Open-lot Beef Research Articles

Field Comparison of PM10 Samplers

Fugitive emissions of PM10 (particulate matter with equivalent aerodynamic diameter of 10 µm or less) are an increasing concern for concentrated animal feeding operations, including open-lot beef cattle feedlots. Various federal reference method (FRM) and equivalent samplers can be used to measure PM10 concentrations. This research compared the performance of Tapered Element Oscillating Microbalance™ (TEOM), FRM high-volume (HV), and low-volume (LV) PM10 samplers in measuring PM10 concentrations in the vicinity of large cattle feedlots in Kansas. Each of the three samplers was installed at the downwind and upwind perimeters of two commercial cattle feedlots (KS1 and KS2). Samplers were operated from May 2006 to February 2008 at KS1 and from February 2007 to February 2008 at KS2. PM10 concentration ranged from <10 to 832 µg m-3 at KS1 and from <10 to 713 µg m-3 at KS2. Comparison of collocated PM10 samplers showed that measured PM10 concentration was generally largest with the TEOM PM10 sampler and smallest with the LV PM10 sampler. Differences in PM10 concentration among samplers were affected by location and duration of sampling, season, and slightly by weather conditions.

Ammonia emissions from a beef cattle feedyard on the southern High Plains

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.

Characteristics of Manure Harvested from Beef Cattle Feedlots

Open lot cattle production systems present unique challenges for nutrient planning processes. Previous estimates of quantities and characteristics of harvested manure from this type of facility are based upon data from the early 1970s. In addition, harvested manure is impacted by weather, feeding program, season, and pen management decisions. The objectives of this study are to characterize under commercial conditions for open lot beef systems: 1) harvested manure quantities and characteristics; 2) impact of factors such as feeding program, season, and management on harvested manure; and 3) mass balance for nitrogen (N) and phosphorus (P). Data from six commercial feedlots (representing 6,366 head of cattle) suggest that 33% of excreted N (65 g/hd/d) and 91% of excreted P (32 g/hd/d) are harvested as manure on average and that current standard estimates published by ASAE (2005) and NRCS (1992a) overestimate harvested manure N and P. Additionally, significant variation was observed among feedlots. This variation is driven by ration nutrient concentration (P only), pen conditions prior to and during manure harvest (N and P), and management choices relative to use of manure in lot maintenance (N and P). The variation would suggest that nutrient planning estimates for open lots would need to be based upon farm specific data as opposed to typical or standard values. Finally, a pen-based mass nutrient balance for a beef cattle feedlot suggests that pen outputs as finished animal, harvested manure, and nutrient losses represent 31%, 23%, and 47%, respectively, of all pen N inputs and 38%, 57%, and 5%, respectively, of all pen P inputs. Inputs include nutrient content of all animals and feed entering a feedlot pen over a grow-out period.

ODOR CHARACTERIZATION AT OPEN-LOT BEEF CATTLE FEEDYARDS USING TRIANGULAR FORCED-CHOICE OLFACTOMETRY

Odor is a growing concern at concentrated animal feeding operations as residential houses encroach upon ruralareas once occupied only by agriculture. A research project was conducted to determine baseline ambient odor characteristicsat large open-lot beef cattle feedyards and to develop a better understanding of when and why odors occur at feedyards.Ambient odor samples were collected two to four times per month over a 12-month period in 2002-2003 at three largecommercial open-lot beef cattle feedyards in the Texas panhandle. Ambient odor samples were collected upwind of thefeedyard, downwind of the pens, and downwind of the runoff storage pond. Odor samples were also collected on five separatedays covering four months in 2004 from a surface isolation flux chamber to estimate odor emission rates from the feedyardsurface. All odor samples were collected in 10 L Tedlar bags and analyzed with trained human odor panelists for odorconcentration (detection threshold, DT) by dynamic dilution forced-choice olfactometry, intensity by reference scaling, andhedonic tone. Manure moisture content and weather data were collected on-site at each of the feedyards. At two of thefeedyards, mean DTs downwind of the pens and storage pond were statistically similar to upwind DTs, ranging from 33 to45 OU m-3. At the third feedyard, mean DTs downwind of the pens (69 OU m-3) and pond (124 OU m-3) were statisticallyhigher than the mean upwind DT (36 OU m-3) (p < 0.05). Odor emission rates ranged from 0.3 to 3.2 OU m-2 s-1 during aperiod when downwind DTs ranged from 17 to 132 OU m-3. A number of elevated DTs were explained by elevated manuremoisture contents from recent precipitation. These results demonstrate that odor production from open-lot beef cattlefeedyards is a complex phenomenon that depends at least partially on weather conditions. Thus, odor prediction and controlwill likely be difficult at these facilities.

ENGINEERING PROPERTIES AND ECONOMICS OF SOIL CEMENT FEEDYARD SURFACING

Hard surfacing is being evaluated by open-lot beef cattle feedyard owners as a means to increase animal performance and improve manure quality. Soil cement, a compacted mixture of soil and Portland cement, has been used successfully for surfacing roads and airports. In this research, the engineering properties of soil cement and associated economics were evaluated using Amarillo fine sandy loam, one of the most common granular soils in the Texas Panhandle region. Soil cement specimens were prepared in compaction molds to determine the optimum moisture content and cement content for compaction. Specimens were subjected to simulated field conditions including exposure to manure for nine months. Specimens were then subjected to a series of tests: unconfined compressive strength, freezing-thawing, and wetting-drying. Unconfined compressive strength of soil cement increased linearly with cement content between 5% and 20% (R2 = 0.99). At a cement content of 7.5%, the specimens disintegrated when exposed to field conditions for nine months, while the specimens at 15% cement remained intact. Exposure to manure for nine months did not affect unconfined compressive strength or mass lost during freezing-thawing and wetting-drying. The estimated total cost for installing a 15 cm thick soil cement surface was $582 per 100 m2. The annual breakeven cost at a discount rate of 8% and payback period of five years was $146 per 100 m2. Potential annual feed conversion benefits of $330 per 100 m2 were estimated based on previous research, leaving soil cement an economically feasible option for further research and application.

SURFACE AMENDMENTS TO MINIMIZE AMMONIA EMISSIONS FROM BEEF CATTLE FEEDLOTS

Amendments for reducing ammonia emissions from open–lot beef cattle feedlots were evaluated in the laboratory. A mixture of 1550 g of soil, 133 g of feces, and 267 g of urine was placed into plastic containers that were 20 cm U 20 cm U 12 cm deep. Using a vacuum system, clean air (3.2 L/min) was passed over the soil–manure surface and ammonia was trapped by bubbling the air through dilute sulfuric acid. Treatments were a blank (soil with no manure), control (soil–manure mixture with no amendment), 4500 kg/ha Al2(SO4)3 (alum), 9000 kg/ha alum, 375 kg/ha commercial product (CP) for reducing ammonia emissions, 750 kg/ha CP, 4500 kg/ha calcium chloride (CaCl2), 9000 kg/ha CaCl2, 9000 kg/ha brown humate, 9000 kg/ha black humate, 1 kg/ha of the urease inhibitor N–(n–butyl) thiophosphoric triamide (NBPT), and 2 kg/ha NBPT. There were four replications of each treatment. Ammonia emissions were measured for 21 days following application of the amendments. Cumulative ammonia emissions after 21 days, expressed as a percentage of the control, were 0.4% for the blank, 8.5% for 4500 kg/ha alum, 1.7% for 9000 kg/ha alum, 73.6% for 375 kg/ha CP, 68.2% for 750 kg/ha CP, 28.8% for 4500 kg/ha CaCl2, 22.5% for 9000 kg/ha CaCl2, 32.4% for 9000 kg/ha brown humate, 39.8% for 9000 kg/ha black humate, 35.9% for 1 kg/ha NBPT, and 34.4% for 2 kg/ha NBPT. Calculated costs of the amendments ranged from $0.12 to $5.53 per application per head. Only one treatment had a benefit/cost ratio greater than 1.0. Results suggest that amendments can reduce ammonia emissions from open feedlots, but the costs may be prohibitive. Site–specific environmental impacts should be evaluated before using these amendments in a commercial setting.