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ANIMAL NUTRITION |
* Department of Animal Sciences, University of Illinois, Urbana 61801;
and
Danisco Animal Nutrition, SN8 1AA Marlborough, Wiltshire, UK; and
Evonik Degussa Corp., Kennesaw, GA 30144
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Abstract |
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 Top Abstract INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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Key Words: amino acid • digestibility • distillers dried grains • distillers dried grains with solubles • distillers solubles • pig
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INTRODUCTION |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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), which is blended with the condensed solubles (syrup) during drying. If the coarse grain fraction of the whole stillage is dried without the solubles added to it, the product is called distillers dried grains (DDG).
Results of previous research indicate that the digestibility of AA in DDGS may vary according to the location of the plant that produced it (Whitney et al., 2000; Fastinger and Mahan, 2006). However, the DDGS used in these studies were sourced from ethanol plants located only in the upper Midwest, and there are no data on the AA digestibility in DDGS sourced from the entire Midwestern region.
The quantity of solubles that is added to the DDG may also contribute to variability in the composition of DDGS (Goodson and Fontaine, 2004), but the digestibility of AA in DDG and DDGS has not been compared. Likewise, the digestibility of AA in DDGS produced in a dry grind ethanol plant (DDGSethanol) has not been compared with the digestibility of AA in DDGS produced at a modern beverage plant (DDGSbeverage).
Thus, the objective of the present work was to compare the digestibility of AA in DDGS sourced from ethanol plants located in the northern (i.e., MN), central (i.e., IL), or southern (i.e., KY) corn-producing area in the United States. The second objective was to compare the AA digestibility of DDG and DDGS. The third objective was to compare the AA digestibility of DDGS produced from 2 types of alcohol extraction facilities (i.e., dry grind ethanol plants and alcoholic beverage plants).
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MATERIALS AND METHODS |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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Animals, Housing, and Experimental Design
In Exp. 1, twelve barrows (initial BW: 37.0 ± 5.6 kg) were allotted to a replicated 4 x 6 Youden square design (Anderson and McLean, 1974) with 4 periods and 6 diets. In Exp. 2, nine barrows (initial BW: 76.0 ± 9.2 kg) were used in a 7 x 9 Youden square design with 7 periods and 9 diets. All barrows were the offspring of SP-1 boars that were mated to Line 13 sows (Ausgene Intl. Inc., Gridley, IL), and they were surgically fitted with a T-cannula in the distal ileum (Stein et al., 1998). Pigs were housed in an environmentally controlled room (22°C) with fully slatted pens (1.2 x 1.8 m). A feeder and a nipple drinker were installed in each pen.
Diets, Feeding, and Sample Collection
In Exp. 1, five sources of corn DDGS from dry grind fuel ethanol plants were used (Table 1). Two of the DDGS samples were from Minnesota (MN1, MN2), 2 were from Illinois (IL1, IL2), and 1 sample was from Kentucky (KY). All samples were collected from different ethanol plants. Five diets based on each of the 5 DDGS sources and a N-free diet were formulated (Tables 2 and 3). In Exp. 2, one sample of DDG, 1 sample of DDGSbeverage, and 6 samples of DDGSethanol were used (Table 4). Eight diets based on each of the co-products and a N-free diet were formulated (Tables 2 and 5). The DDG was from Minnesota, the DDGSbeverage was sourced from Kentucky, and the 6 samples of DDGSethanol that were used in Exp. 2 were sourced from Illinois (2 samples), Indiana, Wisconsin, North Dakota, and Minnesota. Samples of each source of DDG and DDGS were collected on arrival and stored at 4°C until analyzed.
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). The daily feed allowance was divided into 2 equal meals that were fed at 0800 and 1700 h.
The initial 5 d of each period were considered an adaptation period to the diet, and ileal digesta were collected on d 6 and 7 of each period as described previously (Stein et al., 2006). All collected digesta were stored at –20°C, and all samples were lyophilized and ground before chemical analyses.
Chemical Analyses
Samples of ingredients, diets, and ileal digesta were analyzed for DM (procedure 4.1.06; AOAC, 2000), CP, and AA at Degussa Analytical Nutrition Laboratory in Hanau, Germany. Amino acids were analyzed by cation exchange chromatography (method 994.12; AOAC, 1995). Analysis for Met and Cys were performed by initially oxidizing the samples with performic acid (Llames and Fontaine, 1994). Tryptophan was analyzed after hydrolysis in 4 M barium hydroxide at 110°C for 20 h (Llames and Fontaine, 1994). Tyrosine was not analyzed. Diets were also analyzed for Ca (procedure 4.8.03; AOAC, 2000) and P (procedure 3.4.11; AOAC, 2000), and all ingredients were analyzed for ADF and NDF (procedure 4.6.03; AOAC, 2000) and starch (Xiong et al., 1990). All samples of diets and ileal digesta were analyzed for Cr (procedure 9.2.39; AOAC, 2000) after nitric acid-perchloric acid wet ash sample preparation.
Calculations and Statistical Analysis
The apparent ileal digestibilities (AID), basal ileal endogenous losses, and standardized ileal digestibilities (SID) of CP and AA were calculated for DDG and each source of DDGS as described by Stein et al. (2006). Data were analyzed by ANOVA using the MIXED procedure (SAS Inst. Inc., Cary, NC). The pig was the experimental unit. Pig and period were considered random effects, and diet was the fixed effect. Least squares means were calculated and separated using the PDIFF option of SAS. In Exp. 1, the CONTRAST option of SAS was used to compare data from DDGS sourced from different regions. The CONTRAST option was also used in Exp. 2 to compare data for DDG and DDGS and to compare data for DDGSbeverage and DDGSethanol. In all analyses, a probability of P < 0.05 was considered significant.
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RESULTS |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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The AID of CP and all AA except Arg, Lys, Leu, and Trp were similar among the 5 sources of DDGS (Table 6). The mean AID for Lys was 63.1% and ranged from 60.3 to 67.4%. The AID of Lys was greater (P < 0.05) in DDGS from MN2 than in DDGS from MN1, IL1, and KY but not different from IL2. The DDGS from Minnesota had a greater AID for Arg (P < 0.05) and Lys (P < 0.05) than DDGS from Kentucky, whereas DDGS from Illinois had a greater (P < 0.01) AID for Leu compared with DDGS from MN.
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). The mean SID of Lys was 68.5%, and the SID of Lys was greater (P < 0.05) for DDGS from MN2 than from MN1, IL1, and KY but not different from IL2. The DDGS from Illinois had a greater (P < 0.01) SID for Leu than the DDGS from Minnesota, whereas the DDGS from Kentucky had a greater (P < 0.05) SID of Arg and Leu compared with DDGS from Minnesota. However, DDGS from Minnesota had a greater (P < 0.05) SID of Lys than DDGS from Kentucky, but there was no influence of region on the SID of other AA.
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The mean CP, NDF, ADF, and starch concentration in the 6 DDGSethanol sources were 25.54, 29.13, 11.61, and 8.55%, respectively (Table 4
). The CP, NDF, ADF, and starch concentration in DDGSbeverage were 25.55, 31.67, 11.64, and 7.32%, respectively, and these values were within the range of values observed in DDG-Sethanol. The concentration of CP, NDF, ADF, and starch in DDG were 28.77, 37.29, 18.19, and 3.83%, respectively. These values were greater than in DDGSethanol and DDGSbeverage. However, the concentration of starch was lower in DDG compared with both types of DDGS.
The AID for CP and all AA varied (P < 0.01) among the 6 sources of DDGSethanol (Table 8). Sources 3 and 5 had a greater (P < 0.01) AID for Lys (69.3 and 70.0%, respectively) than sources 1, 2, 4, and 6 (51.1, 44.4. 58.9, 60.1%, respectively).
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The mean SID for Lys in DDGSethanol was 64.8% (Table 9), but DDGS sources 3 and 5 had a greater (P < 0.01) SID for Lys (73.8 and 74.5%, respectively) compared with sources 1, 2, 4, and 6 (56.8, 51.4, 63.7, and 68.7%, respectively). Likewise, the SID for CP and all other AA varied (P < 0.05) among the 6 sources of DDGSethanol.
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DISCUSSION |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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The nutrient composition and the AID and SID of CP and AA in the 5 sources of DDGS that were used in Exp. 1 were similar to previously reported values (Fastinger and Mahan, 2006; Stein et al., 2006). The differences in the SID of Lys, Leu, and Glu among the 5 DDGS sources as well as the differences in the SID for Lys, Leu, and Arg between Illinois, Minnesota, and Kentucky indicate that both interplant variation and interregion variation in DDGS AA digestibility exist. However, the differences were not consistent and only limited to Lys, Leu, and Arg digestibility. The differences may be due to plant design, processing procedures, and corn-growing conditions that can affect the starch concentration of corn (Mathew et al., 1999). The variability in digestibility of AA that was obtained in this experiment was lower than what has been previously reported (Fastinger and Mahan, 2006; Stein et al., 2006). All 5 sources of DDGS used in this experiment had SID values for AA that were close to average values obtained in previous experiments. However, the results of this experiment do not indicate that DDGS from one region is better than DDGS from another region, and it is concluded that the region in which DDGS is produced is not a major contributor to the variability in nutrient concentration and AA digestibility.
Composition of DDG, DDGSethanol, and DDGSbeverage
The concentrations of CP and AA in DDGSethanol and DDGSbeverage were similar to reported values (Cromwell et al., 1993; Fastinger and Mahan, 2006; Stein et al., 2006), but the CP and AA concentration of DDG was greater than the values reported by NRC (1998). The concentration of CP in the solubles is approximately 16.8% (Larson et al., 1993), whereas the concentration of CP in DDG was 28.77% (as-fed basis). The greater CP concentration in DDG than in DDGSethanol and DDGSbeverage may, therefore, be a result of the lower CP concentration in distillers solubles than in DDG. This observation concurs with data showing that the concentration of AA in distillers solubles produced from barley is at least 50% lower than in DDG produced from barley (Näsi, 1985).
The concentration of NDF in DDGSethanol and in DDGSbeverage was lower than previously reported (NRC, 1998; Fastinger and Mahan, 2006; Stein et al., 2006). This may be a result of the use of more effective enzymes during fermentation, because the use of enzymes may reduce the NDF concentration in DDGS (Näsi, 1985). The ADF and starch concentration of both DDGS sources were within the range of values that have been reported (Belyea et al., 2004; Stein et al., 2006).
Ileal AA Digestibility in DDGSethanol and DDGSbeverage
The AID and SID of CP and AA in DDGS were within the range of previously reported values (Fastinger and Mahan, 2006; Stein et al., 2006). However, the SID of most AA in DDGS obtained in the present experiments is greater than the values reported for true ileal AA digestibility of DDGS (NRC, 1998).
The concentration and the SID of most AA in DDGSethanol were not different from the values in DDGSbeverage, which indicates that the SID of AA in DDGS is not affected by the type of facility that is used in the production of DDGS. The exception, however, was the SID of Lys, which was greater in DDGSbeverage than in DDGSethanol. This observation indicates that the DDGSbeverage used in this experiment may have been less heat-damaged than the sources of DDGSethanol that were used. Although it has been suggested that AA in DDGS produced in plants built before 1990 are less digestible than in DDGS produced in newer plants, the present results indicate that the difference is not related to whether the DDGS originates from an ethanol plant or a beverage plant. The DDGSbeverage that was used in this experiment was sourced from a bourbon plant. In the production of bourbon, 70% of the grain is corn, 15% is rye, and 15% is malted barley (Ralph, 2003), whereas only corn was used in the production of the DDGSethanol that was used in this experiment. The results of the experiment, however, indicate that the inclusion of malted barley and rye at the concentrations used to produce bourbon does not significantly change the composition or the digestibility of AA in the resulting DDGS compared with DDGS produced from fuel ethanol production.
Ileal AA Digestibility in DDG
The greater SID of CP and AA in DDG than in DDG-Sethanol is most likely caused by a greater AA digestibility in the whole stillage than in the solubles. This observation concurs with Näsi (1985), who reported that the AID for CP was lower in solubles than in DDG. The digestibility of Lys and Met by cecectomized turkeys in distillers solubles was only 51 and 21%, respectively (Belyea et al., 1998), which also indicates that the digestibility in solubles is low. A contributing factor to the greater digestibility values in DDG than in DDGS may be that less heat is required to dry the DDG if solubles are not added to the stillage. Therefore, the risk of reducing AA digestibility due to heat damage is reduced in DDG compared with DDGS.
In conclusion, results from these 2 experiments indicate that the variability in digestibility of AA among sources of DDGS that have been reported in several experiments is not caused by the region in which the DDGS is produced. Likewise, AA digestibility is similar for DDGS produced by an ethanol plant and by a beverage plant. However, for most AA, the digestibility is greater in DDG than in DDGS. The present data also confirm that the variability of the digestibility of Lys is greater than the variability of the digestibility of other AA, which indicates that heat damage may be a major contributing factor to variability in Lys digestibility. The digestibility of AA in most sources of DDGS is greater than the digestibility of AA reported by NRC (1998).
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Footnotes |
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2 Corresponding author: hstein{at}uiuc.edu
Received for publication January 13, 2008. Accepted for publication May 7, 2008.
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LITERATURE CITED |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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