In vitro digestibility and nutritional characterization of distillers dried grains with solubles according to the Cornell Net Carbohydrate and Protein System

Abstract

We evaluated the fractions of protein and carbohydrates in distillers dried grains with solubles (DDGS), corn grain (CG), soybean meal (SM), and corn silage (CS), as well as the in vitro digestibility (IVD) of DDGS, CG, SM, CS, rations containing 0.0, 8.0, 16.0, and 24.0% DDGS, and in vitro fermentation parameters after 24 h of incubation. DDGS were obtained following microbial fermentation for ethanol production from a sugar and alcohol distillery located in the state of Mato Grosso - Brazil. The Cornell Net Carbohydrate and Protein System (CNCPS) was used to determine the protein and carbohydrate fractions of experimental diets. For the in vitro nutrient digestion assay using the experimental foods and experimental diets, two sheep with an average body weight of 26 kg were used as inoculum donors. The in vitro digestibility of food and feed was assayed in three replicates. Fraction A of DDGS CP was 88, 71, and 37% lower in relation to fraction A of SM, CG, and CS, respectively. Fraction B2 of DDGS protein contained 21% CP, which represents 78.84% of DDGS protein in fraction B2, and is higher than the SM, which was 70.44%. The B3 fraction of CP, which is partly released during ruminal fermentation, was 18% lower for SM compared to DDGS, and is expressed in %CP. For carbohydrate fractionation, the DDGS presented 8.64% for the A + B1 fraction on a DM basis, which was 62, 86, and 74% lower compared to those obtained for SM, CG. and CS, respectively. The hemicellulose and cellulose contents of DDGS were higher than those of SM, as verified in fraction B2, with a value of 46.92%, expressed in DM. The in vitro digestibility coefficients (IVDC) of the DDGS nutrients did not differ (p > 0.05) in relation to those of the other experimental foods. The inclusion of DDGS in rations formulated for sheep did not change (p > 0.05) the IVDC of DM, OM, CP. NDF, or ADF, with mean values of 70.93, 70.64, 59.58, 52.83, and 43.40%, respectively. Therefore, DDGS comprise a protein-rich food containing more than 70% CP in fraction B2, with a large amount of carbohydrates bound to the cell wall. In addition, DDGS possess a similar digestibility coefficient to corn grain and soybean meal; however, up to 24% can be included in feed formulations for ruminants without changing the in vitro digestibility coefficient of nutrients.