Distillers Dried Grains with Solubles: Determination of Metabolizable Energy Values Using Regression-Based Assays and their Correlation with Chemical Composition

The inherent variability and lack of standardization of in vivo assays to determine the metabolizable energy (ME) of DDGS has led to inconsistent values and limited its potential to use in broiler diets. Therefore, two experiments were conducted to characterize the content of nitrogen-corrected ME (MEn) in 11 DDGS sources obtained from various ethanol plants using a regression-based broiler assay and to attempt to develop equations to predict MEn based on its chemical composition. In experiment 1, the objectives were to determine the influence of inclusion level and feed intake on the resulting ME and MEn values of a single DDGS source when fed to broilers at multiple dietary inclusion levels. The ME and MEn values of DDGS determined by difference decreased as its dietary concentration increased. Pair-feeding the 30% DDGS diet to the 60% DDGS diet intake reduced the ME and MEn values of DDGS, indicating there was an effect of feed intake on the ME value of DDGS. Additionally, the MEn of DDGS was determined by two regression-based methods. First, the DDGS associated caloric intake was regressed against the amount of DDGS intake to generate linear regression equations with slopes corresponding to the MEn value of DDGS. Secondly, the dietary MEn was regressed against the DDGS inclusion level, and extrapolation of the regression line to 100% DDGS was used to estimate its ME value. Both regression methods yielded similar ME and MEn values of DDGS. Experiment 2 determined the MEn of 11 DDGS samples obtained from different biorefinery locations operated by a single ethanol producer and related these values with chemical composition and physical properties of the DDGS samples. Analyses of DDGS included gross energy, CP, Lys to CP ratio (Lys:CP), ether extract, DM, starch, total dietary fiber (TDF), neutral detergent fiber (NDF), acid detergent fiber (ADF), color scores, and particle size. On a DM basis, MEn of the 11 DDGS sources ranged from 2,284 to 3,088 kcal/kg with a CV of 7%. Hemicellulose was the only component found to be correlated with the MEn of DDGS. As a result, the lack of correlations between DDGS composition and its MEn precluded development of prediction equations. Overall, these results indicate that the MEn of DDGS estimated in MEn assays is influenced by its inclusion level in the test diet and partly due to effects on feed intake While the narrow variability in the chemical composition of the DDGS sources did not allow for the development of prediction equations, these results provide good insight into the energy utilization and uniformity of these sources for poultry feed formulations