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

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1 Energy value of wheat, barley, and wheat dried distillers grains with solubles for broiler chickens determined using the regression method O. A. Bolarinwa1 and O. Adeola2 Department of Animal Sciences, Purdue University, West Lafayette, IN ABSTRACT 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 n 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 INTRODUCTION Efficient production of high quality animal products is mostly dependent on the supply of nutritionally adequate feedstuff to the animal in the right amount and also understanding the digestion characteristics and utilization of such feedstuff. Dietary provision of adequate energy is important for efficient production, and this adequacy is partly dependent on knowledge of the utilizable energy of feed ingredients formulated into diets. Wheat and barley are important energy feedstuffs for poultry diets. Distillers dried grains with solubles (DDGS) is a co-product from the distillation of cereal linearly decreased (P < 0.01) ileal nitrogen and energy digestibilities, total tract utilization of DM, energy and nitrogen, as well as ME and ME n of the TD. In experiment 2, IDE, ME, and ME n 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 n of the diets. Wheat inclusion linearly improved (P < 0.05) DM and energy utilization in TD. The DE, ME, and ME n of the test ingredients were determined by the regression method in which the test ingredient contribution to DE, ME, and ME n 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 ME n 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 ME n 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 ME n /kg of DM for broiler chickens. Key words: barley, dried distillers grains with solubles, metabolizable energy, regression method, wheat 2012 Poultry Science 91 : Poultry Science Association Inc. Received February 28, Accepted April 27, Deceased. 2 Corresponding author: ladeola@purdue.edu grains for alcohol production and is available for inclusion in diets fed to nonruminant animals. During the fermentation process, most of the starch in the grain is converted to alcohol, which leaves a co-product that is highly concentrated in all other nutrients, except starch, that are present in the wheat grain. Therefore, wheat DDGS (WDDGS) contains almost 3 times the concentration of the nutrients in wheat. Several studies have reported the energy value of DDGS from corn for broiler chickens (Lumpkins et al., 2004; Fastinger et al., 2006; Adeola and Ileleji, 2009). Recently, the ME of corn distillers dried grains was reported to be 2,315 kcal/kg of DM and was enhanced by 6% with added carbohydrase (Adeola et al., 2010). A follow-up study reported by Adeola and Zhai (2012) showed that the ME of corn distillers dried grains for birds is lower than that of corn DDGS (2,280 vs. 2,800 kcal/kg of DM). Cozannet et al. (2010) recently reported the ME values 1928

2 of 10 samples of WDDGS for poultry. However, there is limited data on energy value of WDDGS for broiler chickens. Due to the potential of using WDDGS in broiler chicken diets, more data on the ileal digestible energy (IDE), ME, and ME n are needed. Therefore, the objective of the current study was to determine the IDE, ME, and ME n of 2 samples of WDDGS, wheat, and barley for broiler chickens using the regression method. MATERIALS AND METHODS Birds and Management ENERGY VALUES USING REGRESSION METHOD Birds were reared in electrically heated battery brooders maintained at 35 C, 31 C, and 27 C from d 1 to 8, d 8 to 15, and d 15 to 22 posthatch, respectively, with continuous fluorescent lighting. Three hundred sixty (experiment 1) or 340 (experiment 2) 1-dold male Ross 708 broiler chickens were tagged with identification numbers and provided ad libitum access to water and a common starter feed (Table 1) from d 1 to 15 posthatch. The average d 1 posthatch BW, d 15 posthatch BW, and 14-d feed intake were 45, 328, and 490 g, respectively, for experiment 1; corresponding numbers for experiment 2 were 46, 335, and 485 g. On d 15, 320 birds were blocked by weight for each of experiments 1 and 2. The birds were assigned to diets in such a way that the average initial BW (328 or 335 g) was not different across diets. There were 5 dietary treatments, each of which was replicated 8 times with 8 birds per replicate cage for each of experiments 1 and 2. Individual BW of birds and feeder weight per cage were recorded on d 15 and 22 posthatch. Excreta was collected twice daily from d 18 to 20. During collection, waxed paper was placed under the cages and excreta on the waxed paper were collected. The collected excreta samples were pooled per cage over the 2-d period and Table 1. Ingredient composition of starter diets fed from d 1 to 15 posthatch and experimental diets (reference and test diets) fed from d 15 to 22 posthatch in experiments 1 and 2 Item d 1 to 15 Reference diet (RD) d 15 to 22 Test diets (TD) 0 g/kg 100 g/kg 200 g/kg Ingredient, g/kg Corn Soybean meal Soybean oil Monocalcium phosphate Limestone (38% Ca) Salt Vitamin-mineral premix dl-methionine l-lysine, HCl l-threonine 1.1 Corn starch-chromic oxide premix Corn starch Test ingredient Total 1,000 1,000 1,000 1,000 Calculated nutrient content CP, g/kg ME, kcal/kg 3,208 3,126 Ca, g/kg P, g/kg Nonphytate P, g/kg Total amino acids, g/kg Arg His Ile Leu Lys Met Met + Cys Phe Phe + Tyr Thr Trp Val % Ca, 21% P. 2 Supplied the following per kilogram of diet: vitamin A, 5,484 IU; vitamin D 3, 2,643 IU; vitamin E, 11 IU; menadione sodium bisulfate, 4.38 mg; riboflavin, 5.49 mg; d-pantothenic acid, 11 mg; niacin, 44.1 mg; choline chloride, 771 mg; vitamin B 12, 13.2 μg; biotin, 55.2 μg; thiamine mononitrate, 2.2 mg; folic acid, 990 μg; pyridoxine hydrochloride, 3.3 mg; I, 1.11 mg; Mn, mg; Cu, 4.44 mg; Fe, 44.1 mg; Zn, 44.1 mg; Se, 300 μg. 3 Prepared as 1 g of chromic oxide added to 4 g of cornstarch. 1929

3 1930 Bolarinwa and Adeola Table 2. Chemical composition of the test ingredients evaluated in experiments 1 and 2 on an as-is basis 1 Item, g/kg WDDGS1 WDDGS2 Barley Wheat DM Gross energy, kcal/kg 4,181 4,327 4,066 4,006 Nitrogen Crude fat Crude fiber ADF NDF Calcium Phosphorus Indispensable amino acids Arg His Ile Leu Lys Met Phe Thr Trp Val Dispensable amino acids Ala Asp Cys Glu Gly Pro Tyr Ser WDDGS1 = wheat distillers dried grains with soluble 1; WDDGS2 = wheat distillers dried grains with soluble 2. 2 ADF = acid detergent fiber; NDF = neutral detergent fiber. stored in a freezer at 20 C until further processed. Excreta were dried in a forced air oven at 55 C and ground to pass through a 0.5-mm screen in a grinder (Retsch ZM 100, GmbH & Co. K. C., Haan, Germany). On d 22 posthatch, feeders and birds were weighed to determine BW gain and feed intake, and birds were euthanized by CO 2 asphyxiation. Ileal digesta was collected from the Meckel s diverticulum to approximately 2 cm cranial to the ileocecal junction. Ileal contents from birds were flushed with distilled water into plastic containers, pooled by cage, and stored in a freezer 20 C until freeze-dried and ground. All protocols used in the study were approved by the Purdue University Animal Care and Use Committee. Test Ingredients and Diets The test ingredients evaluated for their energy values were 2 samples of WDDGS, wheat, and barley. The analyzed gross energy and chemical composition of the WDDGS, wheat, and barley are presented in Table 2. Dietary treatments consisted of a corn-soybean meal reference diet (RD) and 4 test diets (TD). In the RD (Table 1), corn, soybean meal, corn starch, and soy oil were used as the sources of energy. In the TD used in experiment 1, each of the 2 WDDGS samples were added at 100 or 200 g/kg of diet to partly replace corn, soybean meal, corn starch, and soy oil in such a way as to maintain the same ratio of corn, soybean meal, corn starch, and soy oil across the experimental diets. These ratios were 1.31, 17.68, 12.55, 13.45, 9.55, and 0.71:1 for corn:soybean meal, corn:corn starch, corn:soy oil, soybean meal:corn starch, soybean meal:soy oil, and corn starch:soy oil, respectively, for the dietary treatments fed from d 15 to 22 in Table 1. For the TD in experiment 2, barley and wheat were added at 100 or 200 g/kg of diet to partly replace corn, soybean meal, corn starch, and soy oil in such a way as to maintain the same ratio of corn, soybean meal, corn starch, and soy oil across the experimental diets as in experiment 1. Chemical Analyses Wheat, barley, WDDGS1, and WDDGS2, diets, ileal digesta, and excreta samples from the 2 experiments were placed at 105 C in a drying oven (Precision Scientific Co., Chicago, IL) for 24 h for DM determination. Nitrogen was determined using the combustion method (Leco model FP-2000 N analyzer, Leco Corp., St. Joseph, MI) using EDTA as a calibration standard. Crude fat was determined by ether extraction (method for crude fat; AOAC International, 2000). Gross energy was determined in a bomb calorimeter (Parr 1261 bomb calorimeter, Parr Instruments Co., Moline, IL) using benzoic acid as a calibration standard. Samples were digested in concentrated nitric acid and 70% perchloric

4 acid to solubilize Ca and P. The concentration of P in the supernatant was measured using a kit (Sigma kit # 670, Sigma Diagnostics Inc., St. Louis, MO) as described by Onyango et al. (2004). The Ca content of the supernatant was determined using flame atomic absorption spectrometry (Varian FS240 AA Varian Inc., Palo Alto, CA). Samples were digested [nitric/perchloric wet ash, method A (a); AOAC International, 2000] and Cr concentration was determined (Spectronic 21D, Milton Roy Company, Rochester, NY) using the method of Fenton and Fenton (1979). Barley, wheat, and WDDGS samples were analyzed for neutral detergent fiber and acid detergent fiber [method (A, B, C, D); AOAC International, 2000], for Ca and P [methods (A, B, C); AOAC International, 2000], and for amino acids [method E (a, b, c); AOAC International, 2000] at the University of Missouri Experiment Station Chemical Laboratories, Columbia. Calculations and Statistics The ileal digestibility or total tract metabolizability coefficients (C) of nutrients or energy were calculated as C = 1 [(Cd/Co) (Eo/Ed)], where Cd is the concentration of Cr in the diet; Co is the concentration of Cr in the ileal digesta or excreta output; Eo is the concentration of nutrient or energy in the ileal digesta or excreta output; and Ed is the concentration of nutrient or energy in the diet (Adeola and Zhai, 2012). Metabolizable energy (kcal/kg) of the diet was calculated as the product of C and the gross energy concentration (kcal/kg) of the diet. Because catabolic compounds in excreted N can contribute to energy loss, ME was corrected to zero N retention using a factor of 8.22 kcal/g (Hill and Anderson, 1958) as ME n = ME (8.22 N ret ), where N ret is N retention in g/kg of DM intake. The N ret was calculated as N ret = N i (N o Cd/Co), where N i and N o are the N concentrations (g/kg of DM) in the diet and excreta, respectively. The coefficients (C) of ME for reference diet, test diets, and test ingredient are Crd, Ctd, and Cti, respectively. The proportional contribution of energy by the reference diet and test ingredient to the test diet are Prd and Pti, respectively, and by definition Prd + Pti = 1 or Prd = 1 Pti. The assumption of additivity in diet formulation implies that Ctd = (Crd Prd) + (Cti Pti); solving for Cti gives Cti = [Ctd (Crd Prd)] Pti. Substituting 1 Pti for Prd gives Cti = [Crd + (Ctd Crd) Pti)]. The product of Cti at each level of test ingredient substitution rate (100 or 200 g/kg), kilograms of dry test ingredient intake (product of 0.1 or 0.2 and dry feed intake), and the gross energy of test ingredient is the test ingredient-associated ME, or nitrogen-corrected metabolizable energy intake in kilocalories. Growth performance and digestibility data for the 2 experiments were analyzed using the GLM procedures of SAS Institute (2006) in a randomized complete block ENERGY VALUES USING REGRESSION METHOD design. The effects of increasing levels of WDDGS1 or WDDGS2 in TD in experiment 1 and barley or wheat in TD in experiment 2 were compared using linear and quadratic contrasts. Regression of the test ingredientassociated IDE, ME, or ME n intake in kilocalories against kilograms of test ingredient intake for cage of birds was conducted using multiple linear regression for each experiment using the following SAS statements: Proc GLM; class TI; Model Y = TI*DMintake/solution; the solution option was used to generate intercept and slopes. Y is test ingredient-associated IDE, ME, or ME n intake in kilocalories, TI is test ingredient (coded as WDDGS1 or WDDGS2 in experiment 1; and barley or wheat in experiment 2), DMintake is test ingredient intake in kilograms of DM, which is used as a regressor. Statistical significance was determined at an α level of RESULTS 1931 The analyzed nutrient and energy composition of the 2 WDDGS samples, barley, and wheat used in the current study are presented in Table 2. There were very little variations in DM, GE, N, crude fat, fiber fractions, and amino acid composition of the 2 WDDGS samples. Except for fiber fractions, the analyzed nutrient and energy composition showed similar composition for barley and wheat (Table 2). Addition of either of the 2 WDDGS samples to the reference diet did not affect the growth performance of birds from d 15 to 22 posthatch. The average initial BW, 7-d weight gain, feed intake, and gain/feed were 328 g, 355 g, 492 g, and 0.72, respectively. The data presented in Table 3 show the digestibilities and metabolizabilities of DM, N, and energy of experimental diets fed from d 15 to 22 posthatch. The DM and energy metabolizability coefficients, IDE, ME, and ME n values were higher in the RD relative to the TD. There was a linear decrease (P < 0.01) in diet DM metabolizability with increasing levels of WDDGS1 and WDDGS2. Energy metabolizability followed a pattern similar to that of DM metabolizability. Energy metabolizability linearly decreased (P < 0.05) with increasing level of both WDDGS. Total tract N utilization coefficient decreased linearly (P < 0.05) with increasing levels of WDDGS2, but there was no significant effect of WDDGS1 on the total tract N utilization of diets. Diet IDE values ranged from 3,400 to 3,907 kcal/kg of DM of diets and linearly decreased (P < 0.01) with increasing levels of either WDDGS sample in the diets (Table 3). Diet ME followed a similar trend as IDE with a linear decrease (P < 0.01) as the levels of either WDDGS sample in the TD increased. A quadratic effect (P < 0.05) was also observed in the diets containing WDDGS2. On the average, nitrogen correction resulted in a 5% reduction in ME of the diets. The ME n values ranged between 3,067 and 3,395 kcal/kg of experimental diets. Similar to ME, linear decrease (P < 0.01) in diet ME n was ob-

5 1932 Bolarinwa and Adeola Table 3. Ileal digestibility and total tract utilization of DM, nitrogen, and energy by birds offered experimental diets d 15 to 22 posthatch in experiment 1 1 Diet WDDGS1, g/kg WDDGS2, g/kg P-value Item Reference SEM L 2 Q 2 L 3 Q 3 Ileal digestibility coefficient DM < < Nitrogen < < Energy < < Ileal digestible energy, kcal/kg 3,907 3,609 3,404 3,650 3, < < Total tract metabolizability coefficient DM < Nitrogen < Energy < < N-corrected energy < < ME, kcal/kg 3,555 3,399 3,222 3,465 3, < < MEn, kcal/kg 3,395 3,228 3,067 3,306 3, < < Data are means of 8 replicate cages with 8 birds per cage. 2 Linear (L) and quadratic (Q) contrasts for wheat dried distillers grains with solubles 1 (WDDGS1). 3 Linear (L) and quadratic (Q) contrasts for wheat dried distiller grains with solubles 2 (WDDGS2). Table 4. Ileal digestibility and total tract utilization of DM, nitrogen, and energy by birds offered experimental diets d 15 to 22 posthatch in experiment 2 1 Diet Barley, g/kg Wheat, g/kg P-value Item Reference SEM L 2 Q 2 L 3 Q 3 Ileal digestibility coefficient DM Nitrogen Energy < Ileal digestible energy, kcal/kg 3,639 3,596 3,404 3,629 3, < Total tract metabolizability coefficient DM Nitrogen Energy N-corrected energy ME, kcal/kg 3,482 3,557 3,363 3,468 3, <0.001 < MEn, kcal/kg 3,311 3,408 3,216 3,315 3, <0.001 < Data are means of 8 replicate cages with 8 birds per cage. 2 Linear (L) and quadratic (Q) contrasts for barley. 3 Linear (L) and quadratic (Q) contrasts for wheat.

6 served in diets containing both WDDGS samples, with a quadratic (P < 0.05) also observed with WDDGS2 inclusion (Table 3). The test diets containing barley or wheat at 100 or 200 g/kg did not affect the growth performance of birds from d 15 to 22 posthatch. The average initial BW, 7-d weight gain, feed intake, and gain/feed were 328 g, 330 g, 485 g, and 0.68, respectively. Barley addition to the RD linearly reduced (P < 0.01) ileal digestibility of DM, N, and energy and IDE, whereas wheat addition did not affect any of the ileal digestibility measurements for the test diets (Table 4). Neither of the cereal grains had any significant effect on N utilization. Energy metabolizability of the TD decreased (P < 0.05) with barley addition but increased (P < 0.05) with wheat addition. Both ME and ME n of the TD decreased (P < 0.05) with barley addition, but wheat addition did not affect these response criteria (Table 4). Table 5 shows the regression equations relating test ingredient-associated energy intake to intake of test ingredients for the determination of IDE, ME, and ME n of the 2 WDDGS samples, barley, and wheat evaluated in the current study. In experiment 1, the IDE were 2,001 kcal/kg of DM for WDDGS1 and 1,830 kcal/kg for WDDGS2; the ME were 2,644 kcal/kg of DM for WDDGS1 and 2,215 kcal/kg for WDDGS2. And ME n were 2,464 kcal/kg of DM for WDDGS1 and 2,092 kcal/ kg for WDDGS2. In experiment 2, IDE values were 2,364 kcal/kg of DM for barley and 3,413 kcal/kg of DM for wheat; ME values were 2,894 kcal/kg of DM for barley and 3,513 kcal/kg of DM for wheat. For ME n, regression-generated values were 2,841 kcal/kg of DM for barley and 3,372 kcal/kg of DM for wheat (Table 5). DISCUSSION Mitigating high feed costs for broiler meat production, of necessity, requires adequate nutritional characterization of feed ingredients that may be cost-effective in a variety of production situations. The objective of the current studies was to determine the energy value of wheat distillers dried grains with solubles, barley, and wheat for broiler chickens. Because these feed ingredients may be formulated into broiler chicken diets, knowledge of their energy value is crucial for cost-effective diets. The chemical composition of the 2 WD- DGS samples evaluated in the current experiments are similar to those reported by (Nyachoti et al., 2005; Widyaratne and Zijlstra, 2007; Lan et al., 2008). Furthermore, the chemical composition of the 2 WDDGS samples evaluated in the current experiments are similar to the mean of 10 WDDGS samples reported recently in studies conducted to evaluate the energy value of 10 samples of WDDGS by Cozannet et al. (2010). Chemical composition similar to those of barley evaluated in the current study have been reported (Ragland et al., 1997; Zijlstra et al. 2011). Furthermore, wheat chemical composition is also similar to that reported by Kim et al. (2003) and Péron et al. (2005). ENERGY VALUES USING REGRESSION METHOD 1933 Inclusion of WDDGS negatively affected the IDE, ME, and ME n of diets, which is consistent with the findings of Cozannet et al. (2010). This decrease may not be attributed to energy expenditure due to N excretion as WDDGS1 inclusion did not have any significant effect on N utilization. Because there is no available information on the starch content and the color rating of the WDDGS samples used in the current study, it is uncertain whether this decrease in energy digestibility is directly associated with factors such as heat processing, which has been reported to negatively affect the digestibility of DDGS (Fastinger et al., 2006) and low residual starch content which is associated with Maillard reactions, producing brown compounds with lower nutritional values. However, the 2 WDDGS used in the current experiment were dark in color and had a slightly burnt odor, which suggests that the WDDGS may have been overheated during the drying process (Cromwell et al., 1993; Fastinger and Mahan, 2006). The concentration of lysine as a percentage of CP could be used as an indicator of heat damage in corn DDGS (Stein and Shurson, 2009). An average percent lysine concentration in CP for undamaged corn DDGS has been reported to be between 3.1 and 3.3 but could be as low as 2.1 in heat-damaged corn DDGS samples. In the current studies, percent lysine concentration in CP were 2.1 and 2.0, for WDDGS1 and WDDGS2, respectively, and this suggests that the 2 WDDGS samples used in the current study may have been heatdamaged during the production process. The observed decrease in IDE, ME, and ME n of diets could be attributed more to the high fiber content of WDDGS. Starch removal during fermentation concentrates other components, including acid detergent fiber, neutral detergent fiber, and nonstarch polysaccharides, that are not converted into ethanol. This results in the crude fiber content of WDDGS being approximately 3 times that of wheat. The culprit for lower digestibility of nutrients in DDGS is usually recognized as the higher fiber content (Thacker and Widyaratne, 2007; Adeola et al., 2010) for its low digestibility in itself and its negative influence on digestion of other nutrients. Because fiber digestibility in DDGS is poor, it is likely that the decrease in IDE, ME, and ME n of diets observed in the current study may be attributed to the greater concentration of fiber in WDDGS-containing TD relative to the RD, coupled with the low fiber digestibility in the gastrointestinal tract relative to the RD. Because energy utilization is affected by age, species, and protein quality of a feed, it is necessary to correct ME for nitrogen retention that occurred during the assay period. In the current study, nitrogen correction resulted in a 4 to 5% reduction in the ME of diets used in experiments 1 and 2 and 6 to 7% in the ME value of the WDDGS samples. For barley and wheat, nitrogen correction resulted in a 2 to 4% reduction in ME of the samples. In studies with ducks, Adeola et al. (1997, 2007) reported between 2 and 5% and 4 and 6% reduction in energy value after nitrogen correction. McNab

7 1934 Bolarinwa and Adeola Table 5. Regression equations relating test ingredient-associated energy intake to intake of wheat dried distillers grains with solubles (WDDGS1) or WDDGS2 in experiment 1 and barley or wheat in experiment 2 1 Item Regression equation r 2 SD Experiment 1 IDE Y = 8 (11) (186) WDDGS (177) WDDGS ME Y = 0.1(11) (202) WDDGS (192) WDDGS ME n Y = 1 (11) (193) WDDGS (184) WDDGS Experiment 2 IDE Y = 8 (10) (195) Barley (181) Wheat ME Y = 3 (12) (234) Barley (216) Wheat ME n Y = 6 (12) (218) Barley (202) Wheat Values in parentheses are SE; Y is in kilocalories, intercept is in kilocalories, and the slopes are in kilocalories/ kg of DM. and Blair (1988) observed a reduction of between 7 and 10% in energy value due to nitrogen correction. Although both WDDGS samples used in experiment 1 had very similar CP and amino acid composition, WD- DGS2 negatively affected N utilization whereas WD- DGS1 did not. The reason for this is not known, but the effect of WDDGS2 on N utilization in this experiment is similar to what was observed by Leytem et al. (2008) and Cozannet et al. (2010). Formulating barley into the test diets depressed DM and energy digestibility in experiment 2. Consequently, a linear decrease in diet DE, ME, and ME n were observed with increasing levels of barley. This may be due to one or more of several factors. One of the major concerns over the inclusion of barley in poultry diet is that of viscosity arising from its high β-glucan content. Adeola and Bedford (2004) observed that high viscosity diet (wheat-based) significantly reduced the digestibility of fat, starch, N, and energy in the ileum of ducks. This viscosity-induced negative effect on digestibility, they said, could increase the passage time of digesta, thereby encouraging the proliferation of microflora in the small intestine. They also noted that the viscosityinduced increase in microbial population in the gastrointestinal tract could increase the deconjugation of bile acids, which may impair the entero-hepatic recirculation of bile acid and hence reduce fat digestion and thus affect energy digestibility. Although we did not analyze for NSP in our diets, calculations based on previous studies were used to calculate the amount of NSP in the diets. Bach-Knudsen (1997) analyzed for the level of NSP in various plant feedstuffs and reported that barley contains about 186 g/kg of NSP. Based on this value, the estimated NSP content coming from barley in these diets were 18.6 and 37.2 g/kg for diets containing 100 and 200 g/kg of barley, respectively. In experiment 2, wheat addition to the RD increased the metabolizability of DM and energy digestibility perhaps due to the lower energy metabolizability coefficient (0.78) of the RD used relative to wheat. In this context, energy metabolizability coefficient for wheat derived using the regression method is Notionally, the addition of a test ingredient with a higher energy utilization coefficient to the reference diet will replace the less utilizable portion, and as a consequence, increase overall energy utilization in the test diets. The IDE, ME, and ME n values obtained using the regression method for WDDGS1 were 2,001; 2,644; and 2,464 kcal/kg of DM, respectively. These values are somewhat higher than those for WDDGS2 at 1,830; 2,215; and 2,092 kcal/kg of DM, respectively. Despite the similarity in chemical composition of the 2 samples of WDDGS, there was about 400 kcal/kg difference in their ME values. This emphasizes the importance of energy and nutrient utilization studies with animals, as energy availability must be known to fully evaluate the significance of concentration. Recently, in experiments conducted to determine the energy value of 10 samples of WDDGS, Cozannet et al. (2010) reported a range of ME between 2,070 and 2,663 kcal/kg of DM and ME n between 2,041 and 2,648 kcal/kg of DM. The ME of 2,215 and 2,644 kcal/kg of DM for WDDGS2 and WD- DGS1 are within the range reported by Cozannet et al. (2010). The IDE, ME, and ME n values were 2,364; 2,894; and 2,841 kcal/kg of DM, respectively, for barley. Kromann et al. (1976) and Robinson et al. (1965) reported values lower than those observed in this study, and this can be due to factors such as variety of barley used and the nutrient composition of the barley used. For barley with 89% DM, NRC (1994) reported ME n of 2,940 kcal/kg of DM, which is similar to that determined in the current study. The determined ME and ME n of wheat evaluated in the current study were 3,513 and 3,372 kcal/kg of DM, respectively, which fall within the range of values reported by Farrell (1981). The ME values ranging between 3,050 and 3,770 kcal/kg of DM for 33 samples of Australian wheat in chickens were reported by Farrell (1981). Furthermore, NRC (1994) reported an ME n of 3,500 kcal/kg of DM of wheat. In conclusion, the current studies show that wheat distillers dried grains with solubles is a potential energy source for the broiler chicken and provide energy values for this co-product of wheat processing into ethanol as well as energy values for barley and wheat.

8 ACKNOWLEDGMENTS The authors gratefully acknowledge Pat Jaynes and Jason Fields (Purdue University, West Lafayette, IN) for their varied roles in the conduct of and contribution to this study. REFERENCES Adeola, O., and M. R. Bedford Exogenous dietary xylanase ameliorates viscosity induced anti-nutritional effects in wheatbased diets for White Pekin ducks (Anas platyrinchos domesticus). Br. J. Nutr. 92: Adeola, O., and K. E. Ileleji Comparison of two diet types in the determination of metabolizable energy content of corn distillers dried grains with solubles for broiler chickens by the regression method. Poult. Sci. 88: Adeola, O., J. A. Jendza, L. L. Southern, S. Powell, and A. Owusu- Asiedu Contribution of exogenous dietary carbohydrases to the metabolizable energy value of corn distillers grains for boiler chickens. Poult. Sci. 89: Adeola, O., C. M. Nyachoti, and D. Ragland Energy and nutrient utilization responses of ducks to enzyme supplementation of soybean meal and wheat. Can. 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