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Digestibility of traditional and Adding Cellulosic Ethanol wet distillers grains in finishing lambs
The feeding value of further processed distillers grains is unclear. A new, secondary fermentation process for converting corn kernel fiber into cellulosic ethanol, including a pretreatment with cellulosic enzymes, yeast, and heat, results in a novel wet distillers grain (WDG) called Adding Cellulosic Ethanol WDG (A-WDG). The study objective was to evaluate the impact of increasing inclusion of WDG from traditional WDG (T-WDG) or A-WDG on nutrient digestibility in lambs. Ten wethers (34.1 ± 0.74 kg) were used in a replicated 5 X 5 Latin square with 15-d periods, including10-d of diet adaptation and 5-d of fecal and urine collection. Lambs received 1 of 5 diets per period: a corn-based control containing 7.5% each of T-WDG and A-WDG (CON), and 30% and 45% inclusion of T-WDG (30T-WDG or 45T-WDG) or A-WDG (30A-WDG or 45A-WDG) on a DM basis. Data were analyzed using PROC MIXED. Dry matter intake (DMI) was not affected (P ≥ 0.25) by concentration of T-WDG. However, DMI was quadratically affected (P = 0.02) by increased concentration of A-WDG, due to lesser DMI by lambs fed 30A-WDG. Digestibility of DM tended to decrease quadratically (P = 0.09) in lambs fed T-WDG diets (80.6, 80.0, and 77.4%, SEM 0.57 for CON, 30 and 45T-WDG, respectively). Digestibility of DM linearly decreased (P < 0.01) as A-WDG inclusion in the diet increased (78.3 and 75.3%, for 30 and 45A-WDG, respectively). Diet NDF concentration linearly increased (P < 0.01) with increasing inclusions of A-WDG (24.6, 31.0, and 33.6%, SEM 0.83 for CON, 30A-WDG, and 45A-WDG, respectively). Diet NDF concentration quadratically increased (P = 0.03) with increasing inclusions of T-WDG (26.9 and 32.2%, for 30T-WDG, 45T-WDG, respectively). Digestibility of NDF and ADF did not differ (P ≥ 0.25) with increased inclusion of A-WDG in the diet. A linear increase in NDF and ADF digestibility was observed with increased inclusion of T-WDG (P < 0.05; 50.8, 51.8, and 55.1%, SEM 1.04 for NDF digestibility, and 50.2, 51.8, and 57.2%, SEM 1.74 for ADF digestibility of CON, 30T-WDG, and 45T-WDG, respectively). In this study, WDG from a novel, secondary fermentation process appeared to be an effective substitute for corn in finishing diets, with similar fiber digestibility and a slight decrease in DM digestibility as inclusions increased. With traditional WDG, fiber digestion was linearly improved with increasing inclusions and DM digestibility was decreased only at the highest inclusion.
Keywords: cellulosic ethanol, digestibility, wet distillers grains