Nutrient content of brewers grains produced at a commercial brewery: Variation in protein/nitrogen, fiber, carbohydrate, fat, and minerals

This study analyzed wet brewers grain samples taken from a large commercial brewery. Samples (n = 48) taken over a 1-yr period averaged 33.1% CP (previous reports indicated CP% near or less than 30%). Low lysine concentrations and high RUP concentrations indicate a need for proper RUP and amino acid (AA) formulation. Samples were also divided and composited into low- and high-CP groups; every 3 samples, starting from the least to the greatest CP, were composited to produce 16 samples representative of the range in CP. These samples were analyzed for DM, CP, ammonia N, and AA concentration. The 8 lowest CP composites averaged 32.2% CP and the 8 highest averaged 34.0% CP. A difference was observed in AA concentrations (analyzed from borate-phosphate buffer residues, which contain insoluble true protein and are useful in determining RUP) between the 2 groups (P < 0.05), but AA profiles were consistent between the 2 CP composite groups. Fiber (NDF) fractions were analyzed both with and without added sulfite. This yielded different results between methods, as samples without added sulfite yielded NDF values greater than current published values; hence, the use of sulfite is recommended for NDF analysis. Fat, starch, sugar, and mineral concentrations were within ranges already published.