Energy value of wheat, barley, and wheat dried distillers grains with solubles for broiler chickens determined using the regression method

The energy value of wheat, barley, and 2 samples of wheat dried distillers grains with solubles (WDDGS) for broiler chickens were determined in 2 experiments with Ross 708 broiler chickens from d 15 to 22 posthatch. The birds were fed a standard broiler starter diet from d 1 to 15 posthatch. In each experiment, 320 birds were grouped by weight into 8 blocks of 5 cages with 8 birds per cage and assigned to 5 diets. There were 5 diets in each experiment consisting of a corn-soybean meal reference diet (RD) and 4 test diets (TD). The TD consisted of each of the 2 WDDGS samples (experiment 1), wheat, or barley (experiment 2) that partly replaced the energy sources in the RD at 100 or 200 g/kg such that the same ratios were maintained for all energy ingredients across all experimental diets. The ileal digestible energy (IDE), ME, and ME of the WDDGS samples, wheat, and barley were determined by the regression method. Dry matter of WDDGS1, WDDGS2, wheat, and barley were 939, 947, 899, and 890 g/kg, respectively; the gross energies were 4,838; 4,825; 4,456; and 4,567 kcal/kg of DM, respectively. Addition of WDDGS to the RD in experiment 1 linearly decreased (P < 0.01) ileal nitrogen and energy digestibilities, total tract utilization of DM, energy and nitrogen, as well as ME and MEn of the TD. In experiment 2, IDE, ME, and MEn in the TD decreased (P < 0.01) with increasing levels of barley in the diets, but wheat inclusion had no effect on the IDE, ME, and ME, of the diets. Wheat inclusion linearly improved (P < 0.05) DM and energy utilization in TD. The DE, MEn, and MEn of the test ingredients were determined by the regression method in which the test ingredient contribution to DE, ME, and MEn in kilocalories was regressed against the amount of test ingredient in grams. The IDE were 2,001 and 1,831 kcal/kg of DM for WDDGS1 and WDDGS2, respectively. The respective ME and MEn values were 2,644 and 2,464 kcal/kg of DM for WDDGS1 and 2,215 and 2,092 kcal/kg of DM for WDDGS2. The respective IDE, ME, and MEn of wheat for broiler chickens were 3,413; 3,713; and 3,372 kcal/kg of DM. The barley sample evaluated contained 2,364 kcal of IDE, 2,894 kcal of ME, and 2,841 kcal of MEn/kg of DM for broiler chickens.