Nutrient variability for distillers grains plus solubles and dry matter determination of ethanol by-products1

Three experiments were conducted to evaluate nutrient content and DM determination methods of dry milling byproducts. In Exp. 1, nutrient composition was determined for wet distillers grains plus solubles (WDGS) and modified distillers grains plus solubles (MDGS) from 6 ethanol plants with 10 samples collected per day, across 5 d, and sampling was repeated over 4 separate months. Mean composition was 31.0% CP, 11.9% fat, 0.84% P, and 0.77% S (DM basis). Coefficients of variation for DM content were greater for some plants than others, and variation occurred within and across days. Variability was small for CP and P, whereas fat differed among ethanol plants. Large variation in means and CV were observed for S in period 1, but variation subsequently decreased. Coefficients of variation for S were similar for samples collected within the same day and across days. In Exp. 2, samples of WDGS, MDGS, Dakota Bran Cake, and distillers solubles were used to determine DM content by drying samples at 105°C for 3, 8, and 24 h and 60°C for 24 and 48 h, vacuum oven drying, toluene distillation, and Karl Fischer titration. Compared with toluene distillation, drying at 105°C resulted in less DM (P ≤ 0.10) and vacuum drying and Karl Fischer titration resulted in greater DM (P < 0.01). In Exp. 3, additional WDGS, MDGS, and wet grains with no solubles were used to determine DM with oven drying at 60°C for 48 h, oven drying at 105°C for 3 h, or toluene distillation. Drying at 60°C for 48 h was similar to toluene distillation (P ≥ 0.60).