Corn or sorghum wet distillers grains with solubles in combination with steam-flaked corn: in vitro fermentation and hydrogen sulfide production

Effect of inclusion of distillers grains with solubles and crude glycerin in beef cattle finishing diets on ruminal fermentation and fatty acid biohydrogenation

An experiment was conducted to evaluate the impact of feeding bio-fuel co-products on ruminal fermentation characteristics and composition of omasal digesta flow. Four ruminally cannulated Holstein steers (371 ± 5 kg) were used in a 4 × 4 Latin Square design. Omasal sample collection and triple marker technique was used to quantify fatty acid omasal flow. Treatments were applied as a 2 × 2 factorial where a steam flaked corn (SFC) basal diet (DGS-N CG-N) was replaced with 40% of diet DM as corn distillers grains (DGS; DGS-Y CG-N) or 10% of diet DM as crude glycerin (DGS-N CG-Y) or 40% of diet DM distillers grains and 10% of diet DM as crude glycerin (DGS-Y CG-Y). No effects were observed for the interaction of DGS and glycerin on measured rumen characteristics. Dietary inclusion of glycerin decreased (P = 0.05) ruminal content 4-h post feeding on a DM basis but did not influence DMI (P = 0.64). Feeding DGS had no effect (P = 0.34) on particulate passage to the omasum (kg/d) in spite of greater (P = 0.04) DMI. Feeding DGS reduced flow rate (% of rumen volume/h) (P = 0.05) but did not affect total VFA concentration (P = 0.46) or average ruminal pH (P = 0.72). No differences (P > 0.05) were observed in ruminal parameters when feeding glycerin, besides ruminal particulate content (kg) on DM basis (P = 0.05). An interaction of DGS and glycerin affected intake of stearic (P < 0.01), linoleic (P < 0.01), and linolenic acid (P < 0.01). An interaction of DGS and glycerin did not affect individual fatty acid flow with respect to intake for stearic (P = 0.17), linoleic (P = 0.18), or linolenic acid (P = 0.66). Dietary inclusion of glycerin had no impact on g of linolenic (P = 0.16) or linoleic (P = 0.32) acid transformed. A trend was identified for cattle fed diets with glycerin to have increased (P = 0.07) grams of conjugated linoleic acid (CLA; C18:2 cis-9, trans-11) per gram of linoleic acid intake, with no impact on the percent of saturated fat (P = 0.44) or unsaturated fat (P = 0.43) in omasal flow. For cattle fed diets with DGS, fewer grams of linoleic (P < 0.01) and linolenic (P < 0.01) were present in digesta flow per gram of intake. Inclusion of DGS in the treatment diets also increased (P < 0.01) stearic acid flow (g) and CLA flow (g) per gram of stearic and linoleic acid intake, respectively. Observed differences in CLA proportion post fermentation may indicate interrupted biohydrogenation when glycerin is fed.

Production of Hydrogen Sulfide by Fermentation in Rumen and Its Impact on Health and Production of Animals

Hydrogen sulfide is a Janus-faced molecule with many beneficial and toxic effects on the animal health. In ruminants, rumen fermentation plays a vital role in the digestion and absorption of nutrients. During rumen fermentation, the production of hydrogen sulfide can occur, and it can be rapidly absorbed into the body of the animals through the intestinal wall. If the production of hydrogen sulfide concentration is higher in the rumen, it can cause a toxic effect on ruminants known as poliomyelitis. The production of hydrogen sulfide depends on the population of sulfate-reducing bacteria in the rumen. In rodents, H2S maintains the normal physiology of the gastrointestinal tract and also improves the healing of the chronic gastric ulcer. In the gut, H2S regulates physiological functions such as inflammation, ischemia–reperfusion injury and motility. In this review article, we summarize the toxicity occurrence in the body of animals due to high levels of hydrogen sulfide production and also recent progress in the studies of physiological function of H2S in the gut, with a special emphasis on bacteria-derived H2S is discussed in this review.

Energy costs of feeding excess protein from corn-based by-products to finishing cattle

The increased use of by-products in finishing diets for cattle leads to diets that contain greater concentrations of crude protein (CP) and metabolizable protein (MP) than required. The hypothesis was that excess dietary CP and MP would increase maintenance energy requirements because of the energy costs of removing excess N as urea in urine. To evaluate the potential efficiency lost, two experiments were performed to determine the effects of feeding excess CP and MP to calves fed a finishing diet at 1 × maintenance energy intake (Exp. 1) and at 2 × maintenance intake (Exp. 2). In each experiment, eight crossbred Angus-based steers were assigned to two dietary treatments in a switchback design with three periods. Treatments were steam-flaked corn-based finishing diets with two dietary protein concentrations, 13.8% CP/9.63% MP (CON) or 19.5% CP/14.14% MP (dry matter basis; ECP), containing corn gluten meal to reflect a diet with excess CP and MP from corn by-products. Each period was 27 d in length with a 19-d dietary adaptation period in outdoor individual pens followed by a 4-d sample collection in one of four open circuit respiration chambers, 2-d fast in outdoor pen, and 2-d fast in one of four respiration chambers. Energy metabolism, diet digestibility, carbon (C) and nitrogen (N) balance, oxygen consumption, and carbon dioxide and methane production were measured. At both levels of intake, digestible energy as a proportion of gross energy (GE) tended to be greater (P < 0.06) in ECP than in CON steers. Metabolizable energy (ME) as a proportion of GE tended to be greater (P = 0.08) in the ECP steers than in the CON steers at 2 × maintenance intake. At 1 × and 2 × maintenance intake, urinary N excretion (g/d) was greater (P < 0.01) in the ECP steers than the CON steers. Heat production as a proportion of ME intake at 1 × maintenance tended (P = 0.06) to be greater for CON than for ECP (90.9% vs. 87.0% for CON and ECP, respectively); however, at 2 × maintenance energy intake, it was not different (63.9% vs. 63.8%, respectively). At 1 × maintenance intake, fasting heat production (FHP) was similar (P = 0.45) for both treatments, whereas at 2 × maintenance intake, FHP tended to be greater (P = 0.09) by 6% in ECP than in CON steers. Maintenance energy requirements estimated from linear and quadratic regression of energy retention on ME intake were 4% to 6% greater for ECP than for CON. Results of these studies suggest that feeding excess CP and MP from a protein source that is high in ruminally undegradable protein and low in protein quality will increase maintenance energy requirements of finishing steers.

Utilization of canola and sunflower meals as replacements for soybean meal in a corn silage-based stocker system1

Two experiments were conducted to evaluate 3 silage-based stocker diets. In Exp. 1, diets were fed to a total of 276 animals over a period of 3 yr and performance data was collected. In Exp. 2, the same diets were subjected to in vitro digestion for 5 time periods: 0, 6, 12, 24, and 48 h, to evaluate IVDMD, production of fermentation end products, and efficiency of transformation of energy. The experimental diets were similar, except for their protein supplements. They were composed of: 1) 74% corn silage, 15.2% ground ear corn, and 10.8% soybean meal (SBM); 2) 74.4% corn silage, 9.8% ground ear corn, and 15.8% canola meal (CAN); 3) 74.5% corn silage, 9.8% ground ear corn, and 15.7% sunflower meal (SUN). Results from Exp. 1 showed that DMI was similar across all treatments (P = 0.167), but ADG was greater (P = 0.007) for animals fed either SBM or CAN than for animals fed SUN (1.29, 1.28, and 1.20 kg/d, respectively). Both CAN and SUN significantly reduced (P < 0.001) daily feeding cost per animal in comparison to SBM. Exp. 2 revealed that total VFA production was similar for all treatments (P = 0.185), and greatest molar proportions of propionate were observed for SBM and CAN (P = 0.02). Additionally, IVDMD was highest for SBM (P < 0.001). Regression analysis showed that most of the evaluated traits followed a quadratic trend for incubation times (P ≤ 0.02). On average, the in vitro technique used in this study was able to account for 97.03% of the caloric transformations suffered by DE throughout the different incubation times. Overall, our findings revealed that although animals receiving SUN had the cheapest daily feeding cost, important traits like ADG and feed conversion rate were negatively affected by this treatment. In contrast, data showed that CAN was an effective replacement for SBM for it maintained similar animal performance while decreasing feed costs. Therefore, from a producer standpoint, CAN is a viable alternative to replace the more costly SBM diet in silage-based stocker operations.

Effects of dietary roughage and sulfur in diets containing corn dried distillers grains with solubles on hydrogen sulfide production and fermentation by rumen microbes in vitro

Dried distillers grains with solubles (DDGS) have been used in production animal diets; however, overuse of DDGS can cause toxic concentrations of ruminal hydrogen sulfide gas (HS), resulting in polioencephalomalacia, a deleterious brain disease. Because HS gas requires an acidic rumen environment and diet can influence ruminal pH, it has been postulated that dietary manipulation could help mitigate HS production. The objective of this study was to assess the effect of dietary roughage and sulfur concentrations on HS production and rumen fermentation. In Exp. 1, 7 dual-flow continuous culture fermenters were used in 4 consecutive 9-d periods consisting of 6 d of adaptation followed by 3 d of sampling. At the conclusion of each 9-d continuous culture period, adapted rumen fluid was used for inoculation of 24-h batch culture incubations for Exp. 2. For both experiments, 6 dietary treatments were formulated to consist of 0.3%, 0.4%, or 0.5% dietary sulfur (LS, MS, and HS, respectively) and 3% or 9% dietary roughage (LR and MR, respectively), using grass hay as the roughage source. A corn-based diet without DDGS was used as a control diet. Headspace gas was sampled to determine HS production and concentration. In Exp. 1, greater dietary roughage had no effect ( = 0.14) on HS production but did create a less acidic environment because of an increase ( < 0.01) in the in vitro pH. In Exp. 2, an increase in dietary sulfur caused an increase ( = 0.04) in ruminal HS production, but there was no direct effect ( = 0.25) of dietary roughage on HS production. Greater dietary roughage resulted in a less ( = 0.01) acidic final batch culture pH but a lower ( < 0.01) total VFA concentration. Further investigation is needed to determine a more effective way to mitigate ruminal HS production using dietary manipulation, which could include greater inclusion of dietary roughage or the use of different roughage sources.

Effects of dry-rolled or high-moisture corn with twenty-five or forty-five percent wet distillers' grains with solubles on energy metabolism, nutrient digestibility, and macromineral balance in finishing beef steers

The effects of feeding a dry-rolled corn-based diet (DRCB) or a combination of a high-moisture corn-based diet (HMCB) with dry-rolled corn (DRC; 2:1 ratio of high-moisture corn [HMC] and DRC) with 25 and 45% wet distillers' grains with solubles (WDGS) on energy metabolism and nutrient and mineral balance were evaluated in 8 finishing steers using a replicated Latin square design. The model included the fixed effects of dietary treatment, the WDGS × diet type interaction, and period and the random effects of square and steer within square were also included. Treatments consisted of a DRCB with 25% WDGS, a DRCB with 45% WDGS, a combination of HMCB and DRC with 25% WDGS, and a combination of HMCB and DRC with 45% WDGS. Cattle consuming DRCB consumed a greater amount of DM ( < 0.01) and GE intake was also greater when feeding DRCB with 25% WDGS than when feeding DRCB with 45% WDGS ( < 0.01). As a proportion of GE intake, cattle consuming HMCB had a greater fecal energy loss ( = 0.01). Digestible energy loss as a proportion of GE intake was greater when cattle were fed DRCB than when cattle were fed HMCB ( = 0.01) and when WDGS was included at 45% of DM ( = 0.05). As a proportion of GE intake, cattle consuming DRCB and 25% WDGS respired a greater amount of methane (Mcal) than cattle consuming 45% WDGS. As a proportion of GE intake, ME was greater in DRCB than in HMCB ( = 0.01). Within HMCB, 45% WDGS had more megacalories of retained energy than 25% WDGS. Nitrogen excretion (g) was greater in the urine ( < 0.01) and feces ( < 0.05) when 45% WDGS was included. As a proportion of N intake, total N retained was greater when a greater amount of WDGS was included in the diet ( = 0.05). Digestibility was greater in DRCB than in HMCB ( = 0.02). Starch intake, excretion, and digestibility as a proportion of intake were greater in DRCB than in HMCB ( < 0.01) and when WDGS was included at 25% than when WDGS was included at 45% of the diet ( < 0.01). Intake of ether extract was greater in HMCB when 45% WDGS was included ( < 0.01), and fecal excretion was greater in diets including 25% WDGS than in diets including 45% WDGS ( = 0.02). Sulfur intake was greater as the inclusion of WDGS increased from 25 to 45% ( < 0.01). We interpret that if the basal concentrate portion of the diet is based on HMC, adding an increased amount of WDGS can improve retained energy, and within DRCB, more energy is retained as fat and carbohydrate when cattle were fed 25% WDGS.

Effects of wet corn distillers grains with solubles on visceral organ mass, trace mineral status, and polioencephalomalacia biomarkers of individually-fed cattle

Twenty-four steers (initial BW = 385 ± 1.1 kg) were blocked by BW and randomly assigned to 3 dietary treatments (0, 30, or 60% wet distillers grains with solubles [WDGS]; DM basis) and were fed individually to determine the effect of WDGS on live growth and carcass performance, visceral organ mass, trace mineral status, and polioencephalomalacia biomarkers. Steers were slaughtered at 125, 150, 164, and 192 d (2 blocks/slaughter date) when external fat depth was approximately 1.3 cm based on visual appraisal. Steers fed 30% WDGS had greater DMI than those fed 0 or 60% WDGS (P < 0.05), and steers fed 60% WDGS had the lowest carcass-adjusted ADG (P < 0.09) of the 3 treatments. Nonetheless, WDGS concentration did not alter feed efficiency (P > 0.41) on either live or carcass-adjusted basis. Steers fed 30% WDGS had greater liver S and Mn concentrations (DM basis) and lower liver Fe concentrations than control steers (P < 0.10; initial values used as a covariate), and feeding 60% WDGS decreased liver Cu and increased liver Fe (P < 0.10) compared with feeding 30% WDGS. Cytochrome c oxidase (COX) activity in brain tissue tended to be decreased with 60 vs. 30% WDGS (P = 0.12), and COX activity decreased linearly (P = 0.06) in lung tissue as dietary WDGS concentration increased. Likewise, gut fill linearly increased (P = 0.01) with increasing WDGS concentration. Feeding 30% WDGS increased fractional mass (g/kg of empty BW) of the small intestine (P < 0.10) compared with controls, whereas 60% WDGS increased fractional kidney mass (P < 0.10) compared with 30% WDGS. Overall, results suggest that gut fill, Cu status, and COX activity seem to be compromised by WDGS when fed at 60% of diet DM in diets based on steam-flaked corn, which suggests a greater susceptibility to polioencephalomalacia.

Effects of dietary concentration of wet distillers grains on performance by newly received beef cattle, in vitro gas production and volatile fatty acid concentrations, and in vitro dry matter disappearance

Three studies were designed to evaluate effects of wet distillers grains with solubles (WDGS) on health and performance of newly received beef cattle, in vitro gas production, molar proportions and total concentrations of VFA, and IVDMD. In Exp. 1 and 2, 219 (BW = 209 kg, SE = 2.2 kg; Exp. 1) and 200 beef steers (BW = 186 kg, SE = 3.2 kg; Exp. 2) were used in randomized complete block design receiving studies. The 4 dietary treatments (DM basis) were a 65% concentrate, steam-flaked corn (SFC)-based receiving diet without WDGS (CON) or diets that contained 12.5, 25.0, or 37.5% WDGS. There were no differences among the 4 receiving diets in BW (P ≥ 0.61), ADG (P ≥ 0.75), DMI (P ≥ 0.27), and G:F (P ≥ 0.35), or in the proportion of cattle treated for morbidity from bovine respiratory disease in either of the 2 experiments. In Exp. 3, in vitro methods were used to determine the effects of WDGS on IVDMD, total gas production, and molar proportions and total concentrations of VFA. Substrates used for the incubations contained the same major components as the diets used in Exp. 1, with ruminal fluid obtained from steers fed a 60% concentrate diet. Total gas production was less (P = 0.03) for the average of the 3 WDGS substrates than for CON, with a linear decrease (P = 0.01) in total gas production as WDGS concentration increased in the substrates. In contrast to gas production, IVDMD was greater for the average of the 3 WDGS concentrations vs. CON (P ≤ 0.05) at 6 and 12 h and increased (P ≤ 0.02) with increasing WDGS concentration at 6 (linear and quadratic) and 12 h (linear) of incubation. At 48 h, there was a quadratic effect (P = 0.05) on IVDMD, with the greatest value for 25% WDGS. Molar proportion of butyrate increased linearly (P < 0.01) as the concentration of WDGS increased in the substrate, and the average of the 3 substrates containing WDGS had a greater proportion of butyrate (P = 0.03) than CON. Performance data from Exp. 1 and 2 indicate that including WDGS in the SFC-based diets for newly received cattle can be an effective at concentrations up to 37.5% of the DM. In vivo measurements are needed to corroborate the in vitro fermentation changes noted with addition of WDGS.

Effects of increasing concentrations of wet distillers grains with solubles in steam-flaked, corn-based diets on energy metabolism, carbon-nitrogen balance, and methane emissions of cattle

The use of wet distillers grains with solubles (WDGS) in feedlot diets has increased in the Southern Great Plains as a result of the growing ethanol industry. Nutrient balance and respiration calorimetry research evaluating the use of steam-flaked corn (SFC)-based diets in conjunction with WDGS is limited. Therefore, the effects of increasing concentrations of WDGS in a SFC-based diet on energy metabolism, C, and N balance, and enteric methane (CH4) production was evaluated in Jersey steers fed at 2 times maintenance, using respiration calorimetry chambers. Four treatments were used in two 4 × 4 Latin square designs, using 8 steers. Treatments consisted of: 1) SFC-based diet with 0% WDGS (SFC-0); 2) SFC-based diet with 15% WDGS (SFC-15); 3) SFC-based diet with 30% WDGS (SFC-30); and 4) SFC-based diet with 45% WDGS (SFC-45). Diets were balanced for degradable intake protein (DIP) by adding cottonseed meal to the SFC-0 diet. As a proportion of GE, fecal, urinary, and CH4 energy increased linearly (P < 0.03) as WDGS concentration increased in the diet. In contrast, DE, ME, and retained energy decreased linearly (P < 0.01) as a proportion of GE as WDGS concentration increased. Increasing concentration of WDGS in the diet did not affect (P > 0.78) heat production as a proportion of GE. As a result of greater N intake, total N excretion increased linearly (P < 0.01) with increasing WDGS inclusion in the diet. Fecal C loss and CH4-C respired increased linearly (P < 0.01) when WDGS concentration increased in the diet whereas CO2-C respired decreased (linear, P = 0.05) as WDGS concentration increased. We conclude that CH4 production as a proportion of GE increases linearly (P < 0.01) when WDGS concentration in the diet is increased; however, dietary inclusion of WDGS at up to 45% seems to have no effect (P > 0.78) on heat production as a proportion of GE. The reason for a linear decrease in retained energy as WDGS increased was likely because of increased fecal energy loss associated with feeding WDGS. Total N excretion, fecal C loss, and CH4-C respired increased linearly with increasing concentration of WDGS in the diet. We determined NEg values for WDGS to be 2.02, 1.61, and 1.38 Mcal/kg when included at 15%, 30%, and 45%, respectively, in a SFC-based diet. From these results we conclude that the energy value (NEg) of WDGS in a finishing cattle diet based on SFC must be decreased as the inclusion increases.

Effects of corn processing method and dietary inclusion of corn wet distillers grains with solubles on odor and gas production in cattle manure

The growing ethanol industry in the Southern Great Plains has recently increased the use of wet distillers grains with solubles (WDGS) in beef cattle finishing diets. Two experiments were conducted to evaluate odorous compound production in urine and feces of feedlot steers fed diets with different concentrations of WDGS and different grain processing methods. In both experiments, a Latin square design was used. In Exp. 1, a 2× 2 factorial arrangement of treatments was used and the factors consisted of corn processing method [steam-flaked corn (SFC) or dry-rolled corn (DRC)] and inclusion of corn-based WDGS (0 or 30% on a DM basis). Thus, the 4 treatment combinations consisted of: 1) SFC-based diet with 0% WDGS (SFC-0); 2) SFC-based diet with 30% WDGS (SFC-30); 3) DRC-based diet with 0% WDGS (DRC-0); and 4) DRC-based diet with 30% WDGS (DRC-30). In Exp. 2, all diets were based on SFC and the 4 treatments consisted of: 1) 0% WDGS (SFC-0); 2) 15% WDGS (SFC-15); 3) 30% WDGS (SFC-30); and 4) 45% WDGS (SFC-45). In both experiments, diets were balanced for degradable intake protein and ether extract by the addition of cottonseed meal and fat. Fecal slurries were prepared from a 5-d composite of urine and feces collected from each treatment. The slurries were analyzed using a gas chromatograph for VFA, phenol, p-cresol, indole, skatole, hydrogen, methane (CH(4),) and total gas production. In Exp. 1, the DRC fecal slurries had greater initial total VFA concentration compared with the SFC-based slurries and accumulated a greater concentration of total gas throughout the incubation; however, the SFC-based manure resulted in more CH(4) production. In Exp. 2, total VFA concentrations did not differ across all fecal slurries initially and on d 28; however, throughout the incubation, slurries with 0 and 15% WDGS had the greatest total VFA concentration. Overall, the presence of starch in the feces was likely the determining factor for the accumulation of odorous compounds in the fecal slurries initially, which was especially evident in diets including DRC, and once methanogenic microorganisms were established they likely converted VFA to CH(4).

Effects of corn processing method and dietary inclusion of wet distillers grains with solubles on energy metabolism, carbon-nitrogen balance, and methane emissions of cattle

The growing ethanol industry in the Southern Great Plains has increased the use of wet distillers grains with solubles (WDGS) in beef cattle (Bos taurus) finishing diets. Few studies have used steam-flaked corn (Zea mays L.; SFC)-based diets to evaluate the effects of WDGS in finishing cattle diets, and a reliable estimate of the net energy value of WDGS has yet to be determined. Effects of corn processing method and WDGS on energy metabolism, C and N balance, and enteric methane (CH(4)) production were evaluated in a short-term study using 8 Jersey steers and respiration calorimetry chambers. A 2 by 2 factorial arrangement of treatments was used in a Latin square design. The 4 treatment combinations consisted of: i) SFC-based diet with 0% WDGS (SFC-0); ii) SFC-based diet with 30% WDGS (SFC-30); iii) dry-rolled corn (DRC)-based diet with 0% WDGS (DRC-0); and iv) DRC-based diet with 30% WDGS (DRC-30). Diets were balanced for degradable intake protein (DIP) and ether extract (EE) by the addition of cottonseed (Gossypium hirsutum L.) meal and yellow grease. As a proportion of GE, grain processing method did not affect (P ≥ 0.12) fecal, digestible, urinary, and ME, or heat production. Steers consuming SFC-based diets produced less (P < 0.04) CH(4) than steers consuming DRC-based diets. Retained energy tended to be greater (P = 0.09) for cattle consuming SFC- than DRC-based diets. Inclusion of WDGS did not affect (P ≥ 0.17) fecal, digestible, urinary, metabolizable, and retained energy, or heat production as a proportion of GE. Furthermore, neither inclusion of WDGS or grain processing method affected (P ≥ 0.17) daily CO(2) production. Due in part to greater N intake, cattle consuming diets containing 30% WDGS excreted more (P = 0.01) total N and excreted a greater (P < 0.01) quantity of N in the urine. From these results, we conclude that cattle consuming SFC-based diets produce less CH(4) and retain more energy than cattle fed DRC-based diets; however, dietary inclusion of WDGS at 30% seems to have little effect on CH(4) production and energy metabolism when diets are balanced for DIP and EE. Cattle excrete a greater amount of C when fed DRC compared with SFC-based diets, and dietary inclusion of 30% WDGS increases urinary N excretion. Finally, we determined the NE(g) values for WDGS were 1.66 and 1.65 Mcal/kg in a SFC or DRC-based diet, respectively, when WDGS replaced 30% of our control (SFC-0 and DRC-0) diets.

Effects of roughage concentration in steam-flaked corn-based diets containing wet distillers grains with solubles on feedlot cattle performance, carcass characteristics, and in vitro fermentation

Two studies were conducted to evaluate effects of wet distillers grains with solubles (WDG) and dietary concentration of alfalfa hay (AH) on performance of finishing beef cattle and in vitro fermentation. In both studies, 7 treatments were arranged in a 2 × 3 + 1 factorial; factors were dietary concentrations (DM basis) of WDG (15 or 30%) and AH (7.5, 10, or 12.5%) plus a non-WDG control diet that contained 10% AH. In Exp. 1, 224 beef steers were used in a randomized complete block (initial BW 342 kg ± 9.03) finishing trial. No WDG × AH interactions were observed (P > 0.12). There were no differences among treatments in final shrunk BW or ADG (P > 0.15), and DMI did not differ with WDG concentration for the overall feeding period (P = 0.38). Increasing dietary AH concentration tended (P < 0.079) to linearly increase DMI, and linearly decreased (P < 0.05) G:F and calculated dietary NE(m) and NE(g) concentrations. Carcasses from cattle fed 15% WDG had greater yield grades (P = 0.014), with tendencies for greater 12th-rib fat (P = 0.054) and marbling score (P = 0.053) than those from cattle fed 30% WDG. There were no differences among treatments (P > 0.15) in HCW, dressing percent, LM area, KPH, proportions of cattle grading USDA Choice, and incidence of liver abscesses. In Exp. 2, ruminal fluid was collected from 2 ruminally cannulated Jersey steers adapted to a 60% concentrate diet to evaluate in vitro gas production kinetics, H(2)S production, IVDMD, and VFA. Relative to the control substrate, including WDG in substrates increased (P < 0.01) H(2)S production and decreased total gas production (P = 0.01) and rate of gas production (P = 0.03). Increasing substrate WDG from 15 to 30% increased (P < 0.05) H(2)S production and decreased (P < 0.001) total gas production, with a tendency (P = 0.073) to decrease IVDMD and fractional rate of gas production (P = 0.063). Treatments did not significantly affect (P > 0.09) molar proportions or total concentration of VFA. Results indicate that including 15 or 30% WDG in steam-flaked corn-based diets did not result in major changes in feedlot performance or carcass characteristics, but increasing AH concentration from 7.5 to 12.5% in diets containing WDG decreased G:F. Including WDG in substrates decreased rate and extent of gas production and increased H(2)S production. Changes in various measures of in vitro fermentation associated with AH concentrations were not large.