Compositional effects of corn distillers dried grains with solubles with ...

The Professional Animal Scientist 31 (2015):485–496; http://dx.doi.org/10.15232/pas.2015-01444 ©2015 American Registry of Professional Animal Scientists

Ccorn ompositional effects of distillers dried grains

with solubles with variable oil content on digestible, metabolizable, and net energy values in growing pigs1 B. J. Kerr,*2 N. K. Gabler,† and G. C. Shurson‡ *USDA-ARS-National Laboratory for Agriculture and the Environment, Ames, IA 50011; †Department of Animal Science, Iowa State University, Ames 50011; and ‡Department of Animal Science, University of Minnesota, St. Paul 55108

ABSTRACT Two experiments were conducted in growing-finishing pigs to determine the DE and ME (Exp. 1, 96.3 kg of BW) and NE (Exp. 2, 45.4 kg of BW) content of corn distillers dried grains with solubles (C-DDGS), and to refine or develop DE, ME, and NE prediction equations based This research was financially supported by the National Pork Board (Des Moines, IA). Mention of a trade name, proprietary product, or specific equipment does not constitute a guarantee or warranty by the USDA, Iowa State University, or the University of Minnesota and does not imply approval to the exclusion of other products that may be suitable. The authors gratefully acknowledge the assistance of K. Ruge, C. Stoffel, and M. Buyck (Iowa State University, Ames) and J. Cook (USDA-ARS, Ames, IA) with sample collection and laboratory analysis. The USDA is an equal opportunity provider and employer. 2 Corresponding author: brian.kerr@ars. usda.gov 1

on chemical composition of C-DDGS. Composition of the 6 C-DDGS sources varied (ash, 4.71 to 5.63%; CP, 29.65 to 32.21%; ether extract, 6.99 to 13.34%; NDF, 38.27 to 39.58%; total dietary fiber, 31.12 to 32.81%; DM basis), with the determined DE ranging from 3,836 to 4,038 kcal/kg of DM, ME from 3,716 to 3,893 kcal/kg of DM, and NE from 2,107 to 2,310 kcal/kg of DM. Regardless of the range in C-DDGS composition and the resulting DE, ME, or NE value, no chemical parameter measured (GE, CP, starch, total dietary fiber, NDF, ADF, hemicellulose, ether extract, or ash) was significant at P ≤ 0.15 to be retained in the regression model to predict DE, ME, or NE content in the C-DDGS sources evaluated. Apparent total-tract digestibilities of several nutritional components were also measured for comparative purposes but were not included in the prediction model. On average, the C-DDGS used in these studies contained 3,931, 3,793, and 2,207 kcal of DE, ME, and NE per kilogram of DM,

respectively. These results suggest that C-DDGS composition and subsequent DE, ME, and NE can be highly variable and that a wider range in ingredient chemical composition and DE, ME, and NE values, as well as more C-DDGS sources, appear to be necessary to generate energy-prediction equations than used in the current experiments. Key words: corn distillers dried grains with solubles, ether extract, net energy, pig, prediction equation

INTRODUCTION Corn dried distillers grains with solubles (C-DDGS) have typically contained 10 to 11% ether extract (EE), with a ME content similar to corn (Stein and Shurson, 2009). However, recent implementations of oil-extraction technologies by most United States ethanol plants have led to the production of C-DDGS with a wider range of energy and nutrient

486 composition (Anderson et al., 2012; Kerr et al., 2013). Because lipids contain 2.25-times more energy than carbohydrates, removal of lipids likely reduces the DE, ME, and NE content in C-DDGS, which can affect its economic value and dietary inclusion rate in swine feed formulations. In addition, removal of lipids would be expected to concurrently concentrate other components in C-DDGS such as fiber and ash, which have been shown to reduce the caloric value of feedstuffs consumed by an animal (Fernandez and Jorgensen, 1986; Degen et al., 2007; Kim et al., 2012). Several studies have been published (Stein et al., 2006; Jacela et al., 2011; Kerr et al., 2013) that have determined the DE and ME content of C-DDGS. Recent studies have also developed prediction equations based on chemical analysis to estimate DE and ME content (Pedersen et al., 2007; Anderson et al., 2012; Kerr et al., 2013). In addition, Urriola et al. (2014) conducted a cross-study validation of these and other published equations for C-DDGS. Only one study (Gutierrez et al., 2014) has estimated the NE content of C-DDGS, and no study has determined whether prediction equations to estimate NE of C-DDGS content can be based on chemical analysis. Therefore, the objectives of this study were to determine whether the chemical composition of C-DDGS samples varying in energy and nutrient content could be used to develop or refine DE, ME, and NE prediction equations.

MATERIALS AND METHODS Animal Management The Institutional Animal Care and Use Committee at Iowa State University (Ames) approved all experimental protocols. Two experiments (Exp. 1 and Exp. 2) were conducted using gilts that were offspring of PIC Camborough 22 sows × L337 boars (Pig Improvement Company, Hendersonville, TN). In each experiment,

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gilts were fed a standard diet based on corn and soybean meal before being assigned to experimental diets. Gilts were weighed at the beginning of the adaptation period and end of each collection period for both experiments.

Exp. 1 In Exp. 1, 2 groups of 24 and 1 group of 20 gilts (n = 68; final BW = 96.3 kg, SD = 10.1 kg) were housed individually in metabolism crates (0.7 × 1.5 m) that allowed for separate but total collection of feces and urine. Crates were equipped with a stainless steel feeder and a nipple waterer, to which the pigs had ad libitum access. Based on past experience in digestibility studies (Lammers et al., 2008; Kerr et al., 2009, 2013; Anderson et al., 2012), each pig was used as their own control (i.e., fed the basal diet), and thus, 2 feeding periods were used within each group. To accomplish this, a switch-back design was used. During period 1, pigs in crates 1 through 12 were first fed the basal diet while pigs in crates 13 through 24 were first fed the 60% basal plus 40% C-DDGS dietary treatments. In contrast, during period 2, pigs in crates 1 through 12 were fed the 60% basal plus 40% C-DDGS treatments while pigs in crates 13 through 24 were fed the basal diet. Use of this experimental design concept is supported by Jacobs et al. (2013), who reported that use of covariates in digestibility studies are one way to reduce animalto-animal variation. Within this design, gilts were assigned randomly to either the basal or a C-DDGScontaining diet, resulting in a total of 68 observations for pigs fed the basal diet and 8 or 12 observations for pigs fed the C-DDGS sources. Feed was offered at approximately 3% of BW during each 9-d adaption and 4-d collection period. During the time-based, 4-d total fecal and urine collection period, stainless steel screens were placed under each metabolism crate for total fecal collection and stainless steel buckets

containing 25 mL of 6 N HCl were placed under each crate for the total urine collection. Feces and urine were collected twice daily and stored at 0°C until the end of the collection period. Feces were pooled by pig over the 4-d period, dried in a 70°C forced-air oven, weighed, and ground through a 1-mm screen, with a subsample taken for analysis. Likewise, urine samples were pooled by pig over the 4-d period, thawed at the end of the collection period, and weighed, with a subsample collected for analysis.

Exp. 2 For Exp. 2, a separate group of 79 gilts was used in a 35-d feeding trial. Pigs (initial BW = 45.3 kg, SD = 4.2 kg) were allotted randomly to individual pens (0.57 × 2.21 m), allowed free access to feed and water, and maintained in rooms with 24-h lighting. Whole body composition, lean, lipid, and bone mineral contents were predicted using a Hologic Discovery A Dual Energy x-ray Absorptiometry (DXA; Bedford, MA) as described by Suster et al. (2003, 2004). The daily NEm for each pig was calculated as 179 kcal/kg of BW0.60·d−1 (Noblet et al., 1994), with protein assumed to contain 5.54 kcal/g and lipid assumed to contain 9.34 kcal/g (Birkett and DeLange, 2001). Conversion of whole body DXA-predicted lean to whole body predicted protein was calculated as 4.59 g of lean = 1 g of whole body protein based on body composition and DXA calibration data determined previously (N. Gabler, unpublished data). Initial and final (d-35) body composition was obtained on each pig using DXA following an overnight feed withdrawal and short transport to the scanning room. For each scan, pigs were weighed, anesthetized with an i.m. injection of telazol:ketamine:xylazine (2:1:2, 4.4 mg/kg, 2.2 mg/kg, 4.4 mg/ kg, respectively) at a dose of 1 mL per 45.5 kg of BW and placed prone on the scan table with hind legs and fore legs extended. Each pig was then DXA scanned and allowed to recover

Net energy of distillers dried grains with solubles

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Table 1. Methods of analysis Measurement Bulk density1 GE1 Carbon, N, and S1 Particle size1 ADF2 Ash2 CP2 DM2 Ether extract2 Fatty acids2 FFA2 Lysine2 Minerals2 NDF2 Peroxide value2 Thiobarbituric acid2 Total starch2 Total dietary fiber3 Aflatoxin B1, B2, G1, G24 Deoxynivalenol4 Fumonisin B1, B2, B34 Ochratoxin A4 T-2 Toxin4 Zearalenone4

Method USDA (1953) Isoperibol bomb calorimeter (Model 1281, Parr Instrument Co., Moline, IL) Thermocombustion (VarioMax CNS Analyzer, Elementar Analysensysteme GmbH, Hanau, Germany) Baker and Herrman (2002) AOAC International (2005) official method 973.18 (A–D) AOAC International (2005) official method 942.05 AOAC International (2005) official method 990.03 AOAC International (2005) official method 934.01 AOAC International (2005) official method 920.39 (A), petroleum ether AOAC International (2005) official method 969.33; 963.22 AOAC International (2005) official method 940.28 AOAC International (2005) official method 982.30 E (a) AOAC International (2005) official method 985.01 (A–D) Holst (1973) AOAC International (2005) official method 940.28 AOCS (2011) official method Cd 19–90 AACC International (1976); approved method 76–13.01; modified: starch assay kit (Kit STA-20; Sigma, St. Louis, MO) AOAC International (2005) official method 991.43 AOAC International (2005) official method 994.08 Trucksess et al. (1998) AOAC International (2005) official method 995.15 AOAC International (2005) official method 2000.3 Croteau et al. (1994) MacDonald et al. (2005)

Analyzed by USDA-ARS, Ames, Iowa. Analyzed by University of Missouri, Columbia. 3 Analyzed by Eurofins, Des Moines, Iowa. 4 Analyzed by Trilogy Analytical Laboratory, Washington, Missouri. 1 2

(~3 h) before being transported back to its barn. Whole body protein, lipid, and bone deposition was calculated by subtracting initial body composition from final body composition. The NE of each C-DDGS source was calculated by subtracting the NE contributed by the basal diet from the total NE of the diet containing a particular C-DDGS source. In addition, a fresh fecal sample was obtained on d 31 to determine diet DE content using indirect marker digestibility (Jacobs et al., 2013) and to compare this value to the dietary DE determined in Exp. 1.

Diets All C-DDGS samples were analyzed for a variety of analytes at various

laboratories as described in Table 1. The 6 sources of C-DDGS were selected (Table 2) based on their range in EE (6.99 to 13.34%, DM basis) and particle size (310 to 544 μm). Each experiment used the same corn–soybean meal basal diet, which along with each C-DDGS source were analyzed comprehensively for various physical and chemical components. Depending upon treatment, pigs were either fed 100% of the corn–soybean meal basal diet or a test diet that contained 60% of the basal diet and 40% of a specific C-DDGS sample, except for source B, which was included in the diet at 30% (70% basal) due to limited quantity of product (Table 3). All diets were fed in meal form, and titanium dioxide was included in all diets as an indigestible marker. Test

ingredients were not ground to a constant particle size to reflect particle sizes that are typical of commercial conditions and to allow the inclusion of particle size as a factor in predicting DE, ME, and NE when developing prediction equations.

Chemical Analysis and Calculations The basal diet, each C-DDGS sample, and all feces were ground through a 1-mm screen before chemical analysis. To determine DE and ME content, GE of the diets and C-DDGS, feces, and urine samples were determined using an isoperibol bomb calorimeter with benzoic acid used as a standard. For urine, 1 mL of filtered urine was added to 0.5 g

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Table 2. Analyzed composition of basal diet and corn distillers dried grains with solubles (C-DDGS) sources, DM basis C-DDGS source Item Bulk density, g/cm Particle size,1 μm DM,2 % GE,1 kcal/kg CP,2 % Lysine,2 % Total starch,2 % TDF,3 % NDF,2 % ADF,2 % Hemicellulose,4 % Ash,2 % Chloride,2 % Phosphorus,2 % Potassium,2 % Sodium,2 % Sulfur,2 % Ether extract,2 % Myristic, 14:02,5 Palmitic, 16:0 Palmitoleic, 16:1 Stearic, 18:0 Oleic, 18:1 Linoleic, 18:2 Linolenic, 18:3 Arachidonic, 20:4 Eicosapentaenoic, 20:5 Docosapentaenoic, 22:5 Docosahexaenoic, 22:6 FFA,2 % Thiobarbituric acid, absorbance2 Peroxide value,2 mEq/kg Mycotoxins6 Aflatoxin B1, μg/kg Aflatoxin B2, μg/kg Aflatoxin G1, μg/kg Aflatoxin G2, μg/kg Deoxynivalenol, mg/kg Fumonisin B1, mg/kg Fumonisin B2, mg/kg Fumonisin B3, mg/kg Ochratoxin A, μg/kg T-2 Toxin, μg/kg Zearalenone, μg/kg 1

3

Basal

A

B

C

D

E

F

0.563 536 88.54 4,267 17.04 1.02 50.44 10.84 9.32 3.35 5.96 4.86 0.34 0.50 0.72 0.16 0.23 3.14 0.00 14.34 0.00 2.07 25.55 55.05 2.37 0.00 0.00 0.00 0.00 1.32 45.65 22.53

0.492 544 88.66 5,227 29.65 1.07 2.50 31.47 38.27 11.48 26.79 4.79 0.16 0.83 1.16 0.19 0.56 13.34 0.00 15.02 0.14 2.02 25.02 54.54 1.73 0.00 0.00 0.00 0.14 1.88 11.73 10.21

0.508 514 88.88 5,094 32.00 1.14 2.33 31.62 38.49 12.14 26.35 4.71 0.16 0.87 1.14 0.14 0.54 10.41 0.00 14.08 0.15 2.10 25.41 55.17 1.61 0.00 0.00 0.00 0.18 1.10 8.19 13.27   1.35 ND ND ND 0.56 3.26 0.56 0.23 ND ND ND

0.477 491 89.34 5,052 31.59 1.13 3.82 31.12 39.58 11.60 27.98 5.38 0.17 0.92 1.18 0.18 0.73 9.11 0.08 14.20 0.13 1.90 24.40 56.29 1.65 0.00 0.00 0.00 0.16 1.25 14.04 3.46

0.516 310 89.80 4,981 30.58 1.18 4.93 32.41 30.95 8.90 22.05 5.63 0.21 0.90 1.29 0.26 1.10 8.01 0.09 15.05 0.19 2.81 27.15 51.39 1.52 0.00 0.00 0.00 0.23 0.99 8.15 6.73   5.12 ND ND ND 0.22 3.67 0.67 0.22 ND ND ND

0.508 338 90.52 4,918 32.21 1.15 4.40 32.81 31.05 8.55 22.50 5.51 0.21 0.94 1.27 0.18 1.05 6.99 0.00 14.08 0.14 2.13 25.73 54.78 1.62 0.00 0.00 0.00 0.28 0.72 10.85 4.23

0.492 368 91.28 5,155 29.83 1.10 4.68 32.10 27.84 8.55 19.29 5.53 0.19 0.85 1.30 0.19 0.11 11.38 0.06 14.30 0.15 2.21 25.81 54.29 1.54 0.00 0.00 0.00 0.20 1.21 5.90 2.77

ND ND ND ND 0.45 0.34 ND ND ND ND ND

ND ND ND ND 0.23 0.34 ND ND ND ND ND

ND ND ND ND 1.57 4.93 0.78 0.34 ND ND 77.12

Analyzed by USDA-ARS, Ames, Iowa. Analyzed by University of Missouri, Columbia. 3 Analyzed by Eurofins, DesMoines, Iowa. 4 Calculated as NDF − ADF. 5 Fatty acid composition is expressed as a percentage of total fat. 6 Analyzed by Trilogy Analytical Laboratory, Washington, Missouri. ND = not detected or below detection limit. 1 2

ND ND ND ND 0.88 1.66 0.22 ND ND ND ND

ND ND ND ND 0.77 1.64 0.22 ND ND ND ND

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of dried cellulose and subsequently dried at 50°C for 24 h. Urine addition and subsequent drying was repeated 3 times, for a total of 3 mL, over a 72-h period before urinary GE determination. Gross energy in cellulose was also determined, and urinary GE was calculated by subtracting the GE content of cellulose from the GE content of samples containing both urine and cellulose. Gross energy intake was calculated as the product of GE content of the treatment diet and the actual feed intake over the 4-d collection period. Within a specific assay diet, the DE and ME of each C-DDGS source were calculated by subtracting the DE or ME contributed by the basal diet from the DE or ME of the diet containing a particular C-DDGS source. All energy values are reported on a DM basis. Similar to the calculations for energy, apparent total-tract digestibility of ADF, carbon, DM, EE, N, NDF, phosphorus, and S of each C-DDGS source were calculated by subtracting the respective analyte contributed by the basal diet from the same analyte of the diet containing that particular C-DDGS source. Digestibility coefficients were then determined by dividing grams of component digested

by the grams of component consumed and reported on a percentage basis.

Statistical Analysis Using the individual pig as the experimental unit, data were subjected to ANOVA using Proc GLM with group, period, and treatment in the model for Exp. 1, or treatment in the model in Exp. 2 (SAS Institute Inc., Cary, NC), with treatment means reported as least squares means. Using Proc REG, stepwise regression was used to determine the effect of physical and chemical analytes among C-DDGS sources on predicting DE and ME in Exp. 1 or on NE for Exp. 2, and variables with P-values ≤0.15 were retained in the model. The R2 and the SE of the estimates were used to define the best-fit equation, if applicable.

RESULTS AND DISCUSSION Overview of Experimental Approach The primary objectives of these experiments were to obtain C-DDGS samples with a range in EE to validate DE and ME values for C-DDGS

from our previous work (Anderson et al., 2012; Kerr et al., 2013), validate equations to predict DE and ME of C-DDGS from compositional analysis, as well as determine the NE content and develop a NE prediction equation for C-DDGS. The range of EE content among the C-DDGS sources evaluated in the current study ranged from 6.99 to 13.34% EE on a DM basis, which was slightly greater than sources evaluated in our previous work (8.56 to 13.23% EE, DM basis; Kerr et al., 2013) and was greater than the range reported by others (Stein et al., 2006, 2009; Pedersen et al., 2007; Anderson et al., 2012). Consequently, it was assumed that this range in EE content among sources would have been adequate to generate equations to predict DE, ME, and NE based on chemical composition. Results from recent studies evaluating EE content of C-DDGS sources in broilers have indicated that a wide range of chemical composition is necessary for developing energyprediction equations (Rochell et al., 2011; Meloche et al., 2013, 2014). Other compositional characteristics of the C-DDGS sources used in the current experiment are within the ranges reported by researchers listed

Table 3. Composition of experimental diets (%), as-fed basis1 C-DDGS source Item

Basal

A

B

C

D

E

F

Corn Soybean meal C-DDGS Monocalcium phosphate Limestone Sodium chloride Trace mineral mix2 Vitamin mix3 l-Lysine·HCl Titanium dioxide4

79.35 17.90 – 0.71 0.71 0.35 0.20 0.15 0.13 0.50

47.60 10.74 40.00 0.43 0.43 0.21 0.12 0.09 0.08 0.30

55.54 12.53 30.00 0.50 0.50 0.25 0.14 0.11 0.09 0.35

47.60 10.74 40.00 0.43 0.43 0.21 0.12 0.09 0.08 0.30

47.60 10.74 40.00 0.43 0.43 0.21 0.12 0.09 0.08 0.30

47.60 10.74 40.00 0.43 0.43 0.21 0.12 0.09 0.08 0.30

47.60 10.74 40.00 0.43 0.43 0.21 0.12 0.09 0.08 0.30

Basal diet was formulated to contain 0.50% Ca and 0.45% P. C-DDGS = corn distillers dried grains with solubles. Provided the following per kilogram in the basal diet: Cu (as CuSO4), 16.5 mg; Fe (as FeSO4), 165 mg; I [as Ca(IO3)2], 0.3 mg; Mn (as MnSO4), 39 mg; Zn (as ZnSO4), 165 mg; and Se (Na2SeO3), 0.3 mg. 3 Provided the following per kilogram in the basal diet: vitamin A, 6,125 IU; vitamin D3, 700 IU; vitamin E, 50 IU; vitamin K, 30 mg; vitamin B12, 0.05 mg; riboflavin, 11 mg; niacin, 56 mg; and pantothenic acid, 27 mg. 4 TiO2 recovered was 0.53, 0.30, 0.33, 0.31, 0.31, 0.30, and 0.30%, respectively. 1 2

490 above as well as by others (Robinson et al., 2008; Dahlen et al., 2011; Jacela et al., 2011; Liu, 2011; Liu et al., 2012) but are not discussed in this paper. The extensive chemical composition data for the C-DDGS sources evaluated in the current study are provided because these data are often lacking in the literature (NRC, 2012) and may be useful as a reference to understand research responses related to effects of feeding C-DDGS on pork fat quality (McClelland et al., 2012) and research related to lipid peroxidation (Liu et al., 2014). Lipid free fatty acids, lipid peroxidation, and mycotoxin concentrations (Table 2) suggest that the C-DDGS samples obtained were of high quality and are similar to our previous work (Kerr et al., 2013; Song and Shurson, 2013), suggesting that the dry-grind ethanol plants that were chosen as suppliers of C-DDGS samples have high-quality processing methods. In contrast to our previous work (Anderson et al., 2012; Kerr et al., 2013) a corn–soybean meal basal diet was used instead of a corn-only basal diet. This decision was based on the fact that the same basal diet and the basal plus C-DDGS diets would be fed to pigs over a longer time period during Exp. 2, which is unlike the relatively short feeding period when conducting typical nutrient and energy balance experiments. It was hypothesized that a corn-only basal diet might bias the results, a bias that would likely have the greatest effect on NE, intermediate effect on ME, and least effect on DE (Anderson et al., 2012). The dietary inclusion level of C-DDGS was also increased to 40% instead of 30%, which was used in our previous studies (Anderson et al., 2012; Kerr et al., 2013) to increase the likelihood of observing differences in DE, ME, or NE content among the C-DDGS samples used in these experiments, except for the C-DDGS source B, which was included at 30% due to limited quantity of sample available. A 40% inclusion rate was used because this would represent the upper level of C-DDGS used in commercial swine growing-finishing

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diets in the industry and would have minimal effects on feed intake (Stein and Shurson, 2009).

Exp. 1—DE and ME Content of C-DDGS Averaged across all treatments, including pigs fed the basal diet, pig BW (87.0, 103.9, and 98.3 kg) and ADFI (2,432, 2,560, and 2,334 g/d) were different (P < 0.01) among the 3 groups of pigs used (group 1, 2, and 3, respectively). Similarly, pigs in feeding period 1 were lighter than pigs in feeding period 2 (91.1 vs. 101.7 kg, respectively; P < 0.01), with total ADFI being similar between feeding period 1 and feeding period 2 (2,425 vs. 2,459 g/d, respectively; P = 0.28). These differences were expected because of the variation in the pig population available at the research farm, and because pig group (1, 2, and 3) and feeding period (1 and 2) were clearly defined time periods. Consequently, pig group and feeding period remained as blocking variables in the statistical model for all parameters measured. Overall, no differences were observed for BW or ADFI among pigs fed the basal diet or pigs fed the various C-DDGS diets (Table 4). Comparisons of DE and ME content of C-DDGS samples with other published reports are useful for database building. The 2012 Nutrient Requirements of Swine (NRC, 2012) contains energy and nutrient composition tables for low (6% and 10% EE) oil C-DDGS. However, caution should be used when considering the use of the low- and medium-oil DDGS energy and nutrient values in practical diet formulations because they were obtained from a small number (n = 0 to 13) of C-DDGS sources in published studies, especially for DE and ME content (n = 0 to 2). There are more than 200 ethanol plants in the United States, and energy and nutrients among these sources are highly variable (Stein and Shurson, 2009; Kerr et al., 2013). Furthermore, the concentration of nutrients does not increase in direct proportion to the

extent of oil extraction in a predictable manner (Kerr et al., 2013). In the current study, C-DDGS samples (Table 4) had an average DE and ME content of 3,931 and 3,793 kcal/kg of DM, respectively, which were higher than our previous data (3,650 and 3,345 kcal/kg of DM, respectively; Kerr et al., 2013). These DE and ME differences may be due to the use of a corn–soybean meal basal diet in the current experiment (3,750 and 3,683 kcal/kg of DM, respectively) compared with using a corn basal diet (3,563 and 3,489 kcal/kg, respectively) in our last experiment (Kerr et al., 2013), such that the type of basal diet used in these determinations may bias the energy values determined for the test ingredients. Furthermore, differences in energy determinations between experiments are not unexpected given that BW (Le Goff et al., 2002), particle size (Yanez et al., 2011), basal diet (Li et al., 2014), feed intake (Chastanet et al., 2007), and laboratory variation (Cromwell et al., 2000) may all affect the energy concentration determined for a diet. Development and use of prediction equations are not new concepts, but often these equations are based on total composition of the diet (Just et al., 1984; Noblet and Perez, 1993; Bulang and Rodehutscord, 2009) and not a specific ingredient. Our approach has been to develop prediction equations based on the composition of specific feedstuffs (Anderson et al., 2012; Kerr et al., 2013) to improve accuracy and reduce prediction error and bias. In Exp. 1, no physical or chemical measurement was significant at P ≤ 0.15 to predict DE or ME content of C-DDGS. Because DE or ME could not be predicted using any physical or chemical measures, prediction of DE or ME as a percentage of GE or ME as a percentage of DE was not attempted, similar to that reported in our previous research (Kerr et al., 2013). The inability of these physical and chemical composition measurements to predict DE or ME was surprising because it was expected that the relatively large differences in several variables among the C-

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Table 4. Energy content and digestibility coefficients of pigs fed the basal diet or C-DDGS, DM basis, Exp. 1 C-DDGS source Item Observations BW, kg ADFI, g Energy content GE, kcal/kg DE, kcal/kg ME, kcal/kg DE:GE ME:DE ME:GE Digestibility, % ADF Carbon DM Ether extract Nitrogen NDF Phosphorus Sulfur

Statistics2

Basal1

A

B

C

D

E

F

68 96.1 2,464   4,267 3,750 3,683 87.88 98.19 86.32   65.03 88.78 88.00 22.87 89.29 47.77 40.86 80.89

12 97.3 2,379   5,227 3,974 3,830 76.03 96.37 73.27   76.08 76.14 74.33 59.82 84.60 60.88 54.78 85.34

8 96.6 2,419   5,094 3,842 3,723 75.42 96.78 73.09   73.28 75.31 72.47 55.85 84.47 53.46 63.28 82.14

12 97.2 2,459   5,052 4,017 3,874 79.51 97.58 76.68   76.90 78.20 76.09 46.32 86.45 58.52 50.69 87.64

12 96.2 2,474   4,981 3,836 3,716 77.02 96.85 74.60   55.44 75.91 72.52 75.95 83.61 41.66 51.19 88.85

12 94.8 2,376   4,918 3,874 3,734 78.77 96.45 75.93   55.16 78.12 74.77 73.47 85.89 44.83 50.45 88.84

12 97.2 2,434   5,155 4,038 3,893 78.33 96.43 75.52   61.30 77.67 74.84 81.25 84.70 46.04 44.27 89.01

SD

P-value

— 4.6 164

— 0.76 0.61

— 219 220 4.37 2.07 4.38   5.78 4.60 5.34 7.75 3.64 8.89 9.39 2.77

— 0.12 0.21 0.26 0.75 0.36   0.01 0.58 0.59 0.01 0.46 0.01 0.01 0.01

Apparent total-tract digestibility and DE and ME of the corn–soybean meal basal diet for each pig, which was used as its own control in the determination of the digestibility and energy values for each corn distillers dried grains with solubles (C-DDGS) source. 2 Statistics apply to the C-DDGS sources only and do not include pigs fed the basal diet. 1

DDGS samples would have been great enough to develop regression equations among these 6 C-DDGS sources. However, in one experiment involving 4 C-DDGS sources from our past research (Kerr et al., 2013), predictive equations could not be generated from chemical composition analysis. Similar challenges in generating predictive equations have been reported in the evaluation of meat and bone meal (Adedokun and Adeola, 2005; Olukosi and Adeola, 2009). This supports our inability to generate an equation in the current experiment, suggesting that to generate prediction equations, a wider range in chemical composition than used in this experiment is necessary (Rochell et al., 2011; Anderson et al., 2012; Kerr et al., 2013; Meloche et al., 2013, 2014). In an effort to validate past prediction equations generated in our laboratory (Anderson et al., 2012; Kerr et al., 2013) and a recent literature review (Urriola et al., 2014), the bestfit DE and ME equations from each of these sources was used to predict the

DE and ME relative to the actual DE and ME values determined in Exp. 1. A summary of this analysis is shown in Table 5 and indicates that DE and ME equations suggested by Anderson et al. (2012) and Kerr et al. (2013) both underestimated the actual DE and ME content determined in the current trial. Some of this difference between predicted and actual could be due to experimental bias because the average DE and ME content of the corn–soybean meal basal diet in the current experiment averaged 191 kcal/ kg of DM higher that that determined for the corn basal diet determined in the experiments by Kerr et al. (2013). This difference could potentially account for the average DE and ME prediction difference of 241 kcal/kg of DM as shown in Table 5. This is not the case, however, for the DE and ME differences of 200 kcal/kg of DM using equations reported by Anderson et al. (2012) and the values determined in the current trial, where the corn DE and ME values (3,883 and 3,805 kcal/ kg of DM, respectively) reported by

Anderson et al. (2012) were greater than the DE and ME for the corn– soybean meal basal diet (3,750 and 3,683 kcal/kg of DM, respectively). The larger differences between the actual determined values and the values predicted by Urriola et al. (2014) may also be exacerbated due to differences in BW, particle size, type of basal diets, ADFI, and laboratory variation between experiments, as previously described. Some of the major challenges in conducting any experiment are controlling errors associated with laboratory analysis, collection practices, and animal-to-animal variation. In an attempt to minimize these sources of error, a single laboratory and analytical procedures for diet and ingredient analysis has been used. Our previous research has shown that laboratoryto-laboratory variation alone can account for a 10% error in predicting the caloric value for C-DDGS (data not shown). A consistent protocol for fecal and urine sample collection methods and preparation (Lammers

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et al., 2008; Kerr et al., 2009; Anderson et al., 2012; Kerr et al., 2013) was also used, even though fecal and urine sample collection methods have been shown to have little to no effect on subsequent energy values determined using the difference procedure (Li et al., 2014). Realizing the potential for animal-to-animal variation in nutrition research, each pig was used as its own control as suggested by Jacobs et al. (2013). Relatively little variation (as indicated by relatively low CV) for DE and ME content, as well as for carbon, DM, N, and S digestibility, was noted for all pigs fed the basal diet (Table 6). Part of this is due to the large mean value, and thus, the variation is lost when a large denominator is used in the calculation. Additionally, the low CV for these measures may also be due to the low inherent variability of the quantitative

methods used for determining energy (bomb calorimeter), and for carbon, N, and S (thermo combustion). Dry matter is a qualitative measure because it is not measured against a standard, has a large denominator, and is a fairly standard assay resulting in generally low CV. In contrast, ADF and NDF (filter-bag technique) and EE (solvent extraction) are more qualitative measures because fiber and lipids are a collection of chemically similar but complex compounds. These methods measure more than just one compound, and there are no standards used in these methods. In addition, fiber analysis often involves the use of enzymes or detergents, and lipid analysis uses various solvents that have different extraction efficiencies. The variation noted in phosphorus digestibility (17.9% CV) is a bit perplexing given that the methodol-

ogy is an acid digestion process and known standards are used. However, it is important to realize that errors can be additive, and even though our laboratory maintains a CV of 5% or less for internal laboratory analysis, these are included on the overall CV listed in Table 6. Apparent total-tract digestibility of ADF, carbon, DM, EE, N, NDF, phosphorus, and S for C-DDGS in the current experiment (Table 4) compare favorably to our previous data (Kerr et al., 2013). The carbon, DM, EE, N, and S digestibilities were greater but ADF, NDF, and phosphorus digestibilities were lower in the current experiment compared with those reported by Kerr et al. (2013). Use of apparent total-tract digestibility coefficients to predict DE and ME has been done by others (Noblet and Perez, 1993) but was beyond the scope

Table 5. Predicted energy values of C-DDGS1 used in Exp. 1 based on published prediction equations, DM basis Equation 12 Item C-DDGS A B C D E F Mean

Equation 23

DE, actual

Predicted

Difference

3,974 3,842 4,017 3,836 3,874 4,038

3,813 3,738 3,744 3,651 3,593 3,768

−161 −104 −273 −185 −281 −270 −212

Equation 42 C-DDGS A B C D E F Mean

Equation 34

Predicted

Difference

3,898 3,801 3,799 3,682 3,619 3,816

−76 −41 −218 −154 −255 −222 −161

Equation 53

ME, actual

Predicted

Difference

3,830 3,723 3,874 3,716 3,734 3,893

3,762 3,638 3,615 3,512 3,444 3,678

−68 −85 −259 −204 −290 −215 −187

Predicted

Difference

3,655 3,610 3,593 3,734 3,688 3,867

−319 −232 −424 −102 −186 −171 −239

Equation 64

Predicted

Difference

3,679 3,518 3,476 3,354 3,280 3,545

−151 −205 −398 −362 −454 −348 −320

Predicted

Difference

5,021 4,878 4,847 4,763 4,691 4,928

1,191 1,155 973 1,047 957 1,035 1,060

C-DDGS = corn distillers dried grains with solubles source. Energy values (GE, DE, and ME) are expressed on a kilocalories per kilogram basis; ether extract (EE), NDF, CP, and TDF are expressed on a percentage basis. 2 Anderson et al. (2012) Equation 1: DE = −1,358 + (1.26 × GE) − (30.91 × TDF) − (33.14 × EE), Equation 4: ME = (0.90 × GE) − (29.95 × TDF). 3 Kerr et al. (2013) Equation 2: DE = 2,084 + (0.67 × GE) − (53.65 × %TDF), Equation 5: ME = 4,558 − (50.08 × %TDF) + (52.26 × %EE). 4 Urriola et al. (2014) Equation 3: DE = −2,161 + (1.39 × GE) − (20.7 × NDF) − (49.3 × EE), Equation 6: ME = −261 + (1.05 × GE) − (7.89 × CP) + (2.47 × NDF) − (4.99 × EE). 1


Table 6. Variation in energy and chemical composition digestibility coefficients in pigs fed the basal diet, Exp. 11 Criterion Energy, kcal/kg of DM DE ME Digestibility, % ADF Carbon DM Ether extract Nitrogen NDF Phosphorus Sulfur 1

Mean

SD

CV

Minimum

Maximum

3,750 3,683   65.03 88.78 88.00 22.87 89.29 47.77 40.86 80.89

65.6 60.0   6.07 1.34 1.48 7.55 1.26 9.93 7.32 1.66

1.75 1.63   9.33 1.51 1.68 33.01 1.41 20.79 17.91 2.05

3,611 3,544   52.99 85.87 85.15 10.59 85.32 28.93 27.89 76.81

3,883 3,817   76.56 91.97 90.99 38.90 92.00 65.82 54.84 85.03

Data represent 68 pigs fed the corn–soybean meal basal diet.

and aim of this study. The digestibility of phosphorus is a measure of high interest due to the cost of phosphorus in dietary formulations. The average apparent total-tract digestibility of phosphorus of C-DDGS in the current experiment (51.8%) compares favorably to the 50.8, 55.5, 56.0, and 59.3% reported by others (Pedersen et al., 2007; Widyaratne and Zijlstra, 2007; Stein et al., 2009; Kerr et al., 2013, respectively) but is less than the 68.6% reported by Almeida and Stein (2010).

Exp. 2—NE Chemical analysis has long been the standard for measuring body composition in pigs but is time consuming, expensive, destructive, and not without error. A reliable, convenient, and nondestructive method

for determining total lean, lipid, and bone composition is the use of DXA, which has been shown to have greater accuracy than many routinely used methods (Suster et al., 2003, 2004). Furthermore, using the actual initial body composition of each individual animal in the calculation of body lean, lipid, and bone mineral content should improve the accuracy of tissue gain assessment. For the 79 gilts used in Exp. 2, initial bone, lipid, and lean composition averaged 1.30, 17.18, and 81.52%, respectively (Table 7). More importantly, the range in initial body composition of bone, lipid, and lean was 0.54, 5.63, and 5.95 percentage units, respectively. Thus, like that suggested for Exp. 1, it was postulated that using the pig as their own control would be crucial in controlling and reducing animal-to-animal variation. This is especially important

Table 7. Variation in the initial body composition of pigs used in Exp. 2 Criterion1

Mean

SD

CV

Minimum

Maximum

BW, kg Bone mineral content, % Lipid, % Lean, % Protein, %

45.35 1.30 17.18 81.52 18.16

4.08 0.13 1.11 1.19 0.26

9.00 10.00 6.46 1.44 1.46

34.50 0.97 14.65 78.24 17.42

57.00 1.51 20.28 84.19 18.75

1

Represents 79 pigs at the initiation of the trial.

493

when ranges in pig BW are used in experiments, which in this experiment, ranged from 34.5 to 57.0 kg. To calculate whole body energy based on body composition, the daily NEm for each pig was calculated as 179 kcal/kg of BW0.60·d−1 (Noblet et al., 1994), with protein assumed to contain 5.54 kcal/g and lipid assumed to contain 9.34 kcal/g (Birkett and DeLange, 2001). These values are well defined and largely accepted in the literature (de Lange et al., 2012; NRC, 2012). The DXA used in the current experiment provided outputs that included whole body bone, lipid, and lean content values, but to determine energy retained, the conversion of lean to protein was required. Prior to the current experiment, calibration of DXA outputs to whole body proximate analysis was conducted at Iowa State University. Briefly, 45 pigs (5 to 100 kg of BW) were scanned by DXA and euthanized; gastrointestinal and bladder contents were stripped; and each whole pig was ground and analyzed for lipid, water, protein, and ash. Thereafter, whole body composition was calculated and regressed against the DXA-predicted results. The results of this calibration allowed for the calculation of protein from lean mass. Differences in ADG (P ≤ 0.10) and G:F (P < 0.05), daily bone and lipid accretion (P ≤ 0.01), and daily GE retained (P < 0.05) were observed among pigs fed the different C-DDGS sources, Table 8. In contrast, there were no differences noted in the determined NE content among the C-DDGS sources. On average, the NE of the 6 C-DDGS was 2,207 kcal/kg of DM (Table 8), which is lower than the 2,622 kcal NE/kg of DM reported by the NRC (2012) for C-DDGS containing 6 to 9% EE but is similar to the 2,266 kcal/kg of DM reported by Gutierrez et al. (2014). Given the lack of NE differences among sources in the current experiments, it was not surprising that no physical or chemical measurement was significant at P ≤ 0.15 to predict NE content of C-DDGS. Because NE could not be predicted, prediction of NE as a

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percentage of GE, DE, or ME was not attempted. The inability to generate a prediction equation for NE supports our overall suggestion that to generate robust energy-prediction equations, a wider range in nutrient and energy composition of the test diets or ingredients than used in this experiment is necessary. This is supported by the pioneering work of Noblet and Perez (1993) and Noblet et al. (1994), where diets were formulated to contain a range of energy levels and chemical composition wide enough to generate prediction equations for DE, ME, and NE based on chemical composition. In addition to the body composition data, a fresh fecal sample was obtained on d 31 to determine dietary

DE content using an indirect marker to compare this value to the dietary DE determined in Exp. 1 by total collection. As supported by others (Kavanagh et al., 2001; Agudelo et al., 2010), differences were noted between the dietary DE values determined indirectly by marker methodology (Exp. 2, Table 8) and total collection (Exp. 1, Table 4). This was not unexpected because pigs, methods, and analytical methods differed between these 2 experiments. However, one might expect that the differences would be relatively consistent between experiments, but they were not. The difference ranged from being 311 kcal/kg of DM greater for pigs fed the basal plus C-DDGS source B compared

with being 270 kcal/kg of DM lower for pigs fed the basal diet between the use of the marker method versus the total collection method, respectively. These results confirm the challenges in conducting digestibility trials.

IMPLICATIONS Data from the experiments described herein indicate that reducedoil C-DDGS are a good source of DE and ME for swine but have a relatively lower NE content. This lower NE content of C-DDGS is likely due to their higher fiber content and the insoluble nature of fiber, as well as reduced lipid digestibility and contribution to NE content. These ex-

Table 8. Energy content of basal and C-DDGS, Exp. 21 C-DDGS source Item Observations C-DDGS, % ADG, g ADFI, g G:F, g/kg Whole body accretion Bone content gain, g/d Lipid gain, g/d Lean gain, g/d Protein gain, g/d GE intake, kcal/d GE retained, kcal/d Average BW,3 kg NE,4 kcal/kg of DM NE:GE5 NE:DE5 NE:ME5 DE,6 kcal/kg of DM Indirect marker Total collection

Statistics2

Basal

A

B

C

D

E

F

13 — 910 2,060 443 9.9 146.1 703.8 153.3 7,783 4,329 61.4 2,370 55.6 63.2 64.4 3,480 3,750

14 40 845 2,021 419 6.6 141.3 621.8 135.5 8,415 4,150 59.7 2,228 42.6 56.1 58.2 4,050 3,974

7 30 886 2,033 436 8.3 153.6 647.7 141.1 8,177 4,300 59.8 2,193 43.0 57.1 58.9 4,153 3,842

8 40 828 2,024 409 6.8 133.2 615.0 134.0 8,286 4,091 60.9 2,151 42.6 53.5 55.5 3,880 4,017

11 40 786 2,045 386 5.2 120.3 582.3 126.9 8,347 3,891 59.0 2,107 42.3 54.9 56.7 3,885 3,836

14 40 787 1,981 396 4.9 128.1 597.7 130.2 8,010 3,988 59.2 2,255 45.9 58.2 60.4 3,859 3,874

12 40 852 1,984 429 5.5 143.9 631.3 137.5 8,256 4,172 59.1 2,310 44.8 57.2 59.3 4,108 4,038

SD

P-value

— — 96 147 39 1.3 22.2 66.5 14.5 602 312 4.77 196 3.9 5.0 5.2 276 246

— — 0.10 0.82 0.02 0.01 0.01 0.22 0.22 0.56 0.04 0.94 0.21 0.18 0.37 0.34 0.07 0.18

Initial BW averaged 45.3 kg (SD = 4.1 kg), containing 1.30% bone (SD = 0.13), 17.18% lipid (SD = 1.11%), and 81.52% lean (SD 1.19%). The trial period was 35 d. Final BW averaged 74.3 kg (SE = 5.5 kg). Gain of bone, fat, and lean obtained by dual energy x-ray absorptiometry. Performance, body tissue gain, and energy intake and retention based on total diet consumption. C-DDGS = corn distillers dried grains with solubles. 2 Statistics are relative only to the C-DDGS sources and do not include pigs fed the basal diet. 3 Average BW used for determination of maintenance energy needs, calculated as 179 kcal/kg of BW0.60·d−1. 4 Data represent the complete basal diet or the specific corn-DDGS source. Energy retention data were based on the following assumptions: lipid = 9.34 kcal/g, protein = 5.54 kcal/g, and bone = 0 kcal/g. 5 Energy values (GE, DE, and ME) were obtained from Exp. 1, Table 4. 6 Data were obtained from indirect marker methodology for pigs fed in Exp. 2 and total collection from pigs fed the same diets described in Exp. 1, Table 4. 1


periments also indicate that a lack of ingredient variation when conducting these types of experiments makes it difficult to generate energy-prediction equations based on their chemical composition. Last, variation associated with energy and nutrient digestion trials make research difficult but should not preclude the effort to conduct research to generate predictive equations that can be used to rapidly and accurately estimate energy and nutrient value for use in feed formulations.

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