Estimation of ruminal and intestinal digestion profiles, hourly effective degradation ratio and potential N to energy synchronization of co-products from bioethanol processing

BACKGROUND: Little research has been conducted to determine the magnitude of the differences in nutritive value among wheat dried distillers' grainswith solubles (DDGS), corn DDGS and blend DDGS, or between different bioethanol plants. The objectives of this study were to compare different types of DDGS and different bioethanol plants in terms of: (1) rumen degradation kinetics profile of each DDGS component and rumen availability; (2) intestinal digestion profile of rumen undegraded protein; (3) hourly effective rumen degradation ratio and potential N-to-energy synchronization; (4) the role of acid detergent insoluble nitrogen in the determination of nutrient availability of DDGS. In addition, these parameters were compared in DDGS as opposed to parental grain. RESULTS: (1) The effective degradability of dry matter in DDGS samples increased as the content of feedstock wheat increased. DDGS are a good source of rumen-undegradable protein. The protein content of DDGS derived from wheat is higher relative to that derived from corn; however, the undegradability of the protein fraction increases as the proportion of corn in the feedstock augments. (2) In addition, DDGS provide significant amounts of rumen-degradable protein, which increased as the content of wheat in the feedstock increased. This indicates a potential loss of N when high levels of DDGS are included in the diet. (3) Acid detergent insoluble crude protein (ADICP) levels were low across DDGS samples, revealing no effect on ruminal and intestinal disappearance of protein. However, consideration should be given to the numerical differences in digestibility of rumen-undegradable protein and the relation to ADICP content. (4) Further research with a higher number of samples and higher variability in the ADICP content should be undertaken to investigate the effect of ADICP on rumen and intestinal disappearance of DDGS protein. CONCLUSION: The digestive characteristics of each DDGS component (dry matter, organic matter, crude protein and neutral detergent fiber), the hourly effective degradation ratio between N and organic matter, and the intestinal availability of rumen-undegradable protein differed significantly (P < 0.05) among wheat DDGS, blend DDGS and corn DDGS, and to a lesser extent between the different bioethanol plants. These results indicate that it is inappropriate to assume fixed rumen and intestinal degradation characteristics for DDGS without considering factors such as DDGS type and bioethanol plant origin. © 2010 Society of Chemical Industry.