Chemical characterization and in situ nutrient degradability of wet distillers’ grains derived from barley-based ethanol production

A study was conducted to characterize the carbohydrate and protein fractions of barley-based distillers grains (BDG) derived from a mix of 70% barley, 20% wheat and 10% rye/triticale. Amino acid composition, ruminal escape protein and amino acid values, and ruminal nutrient degradability of BDG were determined relative to wheat-based distillers’ grains (WDG) derived from 100% wheat. On a dry matter (DM) basis, BDG contained 743 g kg−1 neutral (NDF) and 311 g kg−1 acid (ADF) detergent fibre, and 154 g kg−1 crude protein (CP). More than 50% of BDG protein was associated with NDF while 17% was associated with ADF. Glutamic acid was the most abundant amino acid in both distillers grains and was lower (p < 0.05) in BDG (184 g kg−1 of amino acids) than WDG (243 g kg−1 of amino acids). The concentration of lysine was higher (p < 0.05) in BDG than in WDG while that of methionine was similar in both byproducts. Ruminal escape protein value was greater (p < 0.05) for BDG than for WDG. However, the ruminal escape values for most of the amino acids were not different between BDG and WDG. Ruminal degradability of NDF from WDG (454 g kg−1 of NDF) was higher (p < 0.05) than that from BDG (360 g kg−1 NDF). The results of this study showed that fibre and protein fractions of BDG are less degradable in the ruminal than the corresponding fraction from WDG. However, data of amino acid composition and ruminal undegradability suggest that the quality of amino acids of BDG reaching the small intestine of ruminants is equal or better than that from WDG.