ABSTRACT:The ethanol industry is expanding rapidly. This expansion in production of renewable energy also increases production of by-products. These byproducts, primarily distillers grains plus solubles (DGS), are utilized very efficiently by ruminants. When the starch in corn is fermented to produce ethanol, the remaining nutrients (protein, fat, fiber) are concentrated about 3-fold. Whereas DGS is an excellent protein source for ruminants, the large supply and the price relative to corn make DGS an attractive energy source as well. This is especially important with reduced availability and higher price of corn because of demand by the ethanol industry. A meta-analysis of 9 experiments, where various levels of wet DGS were fed to feedlot cattle, shows that wet DGS produced higher ADG and G:F compared with cattle fed corn-based diets

SummaryCorn-ethanol production is expanding rapidly with the adoption of improved technologies to increase energy efficiency and profitability in crop production, ethanol conversion, and coproduct use. Life cycle assessment can evaluate the impact of these changes on environmental performance metrics. To this end, we analyzed the life cycles of corn-ethanol systems accounting for the majority of U.S. capacity to estimate greenhouse gas (GHG) emissions and energy efficiencies on the basis of updated values for crop management and yields, biorefinery operation, and coproduct utilization. Directeffect GHG emissions were estimated to be equivalent to a 48% to 59% reduction compared to gasoline, a twofold to threefold greater reduction than reported in previous studies. Ethanol-to-petroleum output/input ratios ranged from 10:1 to 13:1 but could be increased to 19:1 if farmers adopted high-yield progressive crop and soil management practices. An advanced closed-loop biorefinery with anaerobic digestion reduced GHG emissions by 67% and increased the net energy ratio to 2.2, from 1.5 to 1.8 for the most common systems. Such improved technologies have the potential to move corn-ethanol closer to the hypothetical performance of cellulosic biofuels. Likewise, the larger GHG reductions estimated in this study allow a greater buffer for inclusion of indirect-effect land-use change emissions while still meeting regulatory GHG reduction targets. These results suggest that corn-ethanol systems have substantially greater potential to mitigate GHG emissions and reduce dependence on imported petroleum for transportation fuels than reported previously.

Cattle are an important reservoir of Escherichia coli O157:H7 leading to contamination of food and water, and subsequent human disease. This pathogen colonizes its hosts by producing several proteins such as Tir and EspA that are secreted by a type III secretion system. These proteins play a role in colonization of the intestine, suggesting that they might be useful targets for the development of a vaccine to reduce levels of this organism in cattle. Vaccination of cattle with proteins secreted by E. coli O157:H7 significantly reduced the numbers of bacteria shed in feces, the numbers of animals that shed, and the duration of shedding in an experimental challenge model. Vaccination of cattle also significantly (P=0.04) reduced the prevalence of E. coli O157:H7 in a clinical trial conducted in a typical feedlot setting. This strategy suggests it is possible to vaccinate cattle to decrease the level of E. coli O157:H7 shedding for the purpose of reducing the risk of human disease.

A feedlot (Exp. 1) experiment was conducted to evaluate the effects of an essential oil mixture (EOM), experimental essential oil mixture (EXP), tylosin, and monensin (MON) on performance, carcass characteristics, and liver abscesses. A metabolism experiment (Exp. 2) was conducted to evaluate the effects of EOM, EXP, and MON on ruminal fermentation and digestibility in finishing steers. In Exp. 1, 468 yearling steers (398 ± 34 kg initial BW) were used in 50 pens (10 pens/treatment) and received their respective dietary treatments for 115 d. Five dietary treatments were compared in Exp. 1: 1) control, no additives (CON); 2) EOM, 1.0 g/steer daily; 3) EXP, 1.0 g/steer daily; 4) EOM, 1.0 g/steer daily plus tylosin, 90 mg/ steer daily (EOM+T); and 5) monensin, 300 mg/steer daily plus tylosin, 90 mg/steer daily (MON+T). Compared with CON, steers fed MON+T had decreased DMI (P < 0.01), and steers fed EOM+T and MON+T had improved G:F (P ≤ 0.02). Average daily gain was not different among treatments (P > 0.58). There was a trend (P = 0.09) for a treatment effect on 12th-rib fat thickness, which resulted in a significant increase in calculated yield grade for the EOM+T treatment. No other carcass characteristics were affected by treatment (P ≥ 0.10). Prevalence of total liver abscesses was reduced for steers fed tylosin compared with no tylosin (P < 0.05). In Exp. 2, 8 ruminally fistulated steers (399 ± 49 kg initial BW) were assigned randomly to 1 of 4 treatments in a replicated 4 × 4 Latin square designed experiment. Treatments were 1) CON, 2) EOM, 3) EXP, and 4) MON with feeding rates similar to Exp. 1. There were no differences in DMI, OM intake, and apparent total tract DM or OM digestibilities among treatments (P > 0.30). Feed intake patterns were similar among feed additive treatments (P > 0.13). Total VFA (P = 0.10) and acetate (P = 0.06) concentrations tended to be affected by treatment with EOM numerically greater than CON. Average ruminal pH ranged from 5.59 to 5.72 and did not differ among treatments. Addition of a EOM or monensin to a diet containing tylosin improves G:F, but little difference was observed in metabolism or digestibility.

Two experiments were conducted to determine the effect of corn processing method and corn wet distillers grains plus solubles (WDGS) level on steer performance and metabolism. In Exp. 1, 480 crossbred steer calves (314 +/- 18 kg of BW) were used in a finishing experiment with a randomized complete block design and a 3 x 4 treatment structure. Diets were based on dry-rolled (DRC), high-moisture (HMC), or steam-flaked corn (SFC) with increasing levels of WDGS (0, 15, 27.5, or 40%; DM basis). A corn processing x WDGS level interaction (P < 0.01) was observed for ADG and G:F. Average daily gain and G:F increased linearly (P < 0.01) in steers fed DRC; ADG increased quadratically (P = 0.04) and G:F increased linearly (P = 0.02) in steers fed HMC; and ADG decreased quadratically (P = 0.02) with no change in G:F (P = 0.52) in steers fed SFC as WDGS increased. In Exp. 2, 7 ruminally fistulated steers (440 +/- 41 kg of BW) were used in a 6-period crossover design with 3 x 2 factorial treatment structure. Diets were the same as those fed in Exp. 1, except they contained only 2 levels of WDGS (0 or 40% of diet DM). Total tract starch digestibility was greater (P < 0.01) for steers fed SFC than for steers fed DRC or HMC. Minimum ruminal pH was less (P < 0.01) for steers fed SFC than for steers fed HMC or DRC. Variance of ruminal pH was different among all 3 processing methods with DRC < HMC < SFC (P < 0.10). In situ 22-h DM digestibility of DRC and HMC and starch digestibility of DRC were greater (P < 0.10) in steers fed DRC compared with steers fed HMC or SFC. Steers fed 0% WDGS had less (P < or = 0.02) intake of DM, OM, NDF, and ether extract compared with steers fed 40% WDGS. Total tract digestibility of DM and OM was greater (P < or = 0.08) and digestibility of ether extract tended (P = 0.11) to be less for steers fed 0% WDGS compared with steers fed 40% WDGS. Maximum ruminal pH and pH variance were greater (P < or = 0.08) in steers fed 0% WDGS. A corn processing x WDGS level interaction (P = 0.09) was observed for ruminal acetate to propionate ratio (A:P). Within diets containing 0% WDGS, A:P in steers fed SFC was less (P < or = 0.08). In diets containing 40% WDGS, A:P was similar between processing methods and not different from the SFC with 0% WDGS. The corn processing x WDGS level interaction observed in the finishing experiment may be due to the decreased ruminal A:P in DRC and HMC diets with 40% WDGS.