 30% lower (P < 0.05) in endogenous protein and 2% lower (P < 0.05) in total truly absorbed protein in the small intestine than the predicted values from the DVE/OEB system. However, no significant difference was detected in terms of the degraded protein balance between the two models (P > 0.05).

CONCLUSION

The sensitivity of the two models in detecting differences among DDGS types and between bioethanol plants was similar. The two models coincided in the superior protein value of blend DDGS as well as in the more optimal degraded protein balance (DPB) for corn DDGS. Although the differences between the DVE/OEB system and the NRC 2001 model were significant (P < 0.05) for most outputs owing to differences in some of the concepts and factors used in modelling, the correlations between total truly absorbed protein (DVE) and metabolisable protein (MP) values and between degraded protein balances (DPB(OEB) vs DPB(NRC) ) were also significant (P < 0.05).