Effect of bioethanol co-product type on ruminal degradation and amino acid intestinal digestibility

The objectives of this experiment were to measure the nutrient content of distiller grains (DG) with solubles (DDGS) produced from maize (4 samples of DDGSM), wheat (4 samples of DDGSW), triticale (DDGST) and wet distillers grains (2 samples of WDG) from maize. The ruminal CP degradability and bypass CP and amino acid (AA) intestinal digestibility were determined using in sacco and mobile bag technique on three dry cows with ruminal cannulae and permanent T –canulae in the duodenum. Samples of DG were incubated in the rumen for 3, 6, 9, 16, 24, 48 and 96 h. Intestinal CP and AA digestibility were measured on residue from 16 h ruminal incubation of DG. There were significant differences among DG in crude protein (CP), neutral detergent fibre (NDF), nitrogen insoluble in neutral detergent solution (N-NDF) and nitrogen insoluble in acidic detergent solution (N-ADF). The highest proportion of N bound to NDF and ADF was recorded in DDGSW (26.3% and 28.3%) and DDGST (21.2% and 26.1%). The ruminally degradable CP fraction was variable in the range from 48.2 to 71.0% for DDGSW, 52.6 to 70.0% for DDGSM and 69.4% for WDG, respectively. The content of amino acids was higher in DG from maize than in DG from wheat or triticale. Large differences were observed among the samples in the content of leucine, lysine, histidine and methionine. The lowest content of lysine and essential AA (EAA) was recorded in DDGS from wheat. The large variation in the content of lysine (from 4.6 to 9.5 g per kg DM), leucine (from 21.8 to 57.0 g per kg DM) and methionine (from 5.1 to 9.2 g per kg DM) in bypass CP was observed among samples of DG. Intestinal digestibility of bypass protein and EAA was greater in DDGS from maize ( 95% and 96%, resp.) than in DDGS from wheat (79-91% and 81-93%, resp.) and triticale (89% and 91%, resp.). The lowest and variable intestinal digestibility was determined for lysine (from 77.6 to 91.5% and histidine (from 77.6 to 95.6%) in all tested samples of DG. Protein degradability and digestibility differed greatly among DG sources. This phenomenon needs additional study.