Contribution of exogenous dietary carbohydrases to the metabolizable energy value of corn distillers grains for broiler chickens

The objectives of this study were to determine the ileal digestible energy (IDE), ME, and MEn contents of corn distillers grains (CDG) for broiler chickens and to quantify these energy utilization responses to carbohydrase supplementation by the regression method. The CDG sample used in the current experiment contained (by analysis) 936 g/kg of DM, 4,894 kcal/kg of gross energy, 315.1 g/kg of CP, 94.6 g/kg of crude fat, 94.8 g/kg of crude fiber, 495.6 g/kg of neutral detergent fiber, 179.1 g/kg of acid detergent fiber, 0.19 g/kg of Ca, and 4.8 g/kg of P. The studies were conducted at 2 locations (Purdue or Louisiana State University) and CDG were incorporated into a practical corn-soybean meal diet at 3 levels (0, 300, or 600 g/kg) without or with added carbohydrase in a 2 x 3 x 2 factorial arrangement. The carbohydrase premix was added to supply 2,000 U of xylanase + 1,800 U of amylase/kg of feed. The diets were fed to 288 broiler chickens from d 15 to 22 posthatch with 6 birds per cage and 8 replicate cages per diet in a randomized complete block design at each of 2 locations. The broiler chicks were fed a standard broiler starter diet from d 1 to 15 posthatch. The IDE of diets decreased both linearly (P < 0.01) and quadratically (P < 0.05) as CDG increased from 0 to 600 g/kg regardless of carbohydrase supplementation. There was a linear (P < 0.01) decrease in ME of diet from 3,239 to 2,510 kcal/kg as CDG increased from 0 to 600 g/kg in the diets without added carbohydrase, whereas for birds fed the carbohydrase-supplemented diets, there were both linear (P < 0.01) and quadratic (P < 0.01) decreases from 3,398 to 2,613 kcal/kg as CDG increased from 0 to 600 g/kg. Dietary MEn linearly decreased (P < 0.01) regardless of carbohydrase supplementation as CDG increased from 0 to 600 g/kg. Supplementation with carbohydrase improved (P < 0.01) IDE, ME, and MEn. Regressions of CDG-associated IDE, ME, or MEn intake in kilocalories against kilograms of CDG intake without added carbohydrase generated the following: IDE = 44 + 2,340X, r² = 0.953; ME = 10 + 2,315X, r² = 0.993; and MEn = 10 + 2,132X, r² = 0.991. Corresponding regressions when carbohydrase was added were as follows: IDE = -17 + 2,622X, r² = 0.985; ME = -25 + 2,448X, r² = 0.979; and MEn = -22 + 2,264X, r² = 0.978. These data indicate that the respective IDE, ME, and MEn values (kcal/kg of DM) of the CDG sample evaluated were 2,340, 2,315, and 2,132 when carbohydrase was not added and 2,622, 2,448, and 2,264 when carbohydrase was added. Comparison using ANOVA procedures indicated that the slope when carbohydrase was added was greater (P < 0.05) than when carbohydrase was not added. This response implies that carbohydrase supplementation improved (P < 0.05) the IDE, ME, and MEn of CDG in practical corn-soybean meal-based diets used in this current study by 12, 5.7, and 6.2%, respectively.