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Objectives The objective was to determine the effects of degree of steam flaking of corn (SFC) on performance of finishing cattle fed diets containing wet distillers grains with solubles (WDGS). Materials and Methods Crossbred steers (n = 214: initial BW = 357 ± 26.0 kg) and heifers (n = 121: initial BW = 323 ± 30.9 kg) were randomly assigned to 54 pens and 6 diets containing 0, 15, or 30% WDGS and corn steam flaked to either 321 or 270 g/L bulk density (25 or 21 lb/bu, respectively) in a 2 × 3 factorial arrangement. Results and Discussion There were no interactions between WDGS concentration and SFC bulk density for growth performance (P > 0.48), and growth performance was not influenced by the degree of steam flaking of corn (P > 0.29). Dry matter intake (P Implications and Applications Results suggest optimal performance is achieved in SFC-based finishing diets when WDGS is fed at 15% of DM and that increasing the degree of steam flaking of corn to less than 321 g/L does not improve cattle performance in diets containing WDGS.

Objective The objective was to develop an equation to indirectly predict the effect of feeding ExperiorTM (lubabegron; Elanco Animal Health, Greenfield, IN) on ammonia gas emissions (AGE) from cattle in subsequent feedlot studies. Materials and Methods Our approach was to develop a prediction equation [the Elanco Ammonia Gas Emission Prediction Model (EPM)] using data from a 91-d clinical efficacy study in which lubabegron was fed to cattle housed in a cattle pen enclosure system and compare the precision and accuracy of the EPM with the precision and accuracy of a published equation that was developed to predict AGE from open-air feedlots. Results and Discussion The evaluation of the published equation used to predict daily AGE (g/animal) resulted in poor precision (R2 = 0.329) but reasonable accuracy (prediction bias = +14.8%). The developed EPM equation explained 98.7% of the variation in observed log10 of cumulative AGE in the clinical efficacy study. Implications and Applications The EPM explained 58.9 to 84.9% of the variation in cumulative AGE in 2 evaluation data sets, with a prediction bias of +0.13 to +18.6%. These data suggest that the EPM derived from the development data set using the cattle pen enclosure measurement system showed great promise to accurately and precisely predict cumulative AGE in future feedlot studies.

The use of distiller’s grains (DG) in beef cattle finishing diets is a common practice. However, the effects of supplemental fat on performance and nutrient losses of cattle fed diets containing DG are not known. Therefore, we fed 398 crossbred yearling heifers (initial BW = 373.5 kg) for 106 d to determine the effects of dietary fat concentration and sorghum-based wet distiller’s grains with solubles (SWDGS) on performance, carcass characteristics, and nutrient losses of finishing cattle. Treatments included two 92% concentrate, steam-flaked corn (SFC)-based diets with 0% or 3% added fat from yellow grease and 3 SFC-based diets with 15% SWDGS (DM basis) that contained either 0%, 1.5%, or 3% added fat (8 pens per treatment) in a randomized block design. Overall DMI and ADG were 5% to 6% greater (P < 0.01) for heifers fed 15% SWDGS than for those fed 0% SWDGS. Among heifers fed 15% SWDGS, DMI was greatest (P = 0.04; quadratic effect) and ADG tended (P = 0.12; quadratic effect) to be greatest for heifers fed 1.5% fat. The ADG:DMI did not differ between 0% SWDGS with 0% or 3% fat, and was not altered by replacing a portion of SFC with SWDGS (P > 0.36). However, ADG:DMI tended to increase as more fat was added to diets with 15% SWDGS (P = 0.06). Average hot carcass weight (HCW) was 5 kg greater (P = 0.05) when SWDGS was fed, but HCW tended to be greatest for heifers fed 15% SWDGS with 1.5% fat (P = 0.09, quadratic effect). Heifers fed 0% SWDGS with 0% fat tended to have a lower marbling score, less rib fat, lower average yield grade (P < 0.08), and more (P < 0.01) yield grade 1 carcasses than heifers fed 0% SWDGS with 3% fat. Averaged across fat levels, heifers fed 15% SWDGS had more rib fat and a higher yield grade (P < 0.03) than heifers fed 0% SWDGS. Feeding 15% SWDGS did not alter carcass quality grade distribution compared to feeding 0% SWDGS, but 15% SWDGS produced fewer yield grade 3 carcasses (P = 0.03) than 0% SWDGS. The calculated NEg of SWDGS (1.36 Mcal/kg) was 91% of the tabular value for dry rolled corn (1.50 Mcal/kg) and 84% of the tabular value for SFC (1.62 Mcal/kg). Nitrogen intake, and N excretion were greater (P < 0.05) in heifers fed 15% SWDGS than in heifers fed the 0% SWDGS diets, but N loss as a % of N intake was less (P < 0.05). Our results suggest adding 1.5% fat to diets containing 15% SWDGS may improve beef cattle performance; however, feeding logistics need to be considered when pricing wet DG.

Nitrous oxide (N2O) is a greenhouse gas with a higher global warming potential than carbon dioxide (CO2) or methane (CH4). The objectives of this research were to quantify enteric N2O emissions from beef cattle and determine effects of dietary nitrate (NO3) concentrations. Experiments consisted of one in vitro incubation trial and 2 live animal (LA) trials. During the in vitro trial, gas was collected from 4 forage-based and 5 corn-based diets. During the LA trials, emissions were monitored from steers in respiration chambers. In LA trial 1, 5 measurements of 256 to 720 min were conducted on a single steer within a 48-h period. In LA trial 2, measurements were conducted on 4 steers in the absence of manure. Highest in vitro N2O production was from diets containing added NO3 or alfalfa. In vitro N2O increased with dietary NO3 concentrations (r2 = 0.99), with little correlation to dietary CP (r2 = 0.17). Added NO3 decreased CH4 emissions. Mean N2O emission rates (±SD) from the LA trials were 6.93 ± 2.99 mg of N2O∙kg−1 of DMI in trial 1 and 2.20 ± 0.10 mg of N2O∙kg−1 of DMI in trial 2. Mean enteric N2O emissions accounted for 0.35% (LA trial 1) and 0.12% (LA trial 2) of CO2 equivalents. Enteric N2O emission rates were 6 to 40 times lower than values cited in earlier publications. Enteric N2O emission rates were also 58 to 108 times lower than manure emissions. Therefore, efforts to reduce greenhouse gas emissions from beef cattle should focus on enteric CH4 and manure N2O as opposed to enteric N2O.

Wet distiller’s grains with solubles (WDGS) are a common by-product feedstuff generated by the grain–ethanol industry, and it is used extensively by the cattle feeding industry. Distillers grains are typically high in protein; however, the protein in WDGS has a low ruminal degradability, and thus may result in a deficiency of RDP in the diet even when dietary CP concentrations are high. Assessment of the RDP needs in diets containing WDGS is needed to aid the cattle feeding industry in managing feed costs and potential environmental issues. To that end, we conducted 2 feeding studies to evaluate the supplemental RDP requirements of beef cattle fed steam-flaked corn-based finishing diets. In Exp. 1, 525 yearling steers (initial body weight = 373 ± 13 kg) received treatments in a 2 × 3 + 1 factorial. Dietary factors included WDGS (15 or 30% of DM) and nonprotein N (NPN; 0, 1.5, or 3.0% of DM) from urea (0, 0.52, and 1.06%). The control diet without WDGS contained 3.0% NPN (1.06% urea) and cottonseed meal. Diets were formulated to have equal crude fat concentrations. Overall gain efficiency among steers fed 15% WDGS was greatest for 1.5% NPN and least for 0% NPN (P = 0.07, quadratic), whereas gain efficiency decreased linearly (P < 0.09) as NPN increased in the 30% WDGS diets. Dressing percent was greater (P < 0.01) for the Control diet than for 15 or 30% WDGS. In Exp. 2, 296 steer calves (initial BW = 344 ± 12 kg) were fed 1 of 4 experimental diets that included a Control diet without WDGS (contained 3% NPN from urea, and cottonseed meal) and 15% WDGS diets with either 1.50, 2.25, or 3.00% NPN (0.52, 0.78, and 1.04% urea, respectively, on a DM basis). Overall gain efficiency on either a live or carcass-adjusted basis was not different among treatments (P > 0.15). Dietary NPN concentration did not influence growth performance (P > 0.21). Increasing dietary WDGS concentration resulted in decreasing (P < 0.05) diet digestibility (determined with an internal marker) and increasing (P < 0.05) N volatilization losses (determined by diet and manure N:P ratio); however, the effects of NPN level on digestibility and N losses were somewhat inconsistent across experiments. Results suggest that optimum performance for cattle fed 15% WDGS occurred when the diet contained between 1.5 and 2.25% NPN. However, no supplemental NPN was needed to support optimum performance in diets containing 30% WDGS.

Research examining the nutrition of grazing ruminants can be a rewarding career; however, this type of science possesses great challenges. Grazing research requires the scientist to make many assumptions, deal with great variability across a landscape, and carefully plan and manage unknown effects and finally produce a published experiment that has applications across an extensive region. Probably the most rewarding aspect to researchers in this field is the ability to collaborate with researchers from other disciplines to evaluate the entire system. The knowledge that can be gained from studying a grazing system with collaborating scientists is valuable beyond a quantifiable number. Animal performance is a function of the soil–plant–animal–climate interaction with one factor affecting the other. One area of research that has been demonstrated in recent years has been that plant structure and mass will effect instantaneous intake rate and possibly total DMI. Struggles to predict DMI by grazing livestock have not been gifted with high predictive quality; the low prediction quality has probably resulted from minimal characterization of the sward and its integration in predictive models. Furthermore, grazing management affects the other ecological services provided by a landscape. Ecological services are often thought of as just wildlife habitat, but these services also include carbon sequestration, water infiltration and runoff, nutrient management, and food and fuel production for a growing world population. We know that ruminants are significant emitters of methane, and with the current level of interest in climate change, research examining the effects of grazing management on ecological services can possibly be as valuable to producers as animal performance data alone. The only way producers will adapt sustainable grazing systems is if these systems are as profitable as other opportunities for the same land resource. In the future, producers will need data showing the effects of their production systems on other ecological services. Visionary teams of agricultural scientists need to collect these ecological impact data in the present, because the public will be unwilling to wait decades for them to be collected in the future.

Sequential fractionation coupled with phosphatase hydrolysis allows a greater understanding of the effects of animal manure on the chemical distribution of soil P. Concentrations of specific soil P fractions were determined after long-term (>10 yr) poultry litter application at rates of 4.5, 6.7, 9.0, 11.2, and 13.4 Mg manure ha⁻¹ yr⁻¹ to watershed-scale plots (cultivated and grazed–ungrazed pasture) on a calcareous Texas Blackland Vertisol. Soil total extractable P (Pₜ) and inorganic P (Pᵢ) were quantified following sequential extraction with H₂O, NaHCO₃, NaOH, and HCl. Hydrolyzable organic P (Pₑ) and non-hydrolyzable organic P (Pₙₑ) were determined in the extracted fractions following enzymatic hydrolysis. Litter application increased Pₜ regardless of land-use type compared with the control. Concentrations of H₂O-extractable Pᵢ in litter-amended plots increased by 9 to 34% (cultivated) and 7 to 30% (pasture) over the control, indicating substantial risk of soluble P runoff. Labile organic P (Pₒ) extracted with H₂O and NaHCO₃ decreased in the order monoester > nucleic acid > phytate > Pₙₑ. An average of 68% of Pₜ was extractable with HCl. Organic P comprised the majority (95%) of HCl-Pₜ; however, only trace levels of HCl-Pₒ were hydrolyzable, and litter application increased HCl-Pₙₑ up to 217%. Thus, litter application increased levels of both soluble Pᵢ and stable Pₙₑ, but the specific response varied with application rate and land management. This study increased understanding of P chemical distribution with time in litter-amended soil with high clay and CaCO₃ contents under differing land-use scenarios.

Animal agriculture is a significant source of ammonia (NH3). Cattle excrete most ingested nitrogen (N); most urinary N is converted to NH3, volatilized and lost to the atmosphere. Open lot dairies on the southern High Plains are a growing industry and face environmental challenges as well as reporting requirements for NH3 emissions. We quantified NH3 emissions from the open lot and wastewater lagoons of a commercial New Mexico dairy during a nine-day summer campaign. The 3500-cow dairy consisted of open lot, manure-surfaced corrals (22.5 ha area). Lactating cows comprised 80% of the herd. A flush system using recycled wastewater intermittently removed manure from feeding alleys to three lagoons (1.8 ha area). Open path lasers measured atmospheric NH3 concentration, sonic anemometers characterized turbulence, and inverse dispersion analysis was used to quantify emissions. Ammonia fluxes (15-min) averaged 56 and 37 μg m−2 s−1 at the open lot and lagoons, respectively. Ammonia emission rate averaged 1061 kg d−1 at the open lot and 59 kg d−1 at the lagoons; 95% of NH3 was emitted from the open lot. The per capita emission rate of NH3 was 304 g cow−1 d−1 from the open lot (41% of N intake) and 17 g cow−1 d−1 from lagoons (2% of N intake). Daily N input at the dairy was 2139 kg d−1, with 43, 36, 19 and 2% of the N partitioned to NH3 emission, manure/lagoons, milk, and cows, respectively.

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.

Enteric methane (CH) production attributable to beef cattle contributes to global greenhouse gas emissions. Reliably estimating this contribution requires extensive CH emission data from beef cattle under different management conditions worldwide. The objectives were to: 1) predict CH production (g d animal), yield [g (kg dry matter intake; DMI)] and intensity [g (kg average daily gain)] using an intercontinental database (data from Europe, North America, Brazil, Australia and South Korea); 2) assess the impact of geographic region, and of higher- and lower-forage diets. Linear models were developed by incrementally adding covariates. A K-fold cross-validation indicated that a CH production equation using only DMI that was fitted to all available data had a root mean square prediction error (RMSPE; % of observed mean) of 31.2%. Subsets containing data with ≥25% and ≤18% dietary forage contents had an RMSPE of 30.8 and 34.2%, with the all-data CH production equation, whereas these errors decreased to 29.3 and 28.4%, respectively, when using CH prediction equations fitted to these subsets. The RMSPE of the ≥25% forage subset further decreased to 24.7% when using multiple regression. Europe- and North America-specific subsets predicted by the best performing ≥25% forage multiple regression equation had RMSPE of 24.5 and 20.4%, whereas these errors were 24.5 and 20.0% with region-specific equations, respectively. The developed equations had less RMSPE than extant equations evaluated for all data (22.5 vs. 23.2%), for higher-forage (21.2 vs. 23.1%), but not for the lower-forage subsets (28.4 vs. 27.9%). Splitting the dataset by forage content did not improve CH yield or intensity predictions. Predicting beef cattle CH production using energy conversion factors, as applied by the Intergovernmental Panel on Climate Change, indicated that adequate forage content-based and region-specific energy conversion factors improve prediction accuracy and are preferred in national or global inventories., Authors gratefully acknowledge project funding from the USDA National Institute of Food and Agriculture Federal Appropriations under Project PEN 04539 and Accession number 1000803; the Joint Programming Initiative on Agriculture, Food Security and Climate Change (FACCE-JPI)’s ‘GLOBAL NETWORK’ project and the ‘Feeding and Nutrition Network’ (http://animalscience.psu.edu/fnn) of the Livestock Research Group within the Global Research Alliance for Agricultural Greenhouse Gases (www.globalresearchalliance.org); the Sesnon Endowed Chair program (UC Davis); the Swiss Federal Office of Agriculture, Berne, Switzerland; AHDB Beef and Lamb, the Scottish Government, Defra and the devolved administrations through the UK Agricultural Greenhouse Gas Inventory Research Platform; French National Research Agency through the FACCE-JPI program (ANR-13-JFAC-0003-01); the Cooperative Research Program for Agriculture Science, (Project No. PJ013448012018), RDA, Republic of Korea; the Australian Government Department of Agriculture, Fisheries and Forestry (Carbon Farming Futures Action on the Ground program; AOTGR2-0400); the financial support of the Reducing Emissions from Livestock Research Program, the National Livestock Methane Program, Meat and Livestock Australia, CSIRO and Ridley AgriProducts Pty, Ltd; the Institute of Science and Technology in Animal Science (INCTCA 465377/2014-9), the Department of Agriculture, Food and the Marine (DAFM), Ireland (AGRI-I project); European Commission through SMEthane (FP7‐SME‐262,270); Beef Cattle Research Council of the Canadian Cattlemen’s Association; the Cofund for Monitoring & Mitigation of Greenhouse Gases from Agri- and Silvi-culture (FACCE ERA-GAS)’s project Capturing Effects of Diet on Emissions from Ruminant Systems and the Dutch Ministry of Agriculture, Nature and Food Quality (AF-EU-18010 & BO-4400159-01).

HighlightsEnteric methane (CH4) from beef cows on pasture was measured over three seasons using three methods.Methods yielded similar results during the summer grazing season but diverged in autumn and winter seasons.Emission averaged 0.34, 0.27, and 0.29 kg CH4 cow-1 during lactation, mid-gestation, and late gestation, respectively.Annualized enteric methane emission rate for a beef cow herd grazing tallgrass prairie was 0.32 kg d-1 cow-1.Abstract. Methane (CH4) is an important greenhouse gas, and about 20% of the carbon dioxide equivalent (CO2e) greenhouse gases emitted by U.S. agriculture are attributed to enteric CH4 produced by grazing beef cattle. Grazing cattle are mobile point sources of methane and present challenges to quantifying the enteric methane emission rate (MER). In this study, we applied three methods to measure herd-scale and individual-animal MER for a herd of beef cows grazing a native tallgrass prairie: a point source method that used forward-mode dispersion analysis and open-path lasers and cow locations, an open chamber breath analysis system (GreenFeed), and an eddy covariance ratio method that used the ratio of CH4 and CO2 mass fluxes. Three campaigns were conducted during the early season (July), late season (October), and dormant season (February). The point source and GreenFeed methods yielded similar MER (±SD) values during the early season campaign: 0.38 ±0.04 and 0.34 ±0.05 kg d-1 cow-1, respectively. However, the MER values from the two methods diverged in subsequent seasons. The GreenFeed MER decreased through the late and dormant seasons to 0.23 ±0.03 and 0.19 ±0.03 kg d-1 cow-1, respectively. In contrast, the point source MER stayed the same during the late season and increased during the dormant season to 0.41 ±0.07 kg d-1 cow-1. The CH4:CO2 ratio method, which was used only during the dormant season, yielded a MER of 0.29 ±0.05 kg d-1 cow-1. The point source and GreenFeed methods measured different MER (integrated herd-scale versus a subset of individual animals) and likely sampled methane emissions at different times during the day. We conclude that the point source method tended to overestimate emissions, and the GreenFeed method tended to underestimate emissions. Enteric methane emissions from beef cows over the three grazing seasons averaged 0.39 and 0.25 kg d-1 cow-1 as measured by the point source and GreenFeed methods, respectively. An annualized enteric MER for a beef cow herd grazing tallgrass prairie was 0.32 kg d-1 cow-1. Quantifying enteric methane emissions from grazing beef cows remains a challenge because of the mobile, often dispersed behavior of grazing cattle and the dynamic interactions of forage quality, dry matter intake, and changing physiological state of cows during the year. Keywords: Beef cows, Enteric methane, Forage quality, Grazing, Tallgrass prairie.

Ammonia (NH 3 ) emission from beef cattle feedyard manure results in losses of nitrogen (N), which may negatively affect air, soil, and water quality. The magnitude and rate of NH 3 volatilization from feedyards partially depends on the amount of urinary urea excreted and dissociation of ammonium (NH 4 + ) into NH 3 following urea hydrolysis. Zeolite clinoptilolite is a naturally occurring, porous aluminosilicate mineral that can sorb and sequester cations within its negatively charged framework structure. Zeolite has been used to mitigate NH 3 losses and improve fertilizer value of compost, sewage sludge, and manure in livestock barns; however, few studies have evaluated its efficacy on open-lot beef cattle feedyards. Zeolite application to pen surfaces could be a practical and cost-effective means of reducing NH 3 losses. Objectives of this study were to (1) characterize NH 4 + sorption by zeolites with differing physicochemical properties and (2) evaluate zeolite effects on rates and cumulative losses of NH 3 following application of artificial urine to feedyard manure. Batch incubation studies with four commercially available zeolites revealed that NH 4 + sorption by zeolite was rapid (1 to 2 h) with large differences in sorption potential largely related to zeolite pH. Maximum sorption ranged from 28 to 97 cmol NH 4 + -N kg -1 zeolite. Effects of zeolite application rate [0.5% to 10.0% of manure dry matter (DM)] on sorption and desorption characteristics in a manure/artificial urine matrix were highly variable but tended to be proportional to zeolite application rate: as little as 0.5% zeolite increased NH 4 + -N recovery by up to 19%. In flow-through chamber studies, higher rates of zeolite did not reduce cumulative NH 3 emissions, as 1.0% zeolite reduced cumulative NH 3 emission by 42% and 5.0% zeolite reduced N losses by only 18% compared to unamended manure. Surface application of zeolite has potential for mitigating feedyard NH 3 losses, but specific zeolite properties influenced its effectiveness. Further studies are warranted to evaluate effects of repeated zeolite application, co-application of zeolite and urease inhibitors, and cost:benefit ratios of zeolite application at commercial feedyards.

Odor emissions from livestock production have become increasingly important in the past decade. Odors derived from animal feeding operations are caused by odorous VOC emitted from the mixture of feces and urine, as well as feed and silage which may be experiencing microbial fermentation. Distillers grains are a by-product of corn grain fermentation used to produce fuel ethanol, and this industry has grown rapidly throughout the U.S. in past years. Therefore, the use of wet distillers grains with solubles (WDGS) in feedlot cattle diets has also increased. The objective of this research was to determine specific VOC emissions from feces and urine or a mixture of both, from cattle fed steam flaked or dry-rolled corn (DRC)-based diets containing either 0% or 30% WDGS. Flux of dimethyl trisulfide was greater from feces of cattle fed DRC than steam-flaked corn (SFC) diets. No other differences in flux from feces were detected across dietary treatments for phenol, 4-methylphenol, indole, skatole, dimethyl disulfide, and flux of volatile fatty acids (VFA) such as acetic, propionic, isobutyric, butyric, isovaleric, and valeric acids (P > 0.15). Flux of skatole, acetic acid, and valeric acid from urine was greater for cattle fed SFC than DRC diets (P

With increased concern over the effects of livestock production on the environment, a number of new technologies have evolved to help scientists evaluate the environmental footprint of beef cattle. The objective of this review was to provide an overview of some of those techniques. These techniques include methods to measure individual feed intake, enteric methane emissions, ground-level greenhouse gas and ammonia emissions, feedlot and pasture emissions, and identify potential pathogens. The appropriate method to use for measuring emissions will vary depending upon the type of emission, the emission source, and the goals of the research. These methods should also be validated to assure they produce accurate results and achieve the goals of the research project. In addition, we must not forget to properly use existing technologies and methods such as proper feed mixing, feeding management, feed/ingredient sampling, and nutrient analysis.

Ruminant livestock provides meat and dairy products that sustain health and livelihood for much of the world’s population.Grazinglandsthatsupportruminantlivestockprovidenumerousecosystemservices,includingprovision of food, water, and genetic resources; climate and water regulation; support of soil formation; nutrient cycling; and cultural services. In the U.S. southern Great Plains, beef production on pastures, rangelands, and hay is a major economic activity. The region’s climate is characterized by extremes of heat and cold and extremes of drought and flooding. Grazing lands occupy a large portion of the region’s land, significantly affecting carbon, nitrogen, and water budgets. To understand vulnerabilities and enhance resilience of beef production, a multi-institutional Coordinated Agricultural Project (CAP), the “grazing CAP,” was established. Integrative research and extension spanning biophysical, socioeconomic, and agricultural disciplines address management effects on productivity and environmental footprints of production systems. Knowledge and tools being developed will allow farmers and rancherstoevaluaterisksandincreaseresiliencetodynamicconditions.Theknowledgeandtoolsdevelopedwillalso have relevance to grazing lands in semiarid and subhumid regions of the world.

Methane (CH) emissions from enteric fermentation by livestock account for about 2.1% of U.S. greenhouse gas emissions, with beef and dairy cattle being the most significant sources. A better understanding of CH emissions from beef cattle feedyards can help build more accurate emission inventories, improve predictive models, and meet potential regulatory requirements. Our objective was to quantify CH emissions during winter and summer at a typical beef cattle feedyard on the southern High Plains in Texas. Methane emissions were quantified over 32 d in winter and 44 d in summer using open-path lasers and inverse dispersion analysis. Methane per capita emission rate (PCER) ranged from 71 to 118 g animal d in winter and from 70 to 130 g animal d in summer. Mean CH PCER was similar in January, February, and May (average, 85.0 ± 0.95 g animal d) and increased to 93.4 g animal d during the June-July period. This increase coincided with increased dietary fiber. Methane loss ranged from 9.2 to 11.4 g CH kg dry matter intake, with lower values during winter. Gross energy intake (GEI) ranged from 135.2 to 164.5 MJ animal d, and CH energy loss ranged from 4.5 to 4.9 MJ animal d. Fraction of GEI lost as CH (Y) averaged 2.8% in winter, 3.2% in summer, and 3.0% overall. These values confirm the Y value currently recommended by the Intergovernmental Panel on Climate Change for Tier 2 estimates of enteric CH from feedlot fed cattle.

Manure from beef cattle feedyards is a valuable source of nutrients and assists with maintaining soil quality. However, humification and decomposition processes occurring during feedyard manure's on-farm life cycle influence the forms, concentrations, and availability of carbon (C) and nutrients such as nitrogen (N) and phosphorus (P). Improved understanding of manure organic matter (OM) chemistry will provide better estimates of potential fertilizer value of manure from different feedyard sources (e.g., manure accumulated in pens, stockpiled manure after pen scraping) and in settling basin and retention pond sediments. This will also assist with identifying factors related to nutrient loss and environmental degradation via volatilization of ammonia and nitrous oxide and nitrate leaching. We used Fourier-transform infrared (FTIR) and ultraviolet-visible (UV-vis) spectroscopies to characterize structural and functional properties of OM and water-extractable OM (WEOM) from different sources (surface manure, manure pack, settling basin, retention pond) on a typical commercial beef feedyard in the Texas Panhandle. Results showed that as beef manure completes its on-farm life cycle, concentrations of dissolved organic C and N decrease up to 98 and 95%, respectively. The UV-vis analysis of WEOM indicated large differences in molecular weight, lignin content, and proportion of humified OM between manures from different sources. The FTIR spectra of OM and WEOM indicate preferential decomposition of fats, lipids, and proteins over aromatic polysaccharides such as lignin. Further work is warranted to evaluate how application of feedyard manure from different sources influences soil metabolic functioning and fertility.

Nitrous oxide (NO) emissions from concentrated animal feeding operations, including cattle feedyards, have become an important research topic. However, there are limitations to current measurement techniques, uncertainty in the magnitude of feedyard NO fluxes, and a lack of effective mitigation methods. The objective of this review was to assess NO emission from cattle feedyards, including comparison of measured and modeled emission rates, discussion of measurement methods, and evaluation of mitigation options. Published annual per capita flux rates for beef cattle feedyards and open-lot dairies were highly variable and ranged from 0.002 to 4.3 kg NO animal yr. On an area basis, published emission rates ranged from 0 to 41 mg NO m h. From these studies and Intergovernmental Panel on Climate Change emission factors, calculated daily per capita NO fluxes averaged 18 ± 10 g NO animal d (range, 0.04-67 g NO animal d). This variation was due to inconsistency in measurement techniques as well as irregularity in NO production and emission attributable to management, animal diet, and environmental conditions. Based on this review, it is clear that the magnitude and dynamics of NO emissions from open-lot cattle systems are not well understood. Further research is required to quantify feedyard NO fluxes and develop cost-effective mitigation methods.

Odor and volatile organic compound (VOC) emissions are a concern at animal feeding operations (AFOs). The issue has become more prevalent as human residences move into areas once occupied only by agriculture. Odors near AFOs are generally caused by odorous VOCs emitted from manure, the mixture of feces and urine. Wet distillers grains with solubles (WDGS) are a by-product of the ethanol industry, and WDGS have become a staple in many beef cattle finishing diets. The objective of this research was to determine specific VOC emissions from frozen feces and urine of cattle fed steam-flaked corn (SFC)-based diets containing 0, 15, 30, or 45% WDGS. No differences in flux were detected across dietary treatments for phenol, indole, skatole, or 4-methylphenol (P > 0.23). Dimethyl disulfide and dimethyl trisulfide flux in feces were not different across treatments (P > 0.35) and the flux of volatile fatty acids (VFA) such as acetic, propionic, isobutyric, butyric, isovaleric, and valeric were not different across treatments (P > 0.25). There was a tendency for dimethyl disulfide flux from urine to be greater for cattle consuming an SFC-based diet with 15% WDGS than the other diets (P = 0.10). Furthermore, flux of acetic, propionic, isobutyric, butyric, and isovaleric acid from the urine were not different (P > 0.61) across dietary treatment. There were no significant differences in odor activity value (OAV) across treatments for feces, and only a tendency for dimethyl disulfide in the feces (P = 0.09). Thus, there was no obvious indication that feeding WDGS in conjunction with SFC affects flux of odor or odorous VOC from beef manure. The summed OAV was three times higher in the urine than feces, and a single odorous compound (4-methylphenol) accounted for 97.6%and 67.3% of the OAV in urine and feces, respectively. Therefore, engineering or dietary strategies to reduce odor from beef cattle manure should focus on controlling or reducing 4-methylphenol concentrations in the urine and feces.

Concentrated animal feeding operations (CAFOs) are major sources of ammonia emitted into the atmosphere. There is considerable literature on ammonia emissions from poultry and swine CAFO, but few comprehensive studies have investigated large, open lot beef cattle feedyards. Ammonia emission rates and emission factors for a 77-ha, 45 000-head commercial beef cattle feedyard on the southern High Plains were quantified using measured profiles of ammonia concentration, wind speed and air temperature, and an inverse dispersion model. Mean summer emission rate was 7420 kg NH 3 d −1 , and winter emission rate was about half that, at 3330 kg NH 3 d −1 . Annual NH 3 –N emission rate was 4430 kg NH 3 –N d −1 , which was 53% of the N fed to cattle. Daily per capita NH 3 –N losses increased by 10–64% after the daily per capita N in feed rations increased by 15–26%. Annual emission factors for the pen area of the feedyard were 19.3 kg NH 3 (head fed) −1 , or 70.2 kg NH 3 Mg −1 biomass produced. Annual emission factors for the retention pond of the feedyard were estimated to be 0.9 kg NH 3 (head fed) −1 , or 3.2 kg NH 3 Mg −1 biomass produced.

Cattle feedyards can impact local environments through emission of ammonia and dust deposited on nearby land. Impacts range from beneficial fertilization of cropland to detrimental effects on sensitive ecosystems. Shortgrass prairie downwind from an adjacent feedyard on the southern High Plains of Texas, USA changed from perennial grasses to annual weeds. It was hypothesized that N enrichment from the feedyard initiated the cascade of negative ecological change. Objectives were to determine the distribution of soil nitrogen and estimate N loading to the pasture. Soil samples were collected from 119 locations across the pasture and soil total N (TN), nitrate-N and ammonium-N (AN) determined in the top 30 cm. Soil TN concentration decreased with distance downwind from the feedyard from 1.6 ± 0.2 g kg−1 at 75 m to 1.2 ± 0.05 g kg−1 at 582 m. Nitrate-N concentration decreased within 200 m of the feedyard and changed little at greater distances. Ammonium-N concentration decreased linearly (P < 0.001) with increasing distance from the feedyard from 7.9 ± 1.7 mg kg−1 within 75 m from the feedyard to 5.8 ± 1.5 mg kg−1 at more than 550 m from the feedyard; however, distance only explained 12% of the variability in AN concentration. Maximum nitrogen loading, from 75 to 106 m from the feedyard, was 49 kg ha−1 year−1 over 34 years and decreased with distance from the feedyard. An estimate of net dry deposition of ammonia indicated that it contributed negligibly to N loading to the pasture. Nitrogen enrichment that potentially shifted vegetation from perennial grasses to annual weeds affected soil N up to 500 m from the feedyard; however, measured organic and inorganic N beyond that returned to typical and expected levels for undisturbed shortgrass prairie.

Concentrated animal feeding operations are major sources of ammonia to the atmosphere. Control methods to reduce emissions include acidifying amendments, urease inhibitors, and absorbents. For beef cattle, decreasing crude protein (CP) in diets may be the most practical and cost-effective method to reduce ammonia emissions. Our objective was to quantify the effect of reducing CP in beef cattle diet on ammonia emissions. Two groups of steers were fed diets with either 11.5 or 13.0% CP and all urine and feces were collected. Manures from the two diet treatments were applied in a replicated laboratory chamber experiment, and ammonia emission was quantified using acid gas washing. In four seasonal field trials, manures from the two diet treatments were applied to two 10-m-diameter, circular, artificial feedyard surfaces, and ammonia emission was quantified using the integrated horizontal flux method. Manure from steers fed 11.5% CP diet had less urine, less urinary N, and a lesser fraction of total N in urine, compared with the 13.0% CP diet. Decreasing crude protein in beef cattle diets from 13 to 11.5% significantly decreased ammonia emission by 44% (p < 0.01) in the closed chamber laboratory experiment, and decreased mean daily ammonia flux by 30% (p = 0.10), 52% (p = 0.08), and 29% (p < 0.01) in summer, autumn, and spring field trials, respectively. No difference was observed in winter. On an annual basis, decreasing crude protein reduced daily ammonia flux by 28%. Reducing crude protein in beef cattle diets may provide the most practical and cost-effective way to reduce ammonia emissions from feedyards.

Ammonia (NH) volatilization from manure in beef cattle feedyards results in loss of agronomically important nitrogen (N) and potentially leads to overfertilization and acidification of aquatic and terrestrial ecosystems. In addition, NH is involved in the formation of atmospheric fine particulate matter (PM), which can affect human health. Process-based models have been developed to estimate NH emissions from various livestock production systems; however, little work has been conducted to assess their accuracy for large, open-lot beef cattle feedyards. This work describes the extension of an existing process-based model, the Integrated Farm Systems Model (IFSM), to include simulation of N dynamics in this type of system. To evaluate the model, IFSM-simulated daily per capita NH emission rates were compared with emissions data collected from two commercial feedyards in the Texas High Plains from 2007 to 2009. Model predictions were in good agreement with observations and were sensitive to variations in air temperature and dietary crude protein concentration. Predicted mean daily NH emission rates for the two feedyards had 71 to 81% agreement with observations. In addition, IFSM estimates of annual feedyard emissions were within 11 to 24% of observations, whereas a constant emission factor currently in use by the USEPA underestimated feedyard emissions by as much as 79%. The results from this study indicate that IFSM can quantify average feedyard NH emissions, assist with emissions reporting, provide accurate information for legislators and policymakers, investigate methods to mitigate NH losses, and evaluate the effects of specific management practices on farm nutrient balances.

Ruminant livestock provides meat and dairy products that sustain health and livelihood for much of the world's population. Grazing lands that support ruminant livestock provide numerous ecosystem services, including provision of food, water, and genetic resources; climate and water regulation; support of soil formation; nutrient cycling; and cultural services. In the U.S. southern Great Plains, beef production on pastures, rangelands, and hay is a major economic activity. The region's climate is characterized by extremes of heat and cold and extremes of drought and flooding. Grazing lands occupy a large portion of the region's land, significantly affecting carbon, nitrogen, and water budgets. To understand vulnerabilities and enhance resilience of beef production, a multi-institutional Coordinated Agricultural Project (CAP), the "grazing CAP," was established. Integrative research and extension spanning biophysical, socioeconomic, and agricultural disciplines address management effects on productivity and environmental footprints of production systems. Knowledge and tools being developed will allow farmers and ranchers to evaluate risks and increase resilience to dynamic conditions. The knowledge and tools developed will also have relevance to grazing lands in semiarid and subhumid regions of the world.

Temperature controls many processes of NH volatilization. For example, urea hydrolysis is an enzymatically catalyzed reaction described by the Arrhenius equation. Diet crude protein (CP) controls NH emission by affecting N excretion. Our objectives were to use the Arrhenius equation to model NH emissions from beef cattle () feedyards and test predictions against observed emissions. Per capita NH emission rate (PCER), air temperature (), and CP were measured for 2 yr at two Texas Panhandle feedyards. Data were fitted to analogs of the Arrhenius equation: PCER = () and PCER = (,CP). The models were applied at a third feedyard to predict NH emissions and compare predicted to measured emissions. Predicted mean NH emissions were within -9 and 2% of observed emissions for the () and (T,CP) models, respectively. Annual emission factors calculated from models underestimated annual NH emission by 11% [() model] or overestimated emission by 8% [(,CP) model]. When from a regional weather station and three classes of CP drove the models, the () model overpredicted annual NH emission of the low CP class by 14% and underpredicted emissions of the optimum and high CP classes by 1 and 39%, respectively. The (,CP) model underpredicted NH emissions by 15, 4, and 23% for low, optimum, and high CP classes, respectively. Ammonia emission was successfully modeled using only, but including CP improved predictions. The empirical () and (,CP) models can successfully model NH emissions in the Texas Panhandle. Researchers are encouraged to test the models in other regions where high-quality NH emissions data are available.

Background The high demand for ethanol in the U.S. has generated large stocks of wet distillers grains (DG), a byproduct from the manufacture of ethanol from corn and sorghum grains. Little is known, however, about the potential influence of dietary DG on fecal microbial community structure. A better understanding of the microbial population in beef cattle feces could be an important monitoring tool to facilitate goals of improving nutrient management, increasing animal growth performance and decreasing odors and/or shedding of pathogens. Five diets consisting of a traditional diet fed to finishing beef cattle in the Southern High Plains of Texas-CON (steam-flaked corn control with 0% DG), and four concentrations of DG in the dietary dry matter; 10 C (10% corn-based DG), 5S (5% sorghum-based DG), 10S (10% sorghum DG), and 15S (15% sorghum DG) were fed to steers at the Texas Tech University Burnett Animal Center. Diets were essentially isonitrogenous with a formulated crude protein value of 13.5%. Results Fecal grab samples were obtained from 20 steers (n = 4 per diet) and the barcoded DNA pyrosequencing method was used to generate 127,530 16S operational taxonomic units (OTUs). A total of 24 phyla were observed, distributed amongst all beef cattle on all diets, revealing considerable animal to animal variation, however only six phyla (core set) were observed in all animals regardless of dietary treatment. The average abundance and range of abundance, respectively of the core phyla were as follows: Firmicutes (61%, 19 to 83%), Bacteroidetes (28%, 11 to 63%), Proteobacteria (3%, 0.34 to 17.5%), Tenericutes (0.15%, 0.0 to 0.35%), Nitrospirae (0.11%, 0.03 to 0.22%), and Fusobacteria (0.086%, 0.017 to 0.38%). Feeding DG-based diets resulted in significant shifts in the fecal microbial community structure compared with the traditional CON. Four low abundance phyla significantly responded to dietary treatments: Synergistetes (p = 0.01), WS3 (p = 0.054), Actinobacteria (p = 0.06), and Spirochaetes (p = 0.06). Conclusions This is, to our knowledge, the first study using this method to survey the fecal microbiome of beef cattle fed various concentrations of wet DG. Comparison of our results with other cattle DNA sequencing studies of beef and dairy cattle feces from a variety of geographical locations and different management practices identifies a core set of three phyla shared across all cattle. These three phyla, in order of relative abundance are; Firmicutes, Bacteroidetes, and Proteobacteria. The presence of large animal-to-animal variation in cattle microbiome was noted in our study as well as by others.

Ammonia emitted from beef cattle feedyards adds excess reactive N to the environment, contributes to degraded air quality as a precursor to secondary particulate matter, and represents a significant loss of N from beef cattle feedyards. We used open path laser spectroscopy and an inverse dispersion model to quantify daily, monthly, seasonal, and annual NH emissions during 2 yr from two commercial cattle feedyards in the Panhandle High Plains of Texas. Annual patterns of NH fluxes correlated with air temperature, with the greatest fluxes (>100 kg ha d) during the summer and the lowest fluxes (

Methane is a greenhouse gas with a global warming potential twenty-five times that of carbon dioxide. Animal production is recognized as a significant source of methane to the atmosphere. Dairies on the southern High Plains of New Mexico and Texas are typically open lot, and major sources of methane are enteric emissions from cattle and wastewater lagoons. Uncovered anaerobic lagoons are identified by the U.S. Environmental Protection Agency as a major source of methane in dairy manure management systems. Our objective was to quantify methane emissions from the wastewater lagoons of a commercial dairy located in eastern New Mexico. Research was conducted during six days in August, 2009 at a 3500-cow open lot dairy with flush alleys. Methane concentration over three interconnected lagoons (total area 1.8 ha) was measured using open path laser spectroscopy. Background methane concentration was measured using a back-flush gas chromatography system with flame ionization located upwind in the direction of prevailing winds. Wind and turbulence data were measured using a three-axis sonic anemometer. Emissions were estimated using an inverse dispersion model. Methane concentration over the lagoons ranged from 3 to 12 ppm, and averaged 5.6 ppm; background methane concentration averaged 1.83 ppm. Methane flux density ranged from 165 to 1184 µg m-2 s-1. Mean daily methane flux density was 402 kg ha-1 d-1. Per capita methane emission rate averaged 0.211 kg head-1 d-1. Uncovered anaerobic lagoons were a significant source of methane emitted from this southern High Plains dairy, and lagoons could be a significant control point for emission reduction.

Ambient NH3 concentrations were measured at a beef cattle CAFO during the spring and summer months of 2007. Concentrations were measured every five minutes, 24-hours per day at a sample intake height of 3.3 m using a chemiluminescence analyzer. On site weather data was collected concurrently. Emission rates were estimated using a backward Lagrangian Stochastic model (WindTrax 2.0.7.8). Mean 24-hr concentrations for spring were 0.498, 0.597 and 0.568 ppm for March, April and May, respectively. Corresponding fluxes for March, April and May were 57.76, 123.10 and 86.34 µg m-2 sec-1, respectively. Summer mean ambient concentrations were 0.684, 0.702 and 0.568 ppm for June, July and August, respectively. Summer fluxes were 85.27, 75.06 and 71.56 µg m-2 sec-1 for June, July and August, respectively.

Wind tunnels and flux chambers are often used to measure volatile organic compound (VOC) emissions and estimate emission factors from animal feeding operations (AFOs) without regard to air velocity or sweep air flow rates. Laboratory experiments were conducted to evaluate the effect of wind tunnel air velocity on VOC emission rates. VOC emissions were measured on standard solutions of VOCs in water, and on manure and wastewater from beef cattle and dairy AFOs at wind tunnel air velocities between 0.003 and 0.2 m/s corresponding to volumetric air exchange rates of 0.6 to 39 exchanges per minute. Activated-carbon-filtered air was passed through a small rectangular wind tunnel (30.5 cm length, 15.2 cm width, 5.1 cm height). Outlet air was sampled using stainless steel sorbent tubes (Tenax® TA) and analyzed for seven volatile fatty acids (acetic, propionic, isobutyric, butyric, isovaleric, valeric, hexanoic) and four heavier molecular weight (MW) semi-VOCs (phenol, p-cresol, indole and skatole) using gas chromatography/mass spectrometry. VOC emission rates increased linearly with increasing wind velocity. These results show that wind velocity is a major factor affecting VOC emissions from AFOs. Selection of representative air velocity or sweep air flow rate is critical when estimating VOC emission factors using wind tunnels and flux chambers.

Ammonia emissions from cattle feedyards may comprise 40% or more of nitrogen intakes. Decreasing ammonia emissions would improve the fertilizer value of feedyard manure and decrease potential adverse effects on the environment. Two trials were conducted to evaluate the effects of fat and zeolite on potential ammonia emissions from a feedlot surface. In the first trial corn oil, alum, a urease inhibitor, or potassium zeolite were added to simulated feedlot surfaces in lab-scale chambers and ammonia losses were captured using an acid solution. In trial two, five beef steers were fed one of five finishing diets (0% added fat, 3% added fat, 6% added fat, 3% fat+1% zeolite, or 3% fat+2% zeolite) in a 5 x 5 Latin square. During the last 5 days of each period feces and urine output were collected in stalls to determine nutrient digestion and retention. Feces and urine from each steer were used in the lab-scale flow-through chambers to estimate potential ammonia losses. In trial 1, zeolite and fat additions decreased ammonia losses by 51 to 86%; however the effects were not additive. In trial 2, apparent protein digestion, nitrogen retention, and nitrogen excretion were not affected by dietary fat or zeolite. In vitro ammonia losses were not significantly affected by dietary zeolite; however in vitro ammonia losses were greater (P < 0.05) when steers were fed diets containing no added fat. These results suggest that fat and zeolites can potentially decrease ammonia emissions from beef cattle feedyards.

Concentrated animal feeding operations are major sources of ammonia emitted to the atmosphere. There is a considerable literature on ammonia emissions from poultry and swine, but few studies have investigated large, open lot beef cattle feedyards. We used the micrometeorological flux-gradient method to estimate ammonia emissions during six field campaigns in three seasons. Profiles of ammonia, wind speed and air temperature were measured on towers located within feedyard pens. Atmospheric ammonia concentration was measured using either acid gas washing or chemiluminescence. Mean daily ammonia flux in summer averaged 72 µg m-2 s-1, and in winter, 39 µg m-2 s-1. Springtime fluxes were highly variable and averaged 79 µg m-2 s-1; high springtime fluxes were attributed to greater ammonium concentration in manure and high wind speeds. Ammonia-N emisson rate averaged 3930 and 2150 kg d-1 in summer and winter, respectively, which was 45% and 27% of fed N. Assuming that the mean of summer and winter emission rates represented a mean annual emission, ammonia-N loss was 36% of fed N, and an annual emission factor for feedyard pens based on total yearly per head production was 11.0 kg NH3-N head-1 yr-1. Ammonia emissions increased after N in cattle rations was increased from 13.5% to 14.5%. Ammonia emissions estimated using the flux-gradient method were 22 to 36% less than those derived from an inverse dispersion model. Uncertainty in the Schmidt number and possible violation of the assumption of homogeneous flow could have contributed to the lower flux estimates of the flux-gradient method. Optimizing fed N through practices such as phase feeding could help minimize ammonia emissions. Longer term, more continuous monitoring of ammonia emissions is needed to better define annual variability, emission rates and factors, and facilitate development of process models.

Dynamic, flow-through flux chambers are sometimes used to estimate ammonia emissions from livestock operations, however, ammonia emissions from the surfaces are affected by many factors which can be affected by the chamber. Ammonia emissions estimated using environmental flow-through chambers may be affected by air exchange rate; however, chamber fluxes have not been directly compared to the flux from the same source when unaffected by a chamber. We compared measured ammonia losses from an unaffected source to the same source when the air exchange rate ranged from 0 to 4 turnovers per minute. To simulate a feedlot retention pond, buffered ammonium sulfate solutions with pH values of 7.6, 8.6, or 9.6 were used as the ammonia source. To simulate a feedlot surface, similar solutions were added to a cellulose media. With both surfaces, ammonia losses increased with increased air flow. Losses at 0.5 turnovers/min were 25% or less that of losses from the unaffected sources. At low flow rates source strength differences were sometimes not accurately determined. There is a large spatial variability in ammonia flux from pen surfaces (CV = 23 to 192%). Because of this variability, the number of ammonia flux estimates required to be 95% confident that the estimated mean is within 20% of the true mean (determined as CV2/100) ranges from 5 to 369. The results of these studies suggest that dynamic flux chambers will not give accurate estimates of ammonia losses from either liquid or solid surfaces when flow rates are less than 10 to 15 air exchanges per minute and that large numbers of samples and(or) proper experimental design are required when using chambers for treatment comparisons.

The biological and chemical characteristics of feedyard pen surfaces have the potential to affect environmental conditions with respect to air and water quality. Little is known about feedyard pen surface chemistry and that of the underlying microbial community structure. The feedlot surface profile has been described as four layers: the unconsolidated (or loose surface), dry-pack, wet-pack, and soil layer. It was determined that NO3-N concentration was greater in the soil layer than in the manure layers whereas NH4-N concentration was greatest in the wet-pack layer. In this study, we characterized the microbial communities associated with these four feedlot layers using the DGGE-PCR method employing a suite of primers that target 16S and 18S rDNA. The distribution of microorganisms intimately involved in the cycling of N such as the ammonia-oxidizing bacteria (AOB) found within the Betaproteobacteria and the nitrite-oxidizing bacteria (NOB) found in the Alphaproteobacteria division was determined. The influence of the feedlot layers on microbial community structure was observed in the spatial grouping of DNA fingerprint patterns and as assessed by two indices of diversity. Different lineages of AOB were found to be associated with these feedlot layers which imply a microbial ecosystem that is uniquely influenced by the physical and chemical properties of these feedlot layers. Both AOB and NOB communities are present in all feedyard pen surface layers for nitrification of ammonia to occur. The wet-pack layer showed a marked reduction in both fungal diversity and evenness. A feedlot pen surface may be viewed as a distinct microbiological island.

We conducted field experiments to evaluate how factors such as sweep air flowrate, time since urine deposition, and flux chamber footprint area affect ammonia fluxes from open-lot feedyard and dairy surfaces as measured using three different flux chamber designs. The chambers included a 26.5-cm diameter chamber (North Carolina State University design), a 49-cm diameter chamber (EPA-type design), and a 1.2 m x 2.4 m rectangular chamber (West Texas A&M University design). Clean sweep air collected upwind of the feedyard (

A laboratory study was conducted to evaluate how rate and timing of urease inhibitor application affects ammonia emissions from simulated beef cattle feedyard surfaces. The urease inhibitor N-(n-butyl)thiophosphoric triamide (NBPT) was applied at rates of 0, 1 and 2 kg/ha, at 8, 16, and 32 day frequencies, and with or without simulated rainfall. Synthetic urine was added every 2 days to the manure surface. Gaseous NH3 was trapped in a sulfuric acid solution using a vacuum system and analyzed for nitrogen using automated procedures. NBPT applied every 8 days was most effective, with the 1 and 2 kg/ha NBPT treatments resulted in 49 and 66% reduction in NH3 emission rates, respectively. The 8-day, 1 kg/ha NBPT treatment had the most promising cost/benefit ratio of 0.48. Simulated rainfall reduced the NH3 emission rates slightly as compared to the non-rainfall treatments, though the differences were not statistically different.

A laboratory study was performed to compare ammonia emissions from simulated feedlot surfaces. Beef cattle manure was collected from open lot pens at the USDA-ARS feedlot in Bushland, TX. Treatments within the pens consisted of two dietary crude protein concentrations (11.5 and 13%) and two protein sources (urea and cottonseed meal). Manure collected from the pens was placed into Tupperware® chambers in the laboratory. Chambers were sealed and ammonia was trapped in an acid solution for 15 days using a vacuum system. Results suggest that as the protein concentration in the diet increases, potential daily ammonia emissions increase. The source of crude protein had little effect on ammonia emissions.

A dynamic flow-through chamber system and continuous analyzers were used for on-site measurements of ammonia-nitrogen (NH3-N) and hydrogen sulfide-sulfur (H2S-S) fluxes from commercial feedlot surfaces in northwestern Texas during two week period in the summer of 2002. Manure pack moisture content, pH, and TKN were measured daily to characterize its relation with NH3-N fluxes. The preliminary average NH3-N and H2S-S flux from the feedlot surface were 1,669 ± 1,212 NH3-N µg/m2/min and 1.884 ± 1.497 H2S-S µg S/m2/min. Manure pack temperature and TKN was found to have a weak correlation with NH3-N flux.

Biogas production at beef cattle feedlots is hard to justify because of the large amounts of dilution water required and the high cost to design and operate conventional water-based digestion systems. Laboratory and field experiments were conducted to determine the feasibility of producing biogas using "dry" aged beef cattle manure scraped from open-lot feedyards. Biogas production rates were measured at 21°C in the laboratory at four total solids contents using a water displacement technique. Biogas yields were 0.180, 0.210, 0.190 and 0.005 L per gram volatile solids (VS) at solids contents of 20, 30, 40 and 50 percent, respectively. Biogas was produced steadily for 300 days before declining and eventually ceasing after 450 days. The biogas contained 52 to 60 The authors are solely responsible for the content of this technical presentation. The technical presentation does not necessarily reflect the official position of the American Society of Agricultural Engineers (ASAE), and its printing and distribution does not constitute an endorsement of views which may be expressed. Technical presentations are not subject to the formal peer review process by ASAE editorial committees; therefore, they are not to be presented as refereed publications. Citation of this work should state that it is from an ASAE meeting paper. EXAMPLE: Author's Last Name, Initials. 2002. Title of Presentation. ASAE Meeting

Volatile fatty acids (VFAs) are a major component of odorous gases associated with agricultural sources. Because of typically low VFA air concentrations, conventional air sampling methods including sorbent tubes and vacuum canisters are often not sensitive enough to detect them. Solid phase microextraction (SPME) was used in this research because it is very sensitive, reusable, fast, and combines sampling and sample preparation, allowing for rapid detection of low concentrations of organics in air. This research focused on 7 VFAs: acetic, propionic, isobutyric, butyric, isovaleric, valeric, and hexanoic acids. Field experiments were conducted to test this method for air sampling of beef cattle feedyard, horse manure compost, and a swine operation in Texas. Rapid SPME samples were collected by exposing DVB/ Carboxen/PDMS 50/30 µm SPME fibers to air for 1 to 5 min. Sample preservation was accomplished by plugging of fiber assemblies with simple PTFE caps for transport to the laboratory for analysis on gas chromatograph- mass spectrometer (GC-MS). SPME DVB/Carboxen/PDMS 50/30 µm coating was very effective in detecting target VFAs and other gaseous components of agricultural odors. This coating was also very efficient in retaining major fraction of target VFAs.

The antimicrobial susceptibilities of 421 Pasteurella haemolytica and 158 P. multocida isolates recovered from cattle with respiratory disease were determined with a microdilution minimal inhibitory concentration test system. Isolates were analyzed for patterns of resistance to ampicillin, ceftiofur, erythromycin, gentamicin, penicillin, spectinomycin, sulfachlorpyridazine, sulfadimethoxine, tetracycline, and tylosin. All isolates tested were found susceptible to ceftiofur and sulfachlorpyridazine. Pasteurella haemolytica isolates were resistant to ampicillin, penicillin, sulfadimethoxine, tetracycline, and tylosin. Pasteurella multocida isolates were resistant to sulfadimethoxine, tetracycline, and tylosin.

Ammonia and hydrogen sulphide flux and dry deposition velocity were estimated using micrometeorological vertical gradient flux method at a commercial cattle feedyard of approximately 50,000 head of beef cattle and average 14.4 m²/head (150 ft²/head) stocking density. Ammonia-N and H2S-S loss had general diurnal patterns with the highest fluxes in daytime and lowest fluxes in nighttime that correlated to temperature changes and active evaporation process during daytime. The highest average deposition velocities also occurred during daytime with unstable atmospheric conditions and the lowest during nighttime with very stable conditions. There are exponential relationship between NH3-N flux and ambient temperature with R² = 0.57 for NH3 (NH3-N flux = – 1.46 + 7.96e0.077*Temperature) and R² = 0.22 for H2S-S (H2S-S flux = – 0.75 + 0.8e-0.013*Temperature).

Preconditioning is a theoretically sound concept; however, it has not gained wide acceptance by cow-calf producers or feeders owing to logistics and expense. Many of the claims of preconditioning are not substantiated by controlled research data. Many of the positive claims made for preconditioning may be a result of the calves moving more rapidly through the marketing channels. Although preconditioning is profitable to some producers, on the average, preconditioning is difficult to justify economically. Modifications of the preconditioning concept have the potential to make it more feasible to the majority of cow-calf producers. Any producer or feeder considering a preconditioning program or feeding preconditioned calves should first calculate an economic projection.