TY - JOUR
AU1 - May, M. L.
AU2 - DeClerck, J. C.
AU3 - Leibovich, J.
AU4 - Quinn, M. J.
AU5 - DiLorenzo, N.
AU6 - Smith, D. R.
AU7 - Hales, K. E.
AU8 - Galyean, M. L.
AB - ABSTRACT The effects of wet distillers grains with solubles (WDG) on in vitro rate of gas production, IVDMD, H2S production, and VFA were evaluated. Five substrate treatments that were balanced for ether extract content were arranged in a 2 × 2 + 1 factorial. Factors were concentration (15 or 30%; DM basis) and source of WDG (corn or sorghum WDG; CDG and SDG, respectively) plus a 0% WDG control in substrates with steam-flaked corn as the basal grain. Control substrates had greater (P < 0.01) IVDMD and total gas production per gram of substrate DM than WDG-based substrates, and IVDMD was greater (P = 0.03) for CDG than for SDG substrates. Increasing WDG inclusion from 15 to 30% decreased IVDMD and total gas production (P < 0.05), but H2S production (μmol/g of fermentable DM) increased (P = 0.01) as inclusion of WDG increased. There were no differences (P ≥ 0.10) among treatments in proportions of major VFA, acetate:propionate ratio, and total VFA concentration. These results suggest that including WDG in the substrate decreased IVDMD and gas production, which was particularly evident as WDG increased from 15 to 30% of substrate DM. In addition, CDG seemed to be more digestible than SDG. Hydrogen sulfide production increased with increasing WDG in the substrate, reflecting greater S concentrations in WDG, but in vitro VFA profiles were not affected by WDG concentration or source. INTRODUCTION Expansion of the ethanol industry has increased the use of wet distillers grains with solubles (WDG) in beef cattle finishing diets. Because fiber, protein, and ether extract are concentrated approximately 3-fold when starch is fermented to produce ethanol (Klopfenstein et al., 2008), WDG typically replaces portions of the grain and supplemental protein in feedlot diets. At present, limited research has been published with WDG in steam-flaked corn (SFC)-based diets. Depenbusch et al. (2009) evaluated both wet and dry corn and sorghum distillers grains at 15% of the dietary DM in SFC-based diets and observed no effects on ADG, DMI, or G:F. In a companion study to the present experiment, May et al. (2010) conducted 2 experiments to evaluate corn WDG (CDG) and sorghum WDG (SDG) in feedlot diets. Decreased carcass-adjusted final BW, HCW, and G:F were noted as inclusion of WDG increased from 15 to 30%; however, diets containing 15% CDG or SDG had no effect on apparent total tract digestion of DM, OM, CP, NDF, and starch compared with an SFC control diet. Spiehs and Shurson (2002) reported S contents ranging from 0.33 to 0.74% in dry distillers grains. Similarly Holt and Pritchard (2004) reported that S ranged from 0.35 to 0.69% for dry distillers grains with solubles, 0.36 to 0.39 for WDG, and 0.25 to 1.15% for condensed distillers solubles. Increasing S concentration from inorganic sources such as Na2SO4 increases H2S produced in vitro (Kung et al., 1998; Quinn et al., 2009; Smith et al., 2009), but the effects of increased concentrations of S in WDG on H2S production have not been evaluated. We hypothesized that increasing WDG concentration in substrates containing SFC would increase in vitro H2S production and that the greater fiber concentration in WDG would affect in vitro fermentation. Thus, the objective was to quantify in vitro total gas and H2S production, IVDMD, and VFA proportions and concentrations in SFC-based substrates that contained 15 or 30% (DM basis) CDG and SDG. MATERIALS AND METHODS All procedures involving live animals were approved by the Texas Tech University Animal Care and Use Committee. Feed ingredients consisting of SFC, cottonseed meal, CDG, SDG, and corn oil were used to mix 5 treatment substrates for in vitro fermentation studies (Table 1). All substrates were balanced for ether extract and degraded intake protein (DIP; approximately 8%) based on tabular values (NRC, 1996). The 5 substrates were arranged in a 2 × 2 + 1 factorial arrangement, resulting in the following treatments (DM basis): no WDG (CON), 15% CDG, 15% SDG, 30% CDG, and 30% SDG. The average DM of the CDG (Quality Distillers Grains, Hereford, TX) and SDG (Abengoa Bioenergy, Portales, NM) during the companion feeding experiment (May et al., 2010) was 31.2 and 28.7%, respectively. For the present study, samples of the CDG and SDG used during the feeding experiment were dried in a forced-air oven for 24 h at 50°C before being mixed into the substrates. The remaining ingredients (excluding corn oil) were placed on a flat surface and dried with an electric fan blowing air across the surface of the samples for 48 h. Ingredients were ground to pass a 2-mm screen in a Wiley mill and mixed into their respective substrates. Substrates were sent to a commercial laboratory for analysis (Table 1; SDK Laboratories, Hutchinson, KS). Analyses performed on the treatment substrates were as follows: N (FP-200, Leco Corp., St. Joseph, MI) using official method 992.15 (AOAC, 1995); Ca and K using official method 968.08 (AOAC, 1995); P using official method 965.17 (AOAC, 1995); S using official method 985.01 (AOAC, 1995); and ether extract using official method 920.39 (AOAC, 1995). Determination of ADF was conducted using an Ankom 200 Fiber Analyzer according to the procedures of Goering and Van Soest (1970; as modified by Ankom Technology Corp., Macedon, NY). Table 1. Composition and analyzed nutrient content (DM basis) of the treatment substrates used for the in vitro incubations Item  Treatment substrate1  CON  CDG-15  CDG-30  SDG-15  SDG-30  Ingredient, %             Steam-flaked corn  88.16  77.87  69.43  77.63  69.98   Corn WDG  —  15.00  30.00  —  —   Sorghum WDG  —  —  —  15.00  30.00   Cottonseed meal  8.00  5.00  —  5.00  —   Urea  0.89  0.66  0.57  0.62  0.50   Corn oil  2.95  1.47  —  1.75  0.52  Analyzed composition,2 %             DM  93.3  90.7  93.1  91.4  92.4   CP  12.1  13.9  15.5  15.1  17.3   ADF  4.8  5.5  7.7  7.5  9.6   Ether extract  4.6  6.4  6.5  6.4  6.2   Ca  0.03  0.02  0.01  0.03  0.03   P  0.29  0.35  0.43  0.36  0.38   K  0.41  0.43  0.48  0.44  0.47   S  0.13  0.19  0.29  0.22  0.31  Item  Treatment substrate1  CON  CDG-15  CDG-30  SDG-15  SDG-30  Ingredient, %             Steam-flaked corn  88.16  77.87  69.43  77.63  69.98   Corn WDG  —  15.00  30.00  —  —   Sorghum WDG  —  —  —  15.00  30.00   Cottonseed meal  8.00  5.00  —  5.00  —   Urea  0.89  0.66  0.57  0.62  0.50   Corn oil  2.95  1.47  —  1.75  0.52  Analyzed composition,2 %             DM  93.3  90.7  93.1  91.4  92.4   CP  12.1  13.9  15.5  15.1  17.3   ADF  4.8  5.5  7.7  7.5  9.6   Ether extract  4.6  6.4  6.5  6.4  6.2   Ca  0.03  0.02  0.01  0.03  0.03   P  0.29  0.35  0.43  0.36  0.38   K  0.41  0.43  0.48  0.44  0.47   S  0.13  0.19  0.29  0.22  0.31  1CON = standard steam-flaked corn-based substrate; CDG-15 = steam-flaked corn-based substrate with 15% (DM basis) corn wet distillers grains with solubles (WDG); CDG-30 = steam-flaked corn-based substrate with 30% (DM basis) corn WDG; SDG-15 = steam-flaked corn-based substrate with 15% (DM basis) sorghum WDG; SDG-30 = steam-flaked corn-based substrate with 30% (DM basis) sorghum WDG. 2Analyzed by SDK Laboratories (Hutchinson, KS). View Large Table 1. Composition and analyzed nutrient content (DM basis) of the treatment substrates used for the in vitro incubations Item  Treatment substrate1  CON  CDG-15  CDG-30  SDG-15  SDG-30  Ingredient, %             Steam-flaked corn  88.16  77.87  69.43  77.63  69.98   Corn WDG  —  15.00  30.00  —  —   Sorghum WDG  —  —  —  15.00  30.00   Cottonseed meal  8.00  5.00  —  5.00  —   Urea  0.89  0.66  0.57  0.62  0.50   Corn oil  2.95  1.47  —  1.75  0.52  Analyzed composition,2 %             DM  93.3  90.7  93.1  91.4  92.4   CP  12.1  13.9  15.5  15.1  17.3   ADF  4.8  5.5  7.7  7.5  9.6   Ether extract  4.6  6.4  6.5  6.4  6.2   Ca  0.03  0.02  0.01  0.03  0.03   P  0.29  0.35  0.43  0.36  0.38   K  0.41  0.43  0.48  0.44  0.47   S  0.13  0.19  0.29  0.22  0.31  Item  Treatment substrate1  CON  CDG-15  CDG-30  SDG-15  SDG-30  Ingredient, %             Steam-flaked corn  88.16  77.87  69.43  77.63  69.98   Corn WDG  —  15.00  30.00  —  —   Sorghum WDG  —  —  —  15.00  30.00   Cottonseed meal  8.00  5.00  —  5.00  —   Urea  0.89  0.66  0.57  0.62  0.50   Corn oil  2.95  1.47  —  1.75  0.52  Analyzed composition,2 %             DM  93.3  90.7  93.1  91.4  92.4   CP  12.1  13.9  15.5  15.1  17.3   ADF  4.8  5.5  7.7  7.5  9.6   Ether extract  4.6  6.4  6.5  6.4  6.2   Ca  0.03  0.02  0.01  0.03  0.03   P  0.29  0.35  0.43  0.36  0.38   K  0.41  0.43  0.48  0.44  0.47   S  0.13  0.19  0.29  0.22  0.31  1CON = standard steam-flaked corn-based substrate; CDG-15 = steam-flaked corn-based substrate with 15% (DM basis) corn wet distillers grains with solubles (WDG); CDG-30 = steam-flaked corn-based substrate with 30% (DM basis) corn WDG; SDG-15 = steam-flaked corn-based substrate with 15% (DM basis) sorghum WDG; SDG-30 = steam-flaked corn-based substrate with 30% (DM basis) sorghum WDG. 2Analyzed by SDK Laboratories (Hutchinson, KS). View Large Collection of Ruminal Fluid Ruminal fluid used in the various in vitro fermentation methods was collected from 2 ruminally cannulated Jersey crossbred steers (BW = approximately 320 kg) fitted with 7.62-cm ruminal cannula. The steers were housed at the Texas Tech University Burnett Research Center in New Deal, TX, and were fed a 75% concentrate diet that contained SFC, cottonseed meal, ground alfalfa hay, and cottonseed hulls as the basal ingredients. The steers were acclimated to the diet for a minimum of 28 d before the first collection of ruminal contents and remained on the diet throughout the sampling period. Water was provided free choice, and fresh feed was provided once daily, with a DMI of approximately 2.4% of BW. Ruminal fluid was collected approximately 4 h after feeding, strained through 4 layers of cheesecloth, and immediately placed in a sealed Thermos for transport to the Ruminant Nutrition Laboratory (Lubbock, TX). Within approximately 30 min after sampling, the fluid was used for the culture inoculum. General Procedures A modified procedure based on the method of Tilley and Terry (1963) was used for all 3 in vitro systems. A 24-h incubation period was chosen because with the SFC-based substrates used in the experiment, this incubation time is similar to the value reported by Ramirez et al. (1985) for ruminal mean retention time of dysprosium-labeled SFC: 24.3 h. Moreover, Ramirez et al. (1985) and Brown et al. (1998) observed that 85 to 95% of grain IVDMD occurred in a 24-h incubation period. Duplicate samples (1 ± 0.05 g) of each substrate were dried using a forced-air oven for 24 h at 100°C to determine substrate DM. The total gas and H2S production measurements and VFA analyses were replicated on 2 separate days, whereas the IVDMD and Ankom Gas Pressure Monitor measurements were replicated on 3 separate days. Within each day, tubes or bottles were incubated in triplicate to estimate the sampling error (with the exception of the continuous-pressure monitoring system flasks, which were incubated in duplicate). Total Gas and H2S Production Approximately 0.7 ± 0.01 g of substrate was weighed and placed in a 125-mL serum bottle. McDougall's buffer (37.5 mL; McDougall, 1948) and 12.5 mL of ruminal fluid (3:1 buffer:ruminal fluid ratio) were added to each serum vial, after which the vial was flushed with CO2. Two blanks were used in each run and were treated similarly to the treatment serum vials but with no substrate added, which provided an estimate of gas production and H2S production contributed by the inoculum. The vials were then capped with a butyl rubber stopper and crimp-sealed, after which they were incubated in an oscillating shaker (Environ-Shaker, Lab-Line Industries, Melrose Park, IL) for 24 h at 39°C with an oscillation speed of 125 rpm. Serum vials were removed from the oscillating shaker after the 24-h incubation, and total gas produced was measured by puncturing the butyl rubber stopper with a 16-gauge needle on the end of a plastic tubing line that was attached to an inverted, water-filled 250-mL burette. After gas release, a 5-mL syringe fitted with a 2-way valve was used to collect a 5-mL gas sample from the headspace of each serum bottle, and the syringe valve was closed to prevent contamination. The syringe needle was then inserted into a 15-mL evacuated tube (BD Vacutainer, Becton Dickinson and Co., Franklin Lakes, NJ), and the gas sample was slowly bubbled into 5 mL of alkaline water (distilled water that was brought to pH 8 with 0.1 N NaOH) that had previously been placed inside the evacuated tube. Subsequently, 0.5 mL of ferric chloride solution and 0.5 mL of N,N-dimethyl-p-phenylenediamine dihydrochloride sulfate were added to the 15-mL Vacutainer tube. Methylene blue is formed by sulfide reacting with N,N-dimethyl-p-phenylenediamine dihydrochloride in the presence of ferric chloride (Siegel, 1965). Hydrogen sulfide concentrations were determined as described by Quinn et al. (2009), with the reagent blank and standards solutions read at a wavelength of 665 nm with a Beckman DU-50 spectrophotometer (Beckman Instruments Inc., Irvine, CA). Each sample was corrected for fermentable DM (using the IVDMD described in a subsequent section) and H2S introduced into the system from ruminal fluid (based on blank samples). IVDMD For the IVDMD measurements (adapted from Galyean, 1997), 0.5 ± 0.05 g of substrate was weighed into a 50-mL polyethylene centrifuge tube. The ruminal fluid:buffer ratio was the same as for gas production measurements; however, the total volume was only 36 mL. Two blanks (no substrate but the same inoculum volume) were included in each run. Tubes were flushed with CO2 and capped with rubber stoppers equipped with a 16-gauge needle for gas release, after which they were incubated for 24-h in a 39°C water bath with an oscillation speed of 70 rpm (Precision Model 25 Reciprocal Shaking Bath, Precision Instruments, Winchester, VA). After incubation, tubes were centrifuged at 2,000 × g for 15 min at 4°C. The supernatant fluid was removed, and 35 mL of an acidified pepsin solution (prepared by adding 6.6 g of 1:3,000 pepsin and 100 mL of 1 N HCl and diluted to 1 L with distilled water) were added to each tube, followed by incubation for 48 h at 39°C. After pepsin digestion, samples were filtered (541 ashless, Whatman International Ltd., Kent, ME) to obtain the residue remaining in each tube. The filter papers and residue were dried at 100°C for 24 h and weighed. The IVDMD (%) was calculated as 100 × [(initial sample dry weight − residue-blank)/initial sample dry weight]. In Vitro Kinetics of Gas Production Twelve gas pressure monitor modules (Ankom Technology Corp.) were used in duplicate for the 5 treatment diets, with 2 blank modules for each of 3 replicate days. Each 250-mL flask received 0.7 ± 0.01 g of substrate, 37.5 mL of McDougall's buffer (McDougall, 1948), and 12.5 mL of strained ruminal fluid, after which each flask was flushed with CO2. After addition of the substrate and inoculum, each module was purged with CO2, securely fastened to the Ankom pressure monitor cap, and placed into an oscillating shaker (Environ-Shaker, Lab-Line Industries) for 24 h at 39°C, with an oscillation speed of 125 rpm. Each remote wireless module of the Ankom system sends gas pressure data to a base coordinator unit (Gas Pressure Monitor, Ankom Technology Corp.) attached to a personal computer. In addition, each module is fitted with a pressure valve, and the valves release gas at a predetermined pressure setting (20.7 kPa) to eliminate pressure buildup within the flask. Pressure for each module was recorded every 30 min during the 24-h period, and the computer software monitored the pressure that was released, which allowed for software-based calculation of the cumulative gas production. After completion of each run, the data were stored in a spreadsheet file and converted from pressure readings to milliliters of gas produced per gram of DM incubated using the following equation (Lopez et al., 2007):  where G is gas volume, Vh is headspace volume, Pa is atmospheric pressure, and Pt is pressure measured by the transducer. VFA Analysis The contents of each 125-mL serum vial from the gas production phase of the experiment were retained, and 0.5 mL of a 20% (vol/vol) H2SO4 solution was added to stop fermentation. These samples were frozen and subsequently analyzed by gas chromatography for VFA concentrations (Shimadzu GC-8A, Shimadzu Scientific Instruments Inc., Columbia, MD; Supelco SP-1200, 2 m × 5 mm × 2.6 mm glass column, Supelco, Bellefonte, PA). Sample preparation methods and analytical procedures were as described by Goetsch and Galyean (1983). Statistical Analyses and Calculations In vitro VFA data were used to estimate the quantity of hexose equivalent fermented (mol/100 mol of VFA produced), as well as CH4, and CO2 produced (mol/mol of hexose fermented) using fermentation balance calculations from Wolin (1960). The calculations were modified to account for the H associated with H2S produced during fermentation. A modified Gompertz model (Schofield et al., 1994; Huhtanen et al., 2008) was fitted (NLIN procedure, SAS Inst., Inc., Cary, NC) to data from the Ankom Gas Pressure system. Parameters of this model included lag time (h), asymptotic gas production (V), and rate of gas production (k). Fractional rate of gas production was calculated as k divided by V. The MIXED procedure of SAS was used to analyze total gas and H2S production, IVDMD, VFA, fermentation balance calculations, and the lag and fractional rate parameter estimates from the nonlinear model for gas kinetics data. Sampling units were each respective vial, module, or tube, with n = 2 replications per treatment for gas production kinetics, and n = 3 replications per treatment for other measurements. Procedures were repeated on 2 or 3 separate days to provide true statistical replication. For cases with 3 d of measurements, the model included the random effect of day (i.e., replicate in time) and treatment as a fixed effect, whereas replicate in time was considered a fixed effect for cases in which 2 d of measurements were available. Preplanned orthogonal contrasts were used to compare 1) CON vs. the average of other treatments; 2) the source of WDG (CDG vs. SDG); 3) the WDG concentration (15 vs. 30%); and 4) the interaction between WDG source and concentration. An α level of 0.05 was used to determine significance, with tendencies associated with P-values between 0.05 and 0.10. Because of space limitations, significance levels in tables are expressed as P < 0.05 and 0.05 < P ≤ 0.10; however, observed P-values for contrasts are provided in the text. RESULTS AND DISCUSSION Substrate Composition Analyzed substrate composition values generally agreed with expected values based on formulation (Table 1), with the exception of the ether extract concentration. Substrates were balanced for ether extract; however, the analyzed ether extract of the CON substrate was less than formulated (4.62% ether extract vs. and an average of 6.36% for the substrates that contained WDG). Accurately weighed quantities of each ingredient were used to prepare the treatment substrates, so the less than expected ether extract value for the CON substrate is perplexing. The difference most likely reflects the difficulty of mixing corn oil uniformly and subsequently obtaining a representative sample for chemical analyses. Treatment substrates were balanced to yield similar tabular DIP values (approximately 8% DIP), but not for CP. As a result, when WDG inclusion increased, CP concentration also increased. Moreover, S content increased as WDG increased, which was expected from the S concentration in the CDG and SDG used to prepare the substrates. Results for the various in vitro measurements are presented in Table 2. No significant interactions were detected between WDG source and WDG inclusion (P ≥ 0.14). Simple-effect means are shown in the tables, and results are presented and discussed in the context of the preplanned contrasts described previously. Table 2. Effects of 15 or 30% corn or sorghum wet distillers grains with solubles (WDG) on in vitro fermentation measurements Item  Treatment substrate1  SEM2  Contrast3  CON  CDG-15  CDG-30  SDG-15  SDG-30  IVDMD, %  70.3  67.4  64.6  64.3  62.9  0.88  DG*, GS*, LV*  H2S, µmol/g of fermentable DM  3.5  5.1  7.6  5.7  7.4  0.39  DG*, LV*  Gas production, mL/g of substrate DM  194.4  190.4  180.0  186.2  180.3  1.59  DG*, LV*  Gas production kinetics4                 k, %/h  5.83  5.52  5.33  5.28  5.39  0.317  NS   Lag, h  0.80  0.70  0.77  0.42  0.95  0.167  NS  Item  Treatment substrate1  SEM2  Contrast3  CON  CDG-15  CDG-30  SDG-15  SDG-30  IVDMD, %  70.3  67.4  64.6  64.3  62.9  0.88  DG*, GS*, LV*  H2S, µmol/g of fermentable DM  3.5  5.1  7.6  5.7  7.4  0.39  DG*, LV*  Gas production, mL/g of substrate DM  194.4  190.4  180.0  186.2  180.3  1.59  DG*, LV*  Gas production kinetics4                 k, %/h  5.83  5.52  5.33  5.28  5.39  0.317  NS   Lag, h  0.80  0.70  0.77  0.42  0.95  0.167  NS  1CON = standard steam-flaked corn-based substrate; CDG-15 = steam-flaked corn-based substrate with 15% (DM basis) corn WDG; CDG-30 = steam-flaked corn-based substrate with 30% (DM basis) corn WDG; SDG-15 = steam-flaked corn-based substrate with 15% (DM basis) sorghum WDG; SDG-30 = steam-flaked corn-based substrate with 30% (DM basis) sorghum WDG. 2Pooled SE of main-effect means; n = 2 replications per treatment for gas production kinetics, and n = 3 replications per treatment for other measurements. 3Orthogonal contrasts: DG = control vs. the average of all other diets; GS = the average of the CDG-15 and CDG-30 diets vs. the average of the SDG-15 and SDG-30 diets; LV = the average of diets with CDG-15 and SDG-15 vs. the average of the CDG-30 and SDG-30 diets. 4Parameters were estimated by fitting a modified Gompertz function, with k = fractional rate of fermentation, and Lag = duration of the lag phase. *P ≤ 0.05; NS = P > 0.10. View Large Table 2. Effects of 15 or 30% corn or sorghum wet distillers grains with solubles (WDG) on in vitro fermentation measurements Item  Treatment substrate1  SEM2  Contrast3  CON  CDG-15  CDG-30  SDG-15  SDG-30  IVDMD, %  70.3  67.4  64.6  64.3  62.9  0.88  DG*, GS*, LV*  H2S, µmol/g of fermentable DM  3.5  5.1  7.6  5.7  7.4  0.39  DG*, LV*  Gas production, mL/g of substrate DM  194.4  190.4  180.0  186.2  180.3  1.59  DG*, LV*  Gas production kinetics4                 k, %/h  5.83  5.52  5.33  5.28  5.39  0.317  NS   Lag, h  0.80  0.70  0.77  0.42  0.95  0.167  NS  Item  Treatment substrate1  SEM2  Contrast3  CON  CDG-15  CDG-30  SDG-15  SDG-30  IVDMD, %  70.3  67.4  64.6  64.3  62.9  0.88  DG*, GS*, LV*  H2S, µmol/g of fermentable DM  3.5  5.1  7.6  5.7  7.4  0.39  DG*, LV*  Gas production, mL/g of substrate DM  194.4  190.4  180.0  186.2  180.3  1.59  DG*, LV*  Gas production kinetics4                 k, %/h  5.83  5.52  5.33  5.28  5.39  0.317  NS   Lag, h  0.80  0.70  0.77  0.42  0.95  0.167  NS  1CON = standard steam-flaked corn-based substrate; CDG-15 = steam-flaked corn-based substrate with 15% (DM basis) corn WDG; CDG-30 = steam-flaked corn-based substrate with 30% (DM basis) corn WDG; SDG-15 = steam-flaked corn-based substrate with 15% (DM basis) sorghum WDG; SDG-30 = steam-flaked corn-based substrate with 30% (DM basis) sorghum WDG. 2Pooled SE of main-effect means; n = 2 replications per treatment for gas production kinetics, and n = 3 replications per treatment for other measurements. 3Orthogonal contrasts: DG = control vs. the average of all other diets; GS = the average of the CDG-15 and CDG-30 diets vs. the average of the SDG-15 and SDG-30 diets; LV = the average of diets with CDG-15 and SDG-15 vs. the average of the CDG-30 and SDG-30 diets. 4Parameters were estimated by fitting a modified Gompertz function, with k = fractional rate of fermentation, and Lag = duration of the lag phase. *P ≤ 0.05; NS = P > 0.10. View Large IVDMD A decrease in IVDMD was noted for substrates containing WDG vs. CON (P < 0.001; Table 2). In addition, as WDG increased from 15 to 30% of the substrate DM, IVDMD decreased (P = 0.05), and within WDG-containing substrates, IVDMD was greater for CDG than for SDG (P = 0.03). The decreased IVDMD of WDG substrates vs. CON, and the effect of WDG concentration most likely resulted from the increased concentration of ADF and decreased starch content when either source of WDG replaced SFC in the CON substrate. In addition, the ADF content of SDG substrates was greater than for CDG substrates (Table 1), which is consistent with the difference in IVDMD between the 2 sources. In a companion study, May et al. (2010) fed feedlot cattle diets containing CDG, SDG, and a 50:50 blend of CDG:SDG at 15 or 30% of the dietary DM. Cattle fed distillers grains had less ADG, DMI, G:F, final BW, and HCW than those fed an SFC-based control diet. In addition, as the concentration of WDG increased from 15 to 30%, G:F, final BW, HCW, and calculated dietary concentrations of NEg and NEm decreased. May et al. (2010) also noted that cattle fed SDG had decreased G:F and NE values compared with those fed CDG. Thus, the effects of inclusion amount and source of WDG on IVDMD in the present study may help explain differences in cattle performance reported in the companion study. The results in the current study are also supported by the findings of Leibovich et al. (2009), who reported decreased IVDMD in substrates with 15% SDG compared with the control substrates containing no SDG. In contrast to the present IVDMD results, in the companion study by May et al. (2010), no differences were reported in apparent total tract digestion of DM, OM, ADF, or starch by steers fed an SFC-based control diet vs. diets with 15% CDG or SDG. Although not measured in the present study, culture pH has been shown to affect IVDMD when distillers grains are used as a portion of the substrate. Uwituze et al. (2008) incubated a 50:50 mixture of dry-rolled corn (DRC) and dry corn distillers grains with solubles for 6, 12, 24, and 48 h at 3 pH values (5, 5.5, and 6) and reported that IVDMD decreased significantly as pH decreased. Because in vitro systems do not mimic postruminal digestion, perhaps these IVDMD results reflect changes in ruminal disappearance of nutrients, with an expected decrease in fiber digestion, whereas the in vivo data of May et al. (2010) reflect compensatory digestion (particularly fiber) in the lower small intestine and large intestine. Total Gas and H2S Production Hydrogen sulfide production (μmol/g of fermentable DM) was greater for substrates containing WDG than for CON (P = 0.003; Table 2), and increased H2S production was also noted when WDG concentration increased from 15 to 30% (P = 0.01). No differences (P = 0.66) were detected between CDG and SDG for H2S production, suggesting that S concentration of the substrate is likely the most important factor contributing to in vitro H2S production. The S content of each substrate was similar within the amount of WDG (Table 1), reflecting the lack of a source effect. Gould (1998) suggested that it is important to monitor the concentration of S in the diet, but also noted that ruminal pH might affect the occurrence of polioencephalomalacia because low pH seems to favor reduction of S to H2S in the rumen. Decreased animal performance when feeding high-S diets was reported by Uwituze et al. (2009), who fed diets that contained 30% (DM basis) dry corn distillers grains with solubles, and thereby greater S concentrations, than in the present study. Dietary S concentrations were 0.42 and 0.65% (increased S was achieved by adding H2SO4 to distillers grains), and the authors observed decreased DMI, ADG, and HCW as a consequence of feeding the diet with increased S. There was also an increase in ruminal H2S production in cattle fed diets with the greater S concentrations. Loneragan et al. (2001) observed linear decreases in ADG, G:F, final BW, HCW, and dressing percent in feedlot cattle as the sulfate concentration in drinking water increased from 136 to 2,360 mg/L (0.18 to 0.40% dietary S). In cattle fed high-concentrate diets containing 0.15, 0.20, and 0.25% dietary S, Zinn et al. (1997) reported linear decreases in ADG, DMI, G:F, HCW, and LM area with increasing S. Our in vitro results for greater H2S production with increasing S concentration in the substrate are supported by the results of other in vitro experiments (Kung et al., 2000: 0.29 and 1.09% substrate S; Quinn et al., 2009: 0.17 and 0.42% substrate S; Smith et al., 2009: 0.2, 0.4, and 0.8% substrate S). However, previous in vitro studies used Na2SO4 to increase S concentration, whereas results from the current study reflect the effects of S from WDG on in vitro H2S production. In contrast to findings in the current study, Leibovich et al. (2009) reported no difference for in vitro H2S production between diets containing no SDG vs. 15% SDG. The discrepancy between the present experiment and the observations of Leibovich et al. (2009) is likely attributable to the relatively small difference in S concentration of their substrates (0.20 to 0.24% substrate S). Inclusion of WDG in treatment substrates resulted in decreased total gas production per unit of substrate DM compared with the CON substrate (P = 0.005; Table 2). In addition, increasing the concentration of WDG from 15 to 30% decreased total gas production (P = 0.007). These results are similar to the results for IVDMD described previously and, as also noted previously, likely reflect the greater fiber concentration in substrates that contained WDG. When the gas production data were corrected for differences in IVDMD (i.e., gas produced/g of fermentable DM), WDG substrates had increased values compared with the CON substrate (P = 0.01; data not shown). In addition, there was a tendency (P = 0.069) for SDG substrates to have greater total gas production per gram of fermentable DM than CDG substrates, reflecting the decreased IVDMD and greater ADF content of SDG vs. CDG (Table 1). In Vitro Kinetics of Gas Production Treatments did not differ for calculated lag time or the fractional rate of gas production (P > 0.12; Table 2); however, the numerical trend was for rates to be less with substrates containing WDG vs. the SFC control, thereby reflecting the decrease in IVDMD reported previously. Similarly, Leibovich et al. (2009) observed no differences in lag time when 0 or 15% SDG in SFC-based substrates were incubated in the same gas production system as in the current study. We did not analyze the asymptotic gas production estimate from the nonlinear model because the incubation period of 24 h was likely not sufficient for gas production to reach an asymptote, which would affect the precision and accuracy of the asymptotic gas production parameter estimate. VFA and Fermentation Balance Calculations With the exception of isobutyrate, molar proportions of VFA did not differ among treatments (P > 0.18; Table 3). Furthermore, total VFA concentration and the acetate:propionate ratio did not differ among treatments (P > 0.32). The molar proportion of isobutyrate was greater for substrates containing CDG vs. SDG (P = 0.04), and there was a tendency (P = 0.08) for the CON treatment to have less isobutyrate than the treatments containing WDG. The molar proportions of isobutyrate were small for all treatments, and the practical significance of the differences is not clear. May et al. (2009) did not observe differences in isobutyrate with 25% (DM basis) dry corn distillers grains with solubles vs. a control diet with no distillers grains. These VFA data are typical of those expected with fermentation of high-grain, low-roughage diets, with an increased molar proportion of propionate relative to acetate (Sutton et al., 2003). The lack of treatment differences in VFA suggests that the decreased IVDMD and gas production and the greater fiber concentration of WDG diets did not appreciably affect the in vitro fermentation pattern. Table 3. Effects of 15 or 30% corn or sorghum wet distillers grains with solubles (WDG) on molar proportions (mol/100 mol) of VFA, total VFA concentration (mM), and fermentation balance calculations Item  Treatment1  SEM2  Contrast3  CON  CDG-15  CDG-30  SDG-15  SDG-30  Acetate  42.0  42.8  42.4  43.5  43.0  1.65  NS  Propionate  40.7  39.4  38.3  39.2  39.0  1.10  NS  Isobutyrate  0.7  1.0  1.4  0.9  0.8  0.12  GS*, DG†  Butyrate  12.1  12.2  13.0  12.0  12.7  0.48  NS  Isovalerate  2.3  2.3  2.6  2.2  2.3  0.17  NS  Valerate  2.2  2.3  2.5  2.2  2.3  0.09  NS  Total VFA  136.7  148.6  124.6  141.6  144.6  14.31  NS  Acetate:propionate  1.1  1.1  1.2  1.2  1.2  0.08  NS  Hexose fermented4  58.6  58.9  59.7  58.7  59.0  0.38  NS  Carbon dioxide4  0.95  0.96  0.98  0.96  0.97  0.005  DG†, LV†  Methane4  0.27  0.29  0.29  0.29  0.29  0.017  NS  Item  Treatment1  SEM2  Contrast3  CON  CDG-15  CDG-30  SDG-15  SDG-30  Acetate  42.0  42.8  42.4  43.5  43.0  1.65  NS  Propionate  40.7  39.4  38.3  39.2  39.0  1.10  NS  Isobutyrate  0.7  1.0  1.4  0.9  0.8  0.12  GS*, DG†  Butyrate  12.1  12.2  13.0  12.0  12.7  0.48  NS  Isovalerate  2.3  2.3  2.6  2.2  2.3  0.17  NS  Valerate  2.2  2.3  2.5  2.2  2.3  0.09  NS  Total VFA  136.7  148.6  124.6  141.6  144.6  14.31  NS  Acetate:propionate  1.1  1.1  1.2  1.2  1.2  0.08  NS  Hexose fermented4  58.6  58.9  59.7  58.7  59.0  0.38  NS  Carbon dioxide4  0.95  0.96  0.98  0.96  0.97  0.005  DG†, LV†  Methane4  0.27  0.29  0.29  0.29  0.29  0.017  NS  1CON = standard steam-flaked corn-based substrate; CDG-15 = steam-flaked corn-based substrate with 15% (DM basis) corn WDG; CDG-30 = steam-flaked corn-based substrate with 30% (DM basis) corn WDG; SDG-15 = steam-flaked corn-based substrate with 15% (DM basis) sorghum WDG; SDG-30 = steam-flaked corn-based substrate with 30% (DM basis) sorghum WDG. 2Pooled SE of main-effect means; n = 2 replications per treatment. 3Orthogonal contrasts: DG = control vs. the average of all other diets; GS = the average of the CDG-15 and CDG-30 diets vs. the average of the SDG-15 and SDG-30 diets; LV = the average of diets with CDG-15 and SDG-15 vs. the average of the CDG-30 and SDG-30 diets. 4Hexose fermented (mol/100 mol of VFA), and carbon dioxide and methane (mol/mol of hexose fermented) were calculated from molar proportions of VFA using the fermentation balance equations described by Wolin (1960). *P ≤ 0.05; †0.05 < P ≤ 0.10; NS = P > 0.10. View Large Table 3. Effects of 15 or 30% corn or sorghum wet distillers grains with solubles (WDG) on molar proportions (mol/100 mol) of VFA, total VFA concentration (mM), and fermentation balance calculations Item  Treatment1  SEM2  Contrast3  CON  CDG-15  CDG-30  SDG-15  SDG-30  Acetate  42.0  42.8  42.4  43.5  43.0  1.65  NS  Propionate  40.7  39.4  38.3  39.2  39.0  1.10  NS  Isobutyrate  0.7  1.0  1.4  0.9  0.8  0.12  GS*, DG†  Butyrate  12.1  12.2  13.0  12.0  12.7  0.48  NS  Isovalerate  2.3  2.3  2.6  2.2  2.3  0.17  NS  Valerate  2.2  2.3  2.5  2.2  2.3  0.09  NS  Total VFA  136.7  148.6  124.6  141.6  144.6  14.31  NS  Acetate:propionate  1.1  1.1  1.2  1.2  1.2  0.08  NS  Hexose fermented4  58.6  58.9  59.7  58.7  59.0  0.38  NS  Carbon dioxide4  0.95  0.96  0.98  0.96  0.97  0.005  DG†, LV†  Methane4  0.27  0.29  0.29  0.29  0.29  0.017  NS  Item  Treatment1  SEM2  Contrast3  CON  CDG-15  CDG-30  SDG-15  SDG-30  Acetate  42.0  42.8  42.4  43.5  43.0  1.65  NS  Propionate  40.7  39.4  38.3  39.2  39.0  1.10  NS  Isobutyrate  0.7  1.0  1.4  0.9  0.8  0.12  GS*, DG†  Butyrate  12.1  12.2  13.0  12.0  12.7  0.48  NS  Isovalerate  2.3  2.3  2.6  2.2  2.3  0.17  NS  Valerate  2.2  2.3  2.5  2.2  2.3  0.09  NS  Total VFA  136.7  148.6  124.6  141.6  144.6  14.31  NS  Acetate:propionate  1.1  1.1  1.2  1.2  1.2  0.08  NS  Hexose fermented4  58.6  58.9  59.7  58.7  59.0  0.38  NS  Carbon dioxide4  0.95  0.96  0.98  0.96  0.97  0.005  DG†, LV†  Methane4  0.27  0.29  0.29  0.29  0.29  0.017  NS  1CON = standard steam-flaked corn-based substrate; CDG-15 = steam-flaked corn-based substrate with 15% (DM basis) corn WDG; CDG-30 = steam-flaked corn-based substrate with 30% (DM basis) corn WDG; SDG-15 = steam-flaked corn-based substrate with 15% (DM basis) sorghum WDG; SDG-30 = steam-flaked corn-based substrate with 30% (DM basis) sorghum WDG. 2Pooled SE of main-effect means; n = 2 replications per treatment. 3Orthogonal contrasts: DG = control vs. the average of all other diets; GS = the average of the CDG-15 and CDG-30 diets vs. the average of the SDG-15 and SDG-30 diets; LV = the average of diets with CDG-15 and SDG-15 vs. the average of the CDG-30 and SDG-30 diets. 4Hexose fermented (mol/100 mol of VFA), and carbon dioxide and methane (mol/mol of hexose fermented) were calculated from molar proportions of VFA using the fermentation balance equations described by Wolin (1960). *P ≤ 0.05; †0.05 < P ≤ 0.10; NS = P > 0.10. View Large These VFA results are similar to the in vivo data of May et al. (2009), who observed no differences in the VFA profile in cattle fed SFC- or DRC-based diets with or without 25% dry corn distillers grains with solubles. In contrast, Corrigan et al. (2009) and Vander Pol et al. (2009) reported that feeding WDG altered ruminal in vivo VFA patterns. In a metabolism study, Corrigan et al. (2009) fed diets containing DRC, high-moisture corn, or SFC that contained 0 or 40% CDG. With the DRC and high-moisture corn diets that contained CDG, ruminal propionate molar proportions were similar to those in the SFC treatments. Likewise, in a metabolism study, Vander Pol et al. (2009) fed 40% CDG in DRC-based diets and observed decreased ruminal molar proportions of acetate and increased propionate with diets that contained CDG vs. a control diet without distillers grains. There were no differences among treatments in calculated hexose fermented or methane produced (P > 0.21; Table 3). There was a tendency (P = 0.06) for calculated CO2 production to be less for the CON treatments than for the other treatments. Moreover, there was a trend (P = 0.08) for the substrates containing 30% WDG to result in greater calculated CO2 production than the 15% WDG treatments. Increases in calculated CO2 with addition of WDG and increased concentration of WDG in the substrate resulted from small, nonsignificant increases in acetate and butyrate and might reflect the greater fiber concentration of the substrates containing WDG. Overall, the results of the current study suggest that increasing the WDG concentration in SFC-based substrates decreased IVDMD and total gas production. In addition, substrates with CDG seemed to be generally more digestible than those containing SDG. Hydrogen sulfide production in our in vitro system was predictable from substrate S concentration, with no evidence of differences between CDG and SDG. Molar proportions of VFA and associated fermentation balance calculations were not greatly affected by source or concentration of WDG. Caution must be exercised, however, in using results obtained with in vitro fermentation systems to draw conclusions about in vivo fermentation and digestion. Thus, further research is needed with in vivo measures of ruminal VFA patterns in diets containing different sources and concentrations of WDG. In addition, because in vitro methods cannot mimic digestive processes in the entire digestive tract, research designed to estimate the site and extent of digestion in vivo is needed to determine the extent to which our results reflect in vivo estimates of ruminal digestion in cattle fed diets with different WDG sources and concentrations. LITERATURE CITED AOAC 1995. Official Method of Analysis.  16th ed. Assoc. Off. Anal. Chem., Arlington, VA. Brown M. S. Galyean M. L. Duff G. C. Hallford D. M. 1998. Effects of degree of processing and nitrogen source and level on starch availability and in vitro fermentation of corn and sorghum grain. Prof. Anim. Sci.  14: 83– 94. Corrigan M. E. Erickson G. E. Klopfenstein T. J. Luebbe M. K. Vander Pol K. J. Meyer N. F. Buckner C. D. Vanness S. J. Hanford K. J. 2009. Effect of corn processing method and corn wet distillers grains plus solubles inclusion in finishing steers. J. Anim. Sci.  87: 3351– 3362. https://doi.org/19542508 Google Scholar CrossRef Search ADS PubMed  Depenbusch B. E. Loe E. R. Sindt J. J. Cole N. A. Higgins J. J. Drouilllard J. S. 2009. Optimizing use of distillers grains in finishing diets containing steam-flaked corn. J. Anim. Sci.  87: 2644– 2652. https://doi.org/19359511 Google Scholar CrossRef Search ADS PubMed  Galyean, M. L. 1997. Laboratory Procedures in Animal Nutrition Research.  Texas Tech Univ., Lubbock. http://apps.depts.ttu.edu/afs/home/mgalyean/lab_man.pdf Accessed Aug. 24, 2009. Goering, H. K., and P. J. Van Soest 1970. Forage Fiber Analyses (Apparatus, Reagents, Procedures, and Some Applications). Agric. Handb. No. 379.  USDA, ARS, Washington, DC. Goetsch A. L. Galyean M. L. 1983. Influence of feeding frequency on passage of fluid and particle markers in steers fed a concentrate diet. Can. J. Anim. Sci.  63: 727– 730. Google Scholar CrossRef Search ADS   Gould D. H. 1998. Polioencephalomalacia. J. Anim. Sci.  76: 309– 314. https://doi.org/9464912 Google Scholar CrossRef Search ADS PubMed  Holt, S. M., and R. H. Pritchard 2004. Composition and nutritive value of corn co-products from dry milling ethanol plants. Pages 1– 7 in SD Beef Rep. BEEF 2004-01.  South Dakota Agric. Exp. Stn., Brookings. Huhtanen P. Seppälä A. Ahvenjärvi S. Rinne M. 2008. Prediction of in vivo neutral detergent fiber digestibility and digestion rate of potentially digestible neutral detergent fiber: Comparison of models. J. Anim. Sci.  86: 2657– 2669. https://doi.org/18539835 Google Scholar CrossRef Search ADS PubMed  Klopfenstein T. J. Erickson G. E. Bremer V. R. 2008. BOARD-INVITED REVIEW: Use of distillers by-products in the beef cattle feeding industry. J. Anim. Sci.  86: 1223– 1231. https://doi.org/18156361 Google Scholar CrossRef Search ADS PubMed  Kung L. Bracht J. P. Tavares J. Y. 2000. Effects of various compounds on in vitro ruminal fermentation and production of sulfide. Anim. Feed Sci. Technol.  84: 69– 81. Google Scholar CrossRef Search ADS   Kung L. Hession A. O. Bracht J. P. 1998. Inhibition of sulfate reduction to sulfide by 9,10-anthraquinone in in vitro ruminal fermentations. J. Dairy Sci.  81: 2251– 2256. https://doi.org/9749391 Google Scholar CrossRef Search ADS PubMed  Leibovich J. Vasconcelos J. T. Galyean M. L. 2009. Effects of corn processing method in diets containing sorghum wet distillers grains plus solubles on performance and carcass characteristics of finishing beef cattle an on in vitro fermentation of diets. J. Anim. Sci.  87: 2124– 2132. https://doi.org/19251924 Google Scholar CrossRef Search ADS PubMed  Loneragan G. H. Wagner J. J. Gould D. H. Garry F. B. Thoren M. A. 2001. Effects of water sulfate concentration on performance, water intake, and carcass characteristics of feedlot steers. J. Anim. Sci.  79: 2941– 2948. https://doi.org/11811445 Google Scholar CrossRef Search ADS PubMed  Lopez S. Dahnoa M. S. Dijkstra J. Bannink A. Kebreab E. France J. 2007. Some methodological and analytical considerations regarding application of the gas production technique. Anim. Feed Sci. Technol.  135: 139– 156. Google Scholar CrossRef Search ADS   May M. L. Quinn M. J. Reinhardt C. D. Murray L. Gibson M. L. Karges K. K. Drouillard J. S. 2009. Effects of dry-rolled or steam-flaked corn finishing diets with or without twenty-five percent dried distillers grains on ruminal fermentation and apparent total tract digestion. J. Anim. Sci.  87: 3630– 3638. Google Scholar CrossRef Search ADS PubMed  McDougall E. I. 1948. Studies on ruminant saliva. 1. The composition and output of sheep's saliva. Biochem. J.  43: 99– 109. Google Scholar CrossRef Search ADS   NRC 1996. Nutrient Requirements of Beef Cattle.  7th ed. Natl. Acad. Press, Washington, DC. Quinn M. J. May M. L. Hales K. E. DiLorenzo N. Leibovich J. Smith D. R. Galyean M. L. 2009. Effects of ionophores and antibiotics on in vitro hydrogen sulfide production, dry matter disappearance, and total gas production in cultures with steam-flaked corn-based substrate with or without added sulfur. J. Anim. Sci.  87: 1705– 1713. Google Scholar CrossRef Search ADS PubMed  Ramirez R. G. Kiesling H. E. Galyean M. L. Lofgreen G. P. Elliott J. K. 1985. Influences of steam-flaked, steamed-whole, or whole shelled corn on performance and digestion in beef steers. J. Anim. Sci.  61: 1– 8. https://doi.org/4030513 Google Scholar CrossRef Search ADS PubMed  Schofield P. Pitt R. E. Pell A. N. 1994. Kinetics of fiber digestion from in vitro gas production. J. Anim. Sci.  72: 2980– 2991. https://doi.org/7730194 Google Scholar CrossRef Search ADS PubMed  Siegel L. M. 1965. A direct microdetermination for sulfide. Anal. Biochem.  11: 126– 132. https://doi.org/14328633 Google Scholar CrossRef Search ADS PubMed  Smith D. R. DiLorenzo N. Leibovich J. May M. L. Quinn M. J. Homm J. W. Galyean M. L. 2009. Effects of sulfur and monensin concentrations on in vitro dry matter disappearance, hydrogen sulfide production, and volatile fatty acid concentrations in batch culture ruminal fermentations. J. Anim. Sci.  88: 1503– 1512. Google Scholar CrossRef Search ADS PubMed  Spiehs M. J. M. H. W. Shurson G. C. 2002. Nutrient database for distillers dried grains with solubles produced from new ethanol plants in Minnesota and South Dakota. J. Anim. Sci.  80: 2639– 2645. https://doi.org/12413086 Google Scholar CrossRef Search ADS PubMed  Sutton J. D. Dhanoa M. S. Morant S. V. France J. Napper D. J. Schuller E. 2003. Rates of production of acetate, propionate, and butyrate in the rumen of lactating dairy cows given normal and low-roughage diets. J. Dairy Sci.  86: 3620– 3633. https://doi.org/14672193 Google Scholar CrossRef Search ADS PubMed  Tilley J. M. A. Terry R. A. 1963. A two-stage technique for the in vitro digestion of forage crops. J. Br. Grassl. Soc.  18: 104– 111. Google Scholar CrossRef Search ADS   Uwituze S. Heidenreich J. M. Nagaraja T. G. Higgins J. J. Drouillard J. S. 2008. Effect of controlled in vitro pH on fermentative activity of ruminal contents of finishing cattle adapted to supplemental dried distiller's grains. J. Anim. Sci.  86( E-Suppl. 3): 344. (Abstr.) Uwituze, S., M. K. Shelor, G. L. Parsons, K. K. Kargas, M. L. Gibson, L. C. Hollis, and J. S. Drouillard 2009. High sulfur content of dried distiller's grains with solubles impacts ruminal fermentation, feedlot cattle performance, and carcass characteristics.  Pages 105– 106 in Proc. Plains Nutr. Counc. Spring Conf., San Antonio, TX. Publ. No. AREC 09.18. Texas AgriLife Agric. Res. and Ext. Cent., Texas A&M System, Amarillo. (Abstr.) Vander Pol K. J. Luebbe M. K. Crawford G. I. Erickson G. E. Klopfenstein T. J. 2009. Performance and digestibility characteristics of finishing diets containing distillers grains, composites of corn processing coproducts, or supplemental corn oil. J. Anim. Sci.  87: 639– 652. https://doi.org/18952733 Google Scholar CrossRef Search ADS PubMed  Wolin M. J. 1960. A theoretical rumen fermentation balance. J. Dairy Sci.  43: 1452– 1459. Google Scholar CrossRef Search ADS   Zinn R. A. Alvarez E. Mendez M. Montaño M. Ramirez E. Shen Y. 1997. Influence of dietary sulfur level on growth performance and digestive function in feedlot cattle. J. Anim. Sci.  75: 1723– 1728. https://doi.org/9222827 Google Scholar CrossRef Search ADS PubMed  Footnotes 1 Supported in part by funding from a subcontract with Texas AgriLife Research, College Station. The Jessie W. Thornton Chair in Animal Science Endowment at Texas Tech University also provided funding to support this research. We thank DSM Nutritional Products (Belvidere, NJ), Elanco Animal Health (Greenfield, IN), Fort Dodge Animal Health (Overland Park, KS), Intervet/Schering-Plough (Millsboro, DE), and Kemin Industries (Des Moines, IA) for supplying products used in this research. The efforts of K. Robinson and R. Rocha (Texas Tech Univ. Burnett Center) in assisting with the conduct of this research are greatly appreciated. American Society of Animal Science
TI - Corn or sorghum wet distillers grains with solubles in combination with steam-flaked corn: In vitro fermentation and hydrogen sulfide production
JF - Journal of Animal Science
DO - 10.2527/jas.2009-2486
DA - 2010-07-01
UR - https://www.deepdyve.com/lp/oxford-university-press/corn-or-sorghum-wet-distillers-grains-with-solubles-in-combination-c9Tsf1FaHf
SP - 2425
EP - 2432
VL - 88
IS - 7
DP - DeepDyve
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