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The growing ethanol industry has produced vast quantities of distillers grains plus solubles (DGS) in the wet (WDGS) and dry forms and Sweet Bran wet corn gluten feed (SB). Previous research has demonstrated that these byproduct feeds result in improved feeding values compared to grass in growing diets and corn in finishing diets, with positive economic returns. Four experiments were conducted to evaluate dry matter determination methods and variability of nutrient composition for WDGS, determining the accurate method for measuring NDF in corn and DGS, compare feeding WDGS mixed with straw as either fresh or ensiled, and evaluate fiber digestibility and metabolism characteristics for feeding WDGS and SB in finishing diets. Drying wet byproduct feeds at 60ºC for 48 h was similar to toluene distillation, but these were different compared to drying at 105ºC for 3, 8, or 24 h, vacuum oven drying, and Karl Fischer titration. Mean composition of WDGS was 31.0% CP, 11.9% fat, 0.84% P, and 0.77% S (DM basis). Variation of CP and P was small. Dry matter and fat varied more across ethanol plants than within and across days. Variation in S was greater in period 1, but decreased in subsequent periods and variation was similar within days compared to across days. Grinding corn samples through a 1-mm screen Tecator Cyclomill and using two doses of alpha-amylase during the relux process results in the most accurate NDF values. Using a pre-fat extraction step prior to the traditional NDF procedure results in more accurate NDF values for DGS. Increasing the level of WDGS from 30 to 45% DM and mixing this with straw resulted in increased ADG and G:F and feeding these mixtures as ensiled also resulted in improved ADG and G:F compared to feeding them as fresh mixes. Steers fed SB at 35 or 88% DM consumed more DM and NDF compared to feeding 35% WDGS. Feeding a Lactobacillus buchneri direct-fed microbial did not affect DM or NDF digestibility for feeding diets containing 35% SB or WDGS, but did increase digestibility for feeding 88% SB. Monitoring accurate DM and nutrient composition of DGS, and accurately determining NDF content of corn and DGS makes for useful information in evaluating fiber utilization of byproduct feeds in growing and finishing diets. Feeding WDGS stored with straw results in greater cattle performance compared to the fresh mix and using the DFM in 88% SB diets improves digestibility.