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Energy value of de-oiled wet distillers grains plus solubles relative to corn processing method of steam-flaked or dry-rolled
As ethanol plants have begun removing oil from thin stillage during the ethanol production process, fat content of distillers grains has decreased. The objective of this study was to evaluate the energy value of de-oiled wet distillers grains plus solubles (WDGS) when fed with either dry-rolled corn (DRC) or steam-flaked corn (SFC). A 128-d finishing trial was conducted utilizing 320 yearling steers (initial BW = 397 ± 38kg) with 8 treatments (5 pens/treatment). Data were analyzed as 2 separate factorials. The first factorial was a 2×3 with factors of de-oiled WDGS in the diet at 0, 17.5, or 35% (DM basis) fed with DRC or SFC. The other was a 2×2 factorial by using two additional diets containing 35% normal WDGS with either DRC or SFC compared to 35% de-oiled WDGS fed with both corns. Normal and de-oiled WDGS were received from two different plants for this study. Steers were blocked by BW, stratified within block, and pens were assigned randomly to treatments within block. No WDGS concentration by corn processing method interaction existed when evaluating the 2×3 factorial (G:F, P = 0.15). Steers fed DRC had greater DMI compared to steers fed SFC (P = 0.02), similar ADG (P = 0.23); however, G:F was improved in steers fed SFC (P = 0.01). Increasing the concentration of WDGS in the diet linearly increased final BW, ADG, G:F, HCW and fat depth (P < 0.01). Increasing the concentration of WDGS from 0 to 17.5% caused a 5.0% improvement in G:F and increasing from 17.5 to 35% caused a 3.4% improvement in G:F. Marbling scores increased quadratically (P = 0.01) with increasing concentrations of WDGS. When comparing 35% de-oiled WDGS to 35% normal WDGS, there were no corn processing method by WDGS type interactions (P ≥ 0.29). Type of WDGS did not significantly impact G:F (P = 0.14) but normal was 2.4% numerically greater in DRC diets and 5.2% numerically greater in SFC-based diets. Steers fed SFC had greater G:F (P = 0.05) than those fed DRC as expected. This study suggests that increasing the concentration of de-oiled WDGS in the diet while feeding either SFC or DRC improves G:F. Removing a portion of the oil did not significantly impact G:F but feeding normal WDGS numerically improved G:F suggesting oil removal may have a small effect on energy value.
Keywords: corn processing, distillers grains plus solubles, oil removal