Manure Pack Research Articles

Comparative microbiome analysis of beef cattle, the feedyard environment, and airborne particulate matter as a function of probiotic and antibiotic use, and change in pen environment.

Intensive beef cattle production systems are frequently implicated as a source of bacteria that can be transferred to nearby humans and animals via effluent water, manure used as fertilizer, or airborne particulate matter. It is crucial to understand microbial population dynamics due to manure pack desiccation, antibiotic usage, and antibiotic alternatives within beef cattle and their associated feedyard environment. Understanding how bacterial communities change in the presence of antibiotics can also improve management practices for reducing the spread of foodborne bacteria. In this study, we aimed to compare the microbiomes within cattle feces, the feedyard environment and artificially produced airborne particulate matter as a function of pen change and treatment with tylosin or probiotics. We utilized 16S rRNA sequencing to compare bacterial communities among sample types, study days, and treatment groups. Bacterial community diversity varied as a function of sampling day and pen change (old or new) within fecal and manure pack samples. Manure pack samples from old pens and new pens contained diverse communities of bacteria on days 0 and 84; however, by day 119 of the study these taxonomic differences were less evident. Particulate matter samples exhibited significant differences in community diversity and predominant bacterial taxa compared to the manure pack they originated from. Treatment with tylosin did not meaningfully impact bacterial communities among fecal, environmental, or particulate matter samples; however, minor differences in bacterial community structure were observed in feces from cattle treated with probiotics. This study was the first to characterize and compare microbial communities within feces, manure pack, and airborne particulate matter from the same location and as a function of tylosin and probiotic treatment, and pen change. Although fecal and environmental samples are commonly used in research studies and other monitoring programs to infer public health risk of bacteria and antimicrobial resistance determinants from feedyard environments, our study suggests that these samples may not be appropriate to infer public health risk associated with airborne particulate matter.

Temporal and Spatial Variability of Methane Emissions from Texas Open-Lot Beef Cattle Feedyard Pens

HighlightsOpen-lot beef cattle feedyards are a source of greenhouse gas emissions.Pen surface methane emissions were quantified during the cool and warm seasons.Methane was generated in the lower anaerobic layers of the manure pack.Methane emissions decreased after rainfall due to methane oxidation or blocking of pore space.Pen surface methane emissions accounted for <1% of overall feedyard GHG as CO2eq.Abstract. Texas is one of the top beef-producing states, where annually more than five million beef cattle are finished in large feedyards on earthen-surfaced pens. Manure deposited on open-lot pen surfaces can contribute to greenhouse gas (GHG) emissions such as methane (CH4). Two week-long sampling campaigns were conducted in April (cool season) and August (warm season) to quantify CH4 emissions from the feedyard pen surface. Emissions were monitored before and after 12.7 mm simulated rainfall events. Temporal and spatial variabilities in emissions were quantified using automated recirculating flux chambers, a multiplexer system, and a real-time CH4 analyzer. During the cool season, mean CH4 flux was 1.09 (SD ±2.39) and 0.12 (±0.25) g animal-1 d-1 before and after rainfall, respectively. During the warm season, mean CH4 flux was 0.65 (±1.01) and 0.26 (±0.44) g animal-1 d-1 before and after rainfall, respectively. This suggested that CH4 was produced in the lower, anaerobic layer of the manure pack and CH4 emissions were inhibited following rainfall, most likely due to microbial oxidation of CH4 in the upper layers through methanotrophy or from slowing of diffusion by blocking the manure pore space. The overall mean pen surface CH4 flux was 0.53 g animal-1 d-1. This flux accounted for a small percentage (<1%) of the overall estimated feedyard GHG emissions expressed as CO2eq. Thus, efforts to mitigate GHG from open-lot beef cattle feedyards in the Texas Panhandle should focus on sources with higher percentages of overall GHG, such as enteric methane, pen surface nitrous oxide, and nitrous oxide from fertilized cropland. Keywords: Beef cattle, Flux chamber, Greenhouse gas, Manure, Methane, Rainfall.

Nitrous Oxide and Methane Emissions from Beef Cattle Feedyard Pens Following Large Rainfall Events

HighlightsNitrous oxide and methane emissions were measured from a commercial beef feedyard following large rainfall events.Nitrous oxide emissions dropped below detection levels for ten days following a 77 mm rainfall event.Daily N2O and CH4 emissions followed a diel pattern, peaking at manure temperatures of 36°C to 38°C.Results will be used to refine empirical models for predicting GHG emissions from open-lot feedyards.Abstract. More than six million beef cattle are fed annually in feedyards on the semiarid Southern Great Plains (SGP). Manure deposited on the open-lot pen surfaces contributes to greenhouse gas (GHG) emissions. Nitrous oxide (N2O) and methane (CH4) are GHGs linked to climate change, and both have global warming potentials greater than carbon dioxide (CO2). Two sampling campaigns were conducted in 2019 to quantify N2O and CH4 emissions from open-lot pen surfaces. The occurrence of large, unforecast rainfall events during both campaigns provided an opportunity to compare GHG emissions from the dry manure before rainfall and from the wetted pen surface for one to two weeks following precipitation. Temporal variability was quantified by continuous sampling using six to eight automated flux chambers, a multiplexer system, and real-time analyzers. Spatial variability was quantified using a recirculating portable chamber on a 5 × 8 grid. Nitrous oxide emissions dropped below detection levels for ten days after the precipitation event. Nitrous oxide emissions were related to nitrification or other aerobic processes. Methane emissions dropped below detection levels for five days after the precipitation event and then increased to pre-rainfall levels by day 8. When present, N2O and CH4 emissions followed a diel pattern, with the highest emissions occurring during the afternoon when manure pack temperatures at the 25 mm depth were 36°C to 38°C and ambient temperatures were 31°C to 32°C. Average CH4 emissions from the feedyard pen surface were 96-fold lower than estimated enteric CH4 emissions. The results of this field research will be used to refine empirical models for predicting annual N2O and CH4 emissions from open-lot beef cattle feedyards on the semiarid SGP. Keywords: Beef cattle, Flux chamber, Greenhouse gas, Manure, Nitrous oxide, Rainfall.

Nitrous Oxide from Beef Cattle Manure: Effects of Temperature, Water Addition and Manure Properties on Denitrification and Nitrification

Beef feedyards produce nitrous oxide (N2O), a potent greenhouse gas. Limited research has evaluated the processes that produce feedyard N2O, and how rainfall and temperature impact N2O losses. Manure in feedyard pens develops into a complex ecosystem of microbes, extracellular enzymes, feces, and urine, with varying H2O content. This study aimed to improve understanding of feedyard N cycling under differing environmental conditions by incubation of manure in simulated feedyard pens using large chambers under laboratory conditions. We hypothesized that nitrification was the primary source of feedyard N2O, with interactions among temperature, H2O content, and manure properties. Emissions of N2O were monitored with a real–time N2O analyzer. Manure samples were taken at intervals for analyses of physicochemical properties, denitrification enzyme activity (DEA), and nitrification activity (NA). Due to equipment limitations, there was only one chamber per temperature tested. Correlation was poor among N2O emissions and rates of DEA and NA. However, significant relationships were found among key manure characteristics, such as ammonia/ammonium and nitrate/nitrite concentrations, manure dry matter, redox status, and temperature. These data suggest that most N2O was derived from denitrification in the top 5 cm of the manure pack. Further study is warranted to identify the processes involved in flushes of N2O emitted immediately after rainfall, possibly due to abiotic chemical reactions that release N2O sequestered in manure pores.

Macrolide-susceptible probiotic Enterococcus faecium ST296 exhibits faecal-environmental-oral microbial community cycling among beef cattle in feedlots.

Enterococci are included in the United States National Antimicrobial Resistance Monitoring System to track antibiotic resistance among commensal Gram-positive enteric bacteria, largely due to their high abundance in food animals and in retail meat. In the U.S. cattle industry, macrolides are used to prevent and control liver abscesses, which cause significant economic losses. Previous studies have suggested that feeding tylosin and the intensity of the pen environment, both expand and sustain respectively the prevalence of multidrug resistance among enterococci in feedlot cattle. This has led to research into alternative feed supplements and improved stewardship practices. In a randomized controlled trial, we measured the impact of a probiotic and an altered pen environment on antimicrobial resistance among faecal Enterococcus spp. in cattle fed tylosin. Supplementing cattle with an Enterococcus faecium and Saccharomyces cerevisiae-based probiotic yielded the isolation of E. faecium of the probiotic sequence type (ST296) from faecal and environmental samples in treatment groups, as well as from cattle and the manure pack in nearby pens. Of importance, the probiotic strain also was found in a desiccated and milled manure pack sample taken 120days after the initial trial ended. Phylogenetic and SNP analyses revealed clonal survival and spread compatible with faecal-environmental-oral recycling of the probiotic strain within and among cattle and pens. The increase in prevalence of the ST296 strain occurred concomitant with a decrease in ST240, the dominant sequence type associated with ermB and tet(M) resistance genes in this trial. SIGNIFICANCE AND IMPACT OF THE STUDY: We demonstrate that a macrolide-susceptible probiotic Enterococcus faecium ST296 strain fed to beef cattle becomes fully embedded in the microbial community cycling of bacteria via faecal-environmental-oral transmission within and among feedlot pens. An initial investment in feeding the probiotic is thereby leveraged into expanding numbers of susceptible bacteria in cattle and their environment, even among those cattle fed tylosin.

Greenhouse gas emissions from dairy manure management in a Mediterranean environment

Livestock agriculture is a major source of anthropogenic greenhouse gas (GHG) emissions, with a substantial proportion of emissions derived from manure management. Accurate estimates of emissions related to management practices and climate are needed for identifying the best approaches to minimize, and potentially mitigate, GHG emissions. Current emissions models such as those of the IPCC, however, are based on emissions factors that have not been broadly tested against field-scale measurements, due to a lack of data. We used a diverse set of measurements over 22months across a range of substrate conditions on a working dairy to determine patterns and controls on soil-based GHG fluxes. Although dairy soils and substrates differed by management unit, GHG fluxes were poorly predicted by these or climate variables. The manure pile had the greatest GHG emissions, and though temperature increased and O2 concentration decreased following mixing, we detected almost no change in GHG fluxes due to mixing. Corral fluxes were characterized by hotspots and hot moments driven by patterns in deposition. Annual scraping kept the soil and accumulated manure pack thin, producing drier conditions, particularly in the warm dry season. Summed over area, corral fluxes had the greatest non-CO2 global warming potential. The field had net CH4 consumption, but CH4 uptake was insufficient to offset N2 O emissions on an area basis. All sites emitted N2 O with a similar or greater climate impact than CH4 . Our results highlight the importance of N2 O emissions, a less commonly measured GHG, from manure management and present potential opportunities for GHG emissions reductions.

Nitrous Oxide Emissions from Southern High Plains Beef Cattle Feedyards: Measurement and Modeling

Abstract. The Texas Panhandle produces approximately 42% of finished beef in the U.S., and cattle production is estimated to contribute 8 Tg carbon dioxide equivalents (CO2e) from nitrous oxide (N2O). Production of N2O in manure is largely a result of biochemical processes that are not static: N2O emission rates are dependent on numerous environmental and chemical factors. Process-based models that estimate N2O emissions from manure in open-lot cattle production systems typically rely on information derived from studies of soil biochemistry. Limited study has been conducted on manure-derived N2O in open-lot beef feedyards. The objectives of this study were to determine variables related to N2O losses from Texas Panhandle feedyards and develop empirical models to predict N2O emissions. Nitrous oxide flux data were collected from a series of 15 non-flow-through, non-steady-state (NFT-NSS) chamber studies (ten chambers per study) conducted from 2012 to 2014 on two commercial beef cattle feedyards. Manure samples (loose surface manure and the underlying manure pack) were analyzed for basic physicochemical properties, soluble carbon (C) and nitrogen (N), and ultraviolet-visible (UV-vis) spectral characteristics related to degree of organic matter (OM) stability and humification. Measured N2O emissions ranged from below detection to 101 mg m-2 h-1 (average 4.8 ±12 mg m-2 h-1) and were positively related to manure H2O content, temperature, and nitrate (NO3-) concentration (p < 0.01). Emissions were negatively related to manure OM, ammonia/ammonium (NH3/NH4+), dissolved C and dissolved N concentrations, and UV-vis parameters related to OM stability (p < 0.05). Based on these data, empirical models were developed and evaluated to predict manure-derived N2O emissions. Model predictions were not significantly different from observed N2O emissions (p < 0.05). The unbounded index of agreement (IA) indicated that model predictions were within 52% to 61% agreement with observations. Inclusion of OM characteristics improved model predictions of high (>30 mg m-2 h-1) N2O emissions but tended to overestimate low emission rates (<20 mg N2O m-2 h-1). This provides evidence for the importance of C stability in limiting manure N2O production. These models may improve parameterization of existing process-based models and are novel methods for predicting feedyard N2O emissions. Keywords: Beef cattle, Feedlot, Feedyard, Greenhouse gas, Manure, Modeling, Nitrous oxide, Organic matter, Urine, UV-vis spectroscopy.

Distillers By-Product Cattle Diets Enhance Reduced Sulfur Gas Fluxes from Feedlot Soils and Manures.

Total reduced sulfur (TRS) emissions from animal feeding operations are a concern with increased feeding of high-sulfur distillers by-products. Three feeding trials were conducted to evaluate feeding wet distillers grain plus solubles (WDGS) on TRS fluxes. Fresh manure was collected three times during Feeding Trial 1 from cattle fed 0, 20, 40, and 60% WDGS. Fluxes of TRS from 40 and 60% WDGS manures were 3- to 13-fold greater than the 0 and 20% WDGS manures during the first two periods. In the final period, TRS flux from 60% WDGS was 5- to 22-fold greater than other WDGS manures. During Feeding Trial 2, 0 and 40% WDGS diets on four dates were compared in feedlot-scale pens. On two dates, fluxes from mixed manure and soil near the feed bunk were 3.5-fold greater from 40% WDGS pens. After removing animals, soil TRS flux decreased 82% over 19 d but remained 50% greater in 40% WDGS pens, principally from the wetter pen edges (1.9-fold greater than the drier central mound). During two cycles of cattle production in Feeding Trial 3, TRS soil fluxes were 0.3- to 4-fold greater over six dates for pens feeding WDGS compared with dry-rolled corn diet and principally from wetter pen edges. Soil TRS flux correlated with %WDGS, total N, total P, manure pack temperature, and surface temperature. Consistent results among these three trials indicate that TRS fluxes increase by two- to fivefold when cattle were fed greater levels of WDGS, but specific manure management practices may help control TRS fluxes.

Process-Based Modeling of Ammonia and Nitrous Oxide Emissions from Open-Lot Beef and Dairy Facilities

Abstract. Airborne emissions, such as ammonia (NH3) and nitrous oxide (N2O), vary considerably among open-lot beef and dairy operations as influenced by climate and manure pack conditions. Because of the challenges with direct measurement, process-based modeling is a recommended approach for estimating airborne emissions from animal feeding operations, such as open lots. The Integrated Farm System Model (IFSM), a whole-farm simulation model for crop, dairy, and beef operations, was previously used (ver. 4.0) to simulate NH3 emissions from open lots and performed well in representing emissions for two beef cattle feedyards in Texas. However, the previous model was found to perform poorly in predicting NH3 emissions measured at two open-lot dairies in Idaho, so further work was done to better represent the effects of climate on lot and manure pack conditions and to integrate better models for nitrification and denitrification processes. The revised model (ver. 4.1) appropriately predicted NH3 emissions for the two Texas beef cattle feedyards, with model predictions having 59% and 81% agreement with measured daily emissions at each lot. Compared to the previous version, the revised model performed better in simulating NH3 emissions for the Idaho open-lot dairies, with 56% to 74% agreement between predicted and measured daily NH3 emissions. For an Idaho dairy with a freestall barn and open lot, the revised model simulated NH3 emissions with 92% agreement between predicted and measured values. Based on measurements obtained at two of the Idaho dairies, IFSM also predicted daily N2O emissions with good agreement (64% to 80%) to measured values. Hence, IFSM can be used to estimate open-lot emissions of NH3 and N2O along with other aspects of performance, environmental impact, and economics of cattle feeding operations in different climatic regions. The model provides a tool for evaluating management strategies to mitigate emissions and improve the sustainability of beef and dairy production systems.

Field measurement of beef pen manure methane and nitrous oxide reveals a surprise for inventory calculations.

Few data exist on direct greenhouse gas emissions from pen manure at beef feedlots. However, emission inventories attempt to account for these emissions. This study used a large chamber to isolate NO and CH emissions from pen manure at two Australian commercial beef feedlots (stocking densities, 13-27 m head) and related these emissions to a range of potential emission control factors, including masses and concentrations of volatile solids, NO, total N, NH, and organic C (OC), and additional factors such as total manure mass, cattle numbers, manure pack depth and density, temperature, and moisture content. Mean measured pen NO emissions were 0.428 kg ha d (95% confidence interval [CI], 0.252-0.691) and 0.00405 kg ha d (95% CI, 0.00114-0.0110) for the northern and southern feedlots, respectively. Mean measured CH emission was 0.236 kg ha d (95% CI, 0.163-0.332) for the northern feedlot and 3.93 kg ha d (95% CI, 2.58-5.81) for the southern feedlot. Nitrous oxide emission increased with density, pH, temperature, and manure mass, whereas negative relationships were evident with moisture and OC. Strong relationships were not evident between NO emission and masses or concentrations of NO or total N in the manure. This is significant because many standard inventory calculation protocols predict NO emissions using the mass of N excreted by the animal.

Particulate Matter Concentrations for Mono-Slope Beef Cattle Facilities in the Northern Great Plains

Abstract. Mono-slope beef cattle facilities are an increasingly common housing system in the Northern Great Plains region of the U.S. Producers may maintain a deep-bedded manure pack (pack system), remove all bedding and manure from the pens weekly (scrape system), or use a combination of management styles. The objectives of this research were to determine baseline particulate matter (PM) concentrations around the immediate barn perimeter and to identify relationships between management practices and PM concentrations. PM was measured over two five-day periods at one pack system barn to determine differences in PM concentration between routine operation and a bedding event. The overall mean concentration of total suspended particulates (TSP) in the pack barn was 58.6 ±3.9 I¼g m -3 during routine operation and 702.2 ±3.9 I¼g m -3 during bedding events. The mean concentrations of PM less than 10 I¼m in diameter (PM 10 ) and PM less than 2.5 I¼m in diameter (PM 2.5 ) were 4.9 ±3.0 I¼g m -3 and 17.5 ±12.1 I¼g m -3 , respectively, during routine operation and 29.7 ±4.6 I¼g m -3 and 141.7 ±18.9 I¼g m -3 , respectively, during a bedding event. The PM concentrations returned to baseline within 18 h following a bedding event. In two scrape system barns, 24 h collections of PM 10 and PM 2.5 occurred at least twice during each quarter during a 14-month period. Daily mean concentrations of PM 2.5 and PM 10 in the scrape barns ranged from 10 to 14 I¼g m -3 and from 25 to 28 I¼g m -3 , respectively, indicating relatively low PM concentrations from mono-slope beef facilities. Ambient air temperature affected PM concentration, while relative humidity, number of cattle, and wind speed were less influential on overall dust in the facilities.

Characterization of organic matter in beef feedyard manure by ultraviolet-visible and fourier transform infrared spectroscopies.

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.

Nutrient losses in runoff from feedlot surfaces as affected by unconsolidated surface materials

Beef cattle feedlots contain unconsolidated surface materials (loose manure pack) that accumulate during a feeding cycle. The effects of varying amounts of unconsolidated surface materials on runoff nutrient losses are not well understood. The objectives of this study were to (1) compare runoff nutrient losses from feedlot surfaces containing varying amounts of unconsolidated surface materials, (2) determine if differences in runoff nutrient losses exist among rainfall simulation runs, (3) relate runoff nutrient losses to selected feedlot soil characteristics, and (4) identify the effects of varying runoff rate on nutrient loss rates from feedlot surfaces. This study was conducted on 0.75 m wide by 2 m long (2.47 ft wide by 6.58 ft long) plots containing 0, 6.7, 13.5, or 26.9 kg m⁻² (0, 1.37, 2.77, or 5.51 lb ft⁻²) of unconsolidated surface materials. Simulated rainfall was applied during three 30-minute events that were separated by 24-hour intervals. Inflow was added at the top of all plots during selected tests to examine the effects of varying flow rate on nutrient loss rates. No significant differences in the measured water quality parameters were found among the surfaces containing varying amounts of unconsolidated surface materials. Measurements of dissolved phosphorus, particulate phosphorus, total phosphorus, ammonium nitrogen, chloride, total dissolved solids, electrical conductivity, and erosion consistently decreased during the three rainfall simulation runs. Runoff losses of ammonium nitrogen (NH₄-N), total nitrogen, and nitrate nitrogen were all correlated to easily obtained soil EC measurements. All measured water quality parameters were significantly influenced by runoff rate. Thus, runoff rate, and not the amount of unconsolidated surface materials on the feedlot surface, significantly influenced nutrient losses in runoff.

Nutrient and Bacterial Transport in Runoff from Soil and Pond Ash Amended Feedlot Surfaces

The addition of pond ash (fly ash that has been placed in evaporative ponds and subsequently dewatered) to feedlot surfaces provides a healthier environment for livestock and economic advantages for the feedlot operator. However, the water quality effects of pond ash amended surfaces are not well understood. The objectives of this field investigation were to: (1) compare feedlot soil properties, and nutrient and bacterial transport in runoff, from pond ash amended surfaces and soil surfaces; (2) compare the effects of unconsolidated surface materials (USM) (loose manure pack) and consolidated subsurface materials (CSM) (compacted manure and underlying layers) on nutrient and bacterial transport in runoff; and (3) determine if the measured water quality parameters are correlated to soil properties. Simulated rainfall events were applied to 0.75 m wide 2 m long plots with different surface materials and surface conditions. Measurements of calcium, magnesium, sulfur, and pH were found to be significantly greater on the pond ash amended surfaces. In comparison, the soil surfaces contained significantly greater amounts of Bray 1-P. The runoff load of NH4-N was significantly greater on the pond ash amended surfaces, while the total phosphorus (TP) load was significantly greater on the soil surfaces. The NO3-N and total nitrogen (TN) loads in runoff were significantly greater on the feedlot surfaces containing CSM. Concentrations of E. coli in runoff were similar on the pond ash amended surfaces and soil surfaces. The dissolved phosphorus (DP), particulate phosphorus (PP), and TP load of runoff were all significantly correlated to Bray 1-P measurements.

Spatial Variations in Nutrient and Microbial Transport from Feedlot Surfaces

Nutrient and microbial transport by runoff may vary at different locations within a beef cattle feedlot. If the areas making the largest contributions to nutrient and microbial transport can be identified, it may be possible to institute site-specific management practices to reduce runoff nutrient and microbial transport. The objectives of this study were to: (1) measure selected feedlot soil properties and nutrient and microbial transport in runoff from various feedlot locations, (2) compare the effects of unconsolidated surface materials (USM) (loose manure pack) and consolidated subsurface materials (CSM) (compacted manure and underlying layers) on nutrient and microbial transport, and (3) determine if nutrient and microbial transport in runoff are correlated to selected feedlot soil characteristics. Simulated rainfall events were applied to 0.75 m wide by 2 m long plots. No significant differences (P < 0.05) in feedlot soil characteristics or nutrient transport in runoff were found between USM and CSM. However, concentrations of E. coli were significantly greater in the USM than the CSM. Pen location was found to significantly influence feedlot soil measurements of Bray-1 P, calcium, chloride, copper, electrical conductivity (EC), loss on ignition, organic N, phosphorus, potassium, sodium, sulfur, total N (TN), water-soluble P, and zinc. Runoff measurements of dissolved phosphorus (DP), EC, and NH4-N were significantly influenced by pen location and were correlated to selected feedlot soil characteristics. Thus, it may be possible to estimate DP, EC, and NH4-N in runoff from selected feedlot soil parameters.

Effect of low and high forage diet on enteric and manure pack greenhouse gas emissions from a feedlot

The objectives of this study were to assess enteric methane (CH4) production by beef steers fed one of two isocaloric diets with different forage:grain ratios and to quantify greenhouse gas (GHG) emissions from bedded manure packs in the eight feedlot pens holding these steers (14 head pen-1). Five animals (252 ± 20 kg) in each pen were randomly selected for measurement of CH4 emissions over the course of the 126-d feeding trial. Two 24-h gas collections were completed for each steer in each of three collection periods using the sulfur hexafluoride tracer gas technique. The fluxes of nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) from bedding packs were measured using vented static chambers in each sampling period. Methane production (L d-1) was 42% higher (P &lt; 0.05) from steers fed the low forage:grain ratio than from steers fed the high forage:grain ratio. Overall, methane production (% of gross energy intake) ranged from 0.9 to 6.9% on the low forage:grain diet and from 0.7 to 4.9% on the high forage:grain diet. Daily CH4 emissions were similar in the first two periods and increased during the third sampling period. There was no effect of diet on manure pack temperature during sampling, however, the manure pack was deeper (P &lt; 0.05) in pens holding animals fed the high forage:grain diet. Furthermore, diet had no effect on the manure pack fluxes. Total daily non-CO2 emissions from enteric and manure pack sources (CO2 equivalent) were different (P &lt; 0.05) between dietary treatments and averaged 1931 ± 81 g head-1 d-1 for the low forage:grain and 1394 ± 81 g head-1 d-1 for the high forage:grain diet. Key words: Feedlot steers, greenhouse gases, enteric fermentation, manure packs

Soil Gases and Temperatures: A Beef Cattle Feedlot Compared to Alfalfa

AbstractDry wells or caissons were used in an alfalfa field and at two locations in a feedlot pen to insert instrumentation and sampling devices to characterize the soil profiles. Soil gas compositions and temperatures studied for a 9‐yr period were strikingly dissimilar among the three sampling sites, yet each location had certain consistent properties unique to it. Two distinct areal‐wise soil‐zones had developed in the feedlot pen—one anaerobic and one aerobic. Only the anaerobic, feedbunk site produced methane (CH4). High soil carbon dioxide (CO2) and low oxygen (O2) contents were found there and at the pen center. Dinitrogen (N2) content at the feedbunk site was consistently less than in air which was attributed to a positive CO2 and CH4 pressure from biological sources. The main effects of location and year interacted with either depth or season for the common gases O2, N2, and CO2 at the three caisson sites. The main effects of depth, season, and year on O2 and CO2 were separated at the feedbunk site by excluding the other locations from data analysis. A first order interaction of season by year for N2 and CH4 showed the dependence of those gases on seasonal temperature change modified by years. A significant influence of the caissons on nearby soil temperature gradients was not detected. There were significant positive correlations between soil gas compositions and temperatures for CO2 at all locations and for CH4 at the feedbunk site. Soil N2 content was negatively correlated with soil temperature at both the feedbunk and center sites. These and other complementary results indicate that anaerobic soil conditions beneath a continuously‐maintained, intact, moist manure pack would minimize possible nitrate nitrogen (NO‐3‐N) formation and contamination of soil and groundwater.

Stratified Profiles: Characteristics of Simulated Soils in a Beef Cattle Feedlot

AbstractProfile combinations of clay loam, sand, clay loam over sand, and sand over clay loam were used to study salt movement and mineral nitrogen (N) transformations in a beef cattle feedlot. These soils were placed in lysimeters located in a feedlot stocked at the rate of one animal, weighing 270 to 450 kg, per 15.2 m2. The feedlot was bedded with sawdust and stocked continuously. After the lysimeters were in use 4 years, cores were removed for physical and chemical analyses. Each profile combination affected salt movement and mineral N transformations differently. Sand over clay loam was the superior combination to retard nitrate‐N (NO3‐‐N) movement and retain salt. In this configuration organic matter apparently moved from the manure pack through the sand along with NO3‐‐N and may have enhanced denitrification in the clay loam layer. The effect of location within the feedlot and depth increment within a given soil fill and their interaction were not important variables influencing profile chemical characteristics.

Time-Motion Analysis of Feedlot Manure Collection Systems

ABSTRACT MACHINE productivity, energy consumption and cost of feedlot manure collection were determined by time-motion analysis at four Texas cattle feedlots. Truck loading, hauling, and spreading time require-ments were also determined, as was the performance of wheel loader operators. The wheel loader/chisel plow combination produced the highest manure col-lection rate of 160 t (metric tons)/h (at 100 percent operating efficiency), followed in order by the ele-vating scraper, wheel loader, and wheel loader/roto-tiller. The most energy efficient collection system was the elevating scraper (0.88 kWh/t). Plowing of the manure pack before the wheel loader collection reduced overall energy consumption by 30 percent and increased the collection rate by 46 percent. The average rate of manure loading into spreader trucks was 186 t/h or 3.0 min per truck. Performance of wheel loader oper-ators varied by 85 percent. A prediction equation for spreader truck turn-around time versus haul distance was developed.

Chemical Composition of Feedlot Manure

AbstractManure samples were collected over a 10‐mo period from a feedlot with conventional pens and pens in which about one‐half the surface was covered with concrete. Samples were collected from the front, middle, and rear of each pen for each sampling period.The average percentages of 139 samples on a dry matter basis were: dry matter, 58.5; ash, 37.0; total N, 2.32; neutral detergent fiber, 45.9; acid detergent fiber, 39.7; hemicellulose, 6.29; cellulose, 9.78; lignin, 7.67; and ADF insoluble ash, 25.3. Average pH was 7.09. The average percentages on a dry matter basis for 63 manure samples were: P, 0.54; K, 1.35; Ca, 1.88; and Na, 0.51.Samples collected from concrete surfaces were 12.2% lower in ash because of less mising with soil. Effects of residence time of manure in the feedlot did not have a predictable effect upon composition because of the mixed influence of temperature, feedlot rations, and depth of the manure pack.