Kansas Feedlots Research Articles

36 Kansas State University Feedlot Boot Camp and Teaching Program: Growing Student Interest and Engagement in the Feedlot Industry

Abstract The Kansas State University Collegiate Feedlot Boot Camp and Teaching Program was initiated in January 2019 with the goal to develop student knowledge, skills, and professional relationships in feedlot management to help meet critical need for trained professionals in the feedlot industry. Allied industry supporters including feedlot nutrition and veterinary consultants, pharmaceutical companies, and lenders, as well as feedlot owners/managers and the Kansas State University Department of Animal Sciences and Industry collaborated to develop, sponsor, and offer the program, which is offered at no cost to students who are selected. Specific objectives are to train students in aspects of feedlot management through a 4-d comprehensive “Boot Camp” at Western Kansas feedlots, enhance students’ likelihood of participating in feedlot internships, and cultivate students’ vision of potential career paths within the industry. Boot Camp topics include cattle health, feeding and nutrition, feedlot design and maintenance, and the business of cattle feeding. A networking dinner brings students and feedlot managers together to facilitate students gaining internship and full-time employment with feedlots. Following the January Boot Camp, students share individual presentations on relevant industry topics. Presentations are recorded and shared with feedlot managers to further engagement between students and feedlot managers. Later in the spring semester students also participate in a half-day cattle processing experience at a feedlot near Kansas State to provide additional insight and experience with feedlot health management. Limited to 20 participants per year, 59 undergraduate students have completed the program. When surveyed, over 98% (58/59) of student participants agreed with the statement “My interest in pursuing an internship and (or) career in the feedlot industry grew as a result of this Boot Camp.” Approximately 50% of students participated in feedlot internships or earned full-time jobs working in feedlots. Ranging from students with little to no experience with feedlots to being raised on beef cow-calf or feedlot operations, progress is being made in growing student interest and awareness of career opportunities in the feedlot industry.

Bovine respiratory disease during the mid-portion of the feeding period: Observations of frequency, timing, and population from the field

The objective of this study is to provide observations related to bovine respiratory disease (BRD) in high-performing cattle during the mid-portion of the feeding period describing the occurrence, timing, and population. Data from a feedlot in Kansas were evaluated for temporal occurrence of BRD in high-performing and high-risk calves on a lot level. High-performing calves were categorized based on performance potential and carcass characteristics. High-risk calves were categorized based on administration of a macrolide at arrival processing. Cumulative incidence of BRD was evaluated within high-performing and high-risk categories. Models included the fixed effects of categorization (high performing and high risk), days on feed (DOF), and 2-way interaction between categorization and DOF and the random effect for repeated measures on individual lot. Additional data came from high-performing calves from Noble Research Institute cooperators’ cattle from 2 separate feedlots. The cumulative percentages of BRD for the high-performing and high-risk categories at 45 DOF were 33.7 and 67.2%, respectively. High-performing calves had BRD occurring later in the feeding period compared with high-risk calves. Cumulative BRD from the Noble Research Institute cooperators’ calves had an earlier onset of BRD morbidity compared with other high-performing cattle. Morbidity caused by BRD in high-performing cattle is greater than expected. Timing of BRD morbidity occurs at later DOF in high-performing calves compared with high-risk calves. Incidence for BRD occurred at ≥45 DOF in all 3 feedlots evaluated. Additional research is needed to identify potential causes for BRD morbidity during the mid-portion of the feeding period.

Description of feedlot animals culled for slaughter, revenue received, and associations with reported US beef market prices

Our objectives were to describe revenue received for feedlot cattle culled for slaughter and associations with reported weekly prices from US beef markets. Observational data on feedlot culls (N = 2,992) were collected from 4 Kansas feedlots over 2 years (2018 to 2020). Weekly prices from various US beef markets were used to evaluate correlations with prices received for culled animals. Descriptive statistics, and linear and generalized linear mixed models, were used to evaluate characteristics of feedlot culls. Musculoskeletal/trauma (49.7%) and respiratory disease (40.9%) were the most common reasons for culling. Culls returned revenue 98.1% of the time; those culled for respiratory disease or “other” reasons returned revenue significantly less frequently (96.7 or 96.3%, respectively) than those culled for musculoskeletal/trauma (99.1%). Mean revenue received [± 95% CI] was 434.81 [427.22 to 442.40] $/animal (culls returning no revenue included); and mean carcass price was 87.40 [86.70 to 88.10] $/hundredweight. Revenue was significantly correlated with several market indices, but most correlations were relatively weak. In this population, national cull cow (Breaker [75% lean]; over 500 lb [227 kg]) prices appeared to be the overall best indicator of feedlot cull prices, with feedlot cull carcasses averaging 74.6% of the weekly cull cow carcass price.

Estimating Herd-Scale Methane Emissions from Cattle in a Feedlot Using Eddy Covariance Measurements and the Carbon Dioxide Tracer Method.

Measurements of methane (CH) emissions from ruminants could provide invaluable data to reduce uncertainties in the global CH budget and to evaluate mitigation strategies to lower greenhouse gas emissions. The main objective of this study was to evaluate a new CO tracer (COT) approach that combined CH and CO atmospheric concentrations with eddy covariance (EC) CO flux measurements to estimate CH emissions from cattle in a feedlot. A closed-path EC system was used to measure CH and CO fluxes from a feedlot in Kansas. The EC flux measurements were scaled from landscape to animal scale using footprint analyses. Emissions of CH from the cattle were also estimated using the COT approach and measured CO and CH concentration, and scaled EC CO fluxes. The CH and CO concentration ratios showed a distinct diel trend with greater values during the daytime. Average monthly CH emission estimates using the COT approach ranged from 72 to 127 g animal d, which was consistent with the values reported in other studies that had similar animal characteristics. The COT method CH emission estimates showed good agreement with scaled CH EC fluxes (slope = 0.9 and = 0.8) for cold and dry months. However, the agreement between the two techniques was significantly reduced (slope = 1.5 and = 0.6) during wet and warm months. On average, the COT method CH emission estimates were 3% greater than the EC CH emissions. Overall, our results suggest that the COT method can be used to estimate enteric feedlot CH emissions.

Incidence of lameness and association of cause and severity of lameness on the outcome for cattle on six commercial beef feedlots.

OBJECTIVE To describe the incidence of specific causes of lameness and the associations of cause and severity of lameness on the outcome for cattle on commercial feedlots. DESIGN Dynamic population longitudinal study. ANIMALS Cattle on 6 commercial feedlots in Kansas and Nebraska during a 12-month period (mean daily population, 243,602 cattle; range, 223,544 to 252,825 cattle). PROCEDURES Feedlot personnel were trained to use a standardized diagnostic algorithm and locomotion score (LMS) system to identify and classify cattle by cause and severity of lameness. Information regarding lameness cause, severity, and treatments was recorded for individual cattle. Cattle were monitored until they left the feedlot (ie, outcome; shipped with pen mates [shipped], culled prematurely because of lameness [realized], or euthanized or died [died]). Incidence rates for various causes of lameness, LMSs, and outcomes were calculated. The respective associations of cause of lameness and LMS with outcome were evaluated. RESULTS Lameness was identified in 2,532 cattle, resulting in an overall lameness incidence rate of 1.04 cases/100 animal-years. Realized and mortality rates were 0.096 cattle/100 animal-years and 0.397 deaths/100 animal-years, respectively. Injury to the proximal portion of a limb was the most frequently identified cause of lameness followed by undefined lameness, septic joint or deep digital sepsis, and interdigital phlegmon (foot rot). As the LMS (lameness severity) at lameness detection increased, the percentage of cattle that died but not the percentage of cattle that were realized increased. CONCLUSIONS AND CLINICAL RELEVANCE Results provided clinically useful prognostic guidelines for management of lame feedlot cattle.

Determination of Particulate Matter Emissions from Cattle Feedlots Using Wind-Trax and the Flux-Gradient Technique

Large commercial cattle feedlots are significant sources of particulate matter (PM) emissions. This research compared WindTrax and the flux-gradient technique in estimating emissions of PM with aerodynamic diameter 10) from cattle feedlots. Meteorological conditions were measured and PM10 concentrations were profiled vertically (i.e., 2.0 to 7.62 m) at a large commercial beef cattle feedlot in Kansas from May through September 2011. Results show that between the two methods evaluated, WindTrax was least sensitive to changes in heights and number of heights used in the emission estimation, with calculated PM10 emission rates varying by up to 18% only. On the other hand, PM10 emission rates produced by the flux-gradient technique varied by almost 56% when changing either heights and/or number of heights in emission calculation. Both methods were sensitive to height settings, with their respective PM10 emission rates higher when the lowest height setting (2.0 m) was included. Calculating PM10 emission rates with the 7.62-m height led to lower estimates for the flux-gradient technique but no significant change in estimates was observed for WindTrax. As demonstrated in this study, for the flux-gradient technique, settings for the lowest and highest heights were the most critical in emission estimation; exclusion of other heights in between showed only to 2% to 6% change in calculated PM10 emission rates. In general, the higher PM10 emission rates were obtained with the flux-gradient technique. However, eliminating the lowest height (2.0 m) in the calculation and, at the same time, using a specific set of formulations for the flux-gradient technique made its calculated PM10 emission rates slightly lower (but not significantly different) than those from WindTrax.

TSP, PM10, and PM2.5 emissions from a beef cattle feedlot using the flux-gradient technique

Emissions data on air pollutants from large open-lot beef cattle feedlots are limited. This research was conducted to determine emissions of total suspended particulates (TSP) and particulate matter (PM10 and PM2.5) from a commercial beef cattle feedlot in Kansas (USA). Vertical particulate concentration profiles at the feedlot were measured using gravimetric samplers, and micrometeorological parameters were monitored with eddy covariance instrumentation during the nine 4- to 5-day intensive sampling campaigns from May 2010 through September 2011. Emission fluxes were determined from the measured concentration gradients and meteorological parameters using the flux-gradient technique. PM ratios based on calculated emission fluxes were 0.28 for PM2.5/PM10, 0.12 for PM2.5/TSP, and 0.24 for PM10/TSP, indicating that a large fraction of the PM emitted at the studied feedlot was in the coarse range of aerodynamic diameter, >10 μm. Median daily emission factors were 57, 21, and 11 kg 1000-head (hd)−1 d−1 for TSP (n = 20 days), PM10 (n = 19 days), and PM2.5 (n = 11 days), respectively. Cattle pen surface moisture contents of at least 20–30% significantly reduced both TSP and PM10 emissions, but moisture's effect on PM2.5 emissions was not established due to difficulty in measuring PM2.5 concentrations under low-PM conditions.

Particulate Emissions from a Beef Cattle Feedlot Using the Flux-Gradient Technique

Data on air emissions from open-lot beef cattle () feedlots are limited. This research was conducted to determine fluxes of particulate matter with an aerodynamic diameter ≤10 μm (PM) from a commercial beef cattle feedlot in Kansas using the flux-gradient technique, a widely used micrometeorological method for air emissions from open sources. Vertical PM concentration profiles and micrometeorological parameters were measured at the feedlot using tapered element oscillating microbalance PM samplers and eddy covariance instrumentations (i.e., sonic anemometer and infrared hygrometer), respectively, from May 2010 through September 2011, representing feedlot conditions with air temperatures ranging from -24 to 39°C. Calculated hourly PM fluxes varied diurnally and seasonally, ranging up to 272 mg m h, with an overall median of 36 mg m h. For warm conditions (air temperature of 21 ± 10°C), the highest hourly PM fluxes (range 116-146 mg m h) were observed during the early evening period, from 2000 to 2100 h. For cold conditions (air temperature of -2 ± 8°C), the highest PM fluxes (range 14-27 mg m h) were observed in the afternoon, from 1100 to 1500 h. Changes in the hourly trend of PM fluxes coincided with changes in friction velocity, air temperature, sensible heat flux, and surface roughness. The PM emission was also affected by the pen surface water content, where a water content of at least 20% (wet basis) would be sufficient to effectively reduce PM emissions from pens by as much as 60%.

Experimental research on the effects of water application on greenhouse gas emissions from beef cattle feedlots

The effect of water application (e.g., through rainfall or sprinkler system) on emissions of greenhouse gases (GHGs), such as nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2), from pen surfaces of open-lot beef cattle feedlots was evaluated under controlled laboratory conditions. Soil/manure samples were collected from several randomly selected pens from two beef cattle feedlots in Kansas and were used as simulated pen surfaces. Three treatments (i.e., dry and loose, moist and loose, and moist and compacted pen surface conditions) were considered, simulating surface conditions in the field after a typical rainfall event or water application with a sprinkler system. Soil/manure and water were mixed within glass containers and analyzed for GHG emission using a photo-acoustic infrared multi-gas analyzer; emission rates were calculated from measured concentrations. GHG emissions from the dry soil/manure samples were low, with mean values of 0.02, 0.00, and 45 mg m−2 h−1 for N2O, CH4, and CO2, respectively, compared to moist soil/manure samples. Water application on the dry manure samples resulted in large peaks of GHG fluxes, with peak values of 99.2, 28.6, and 15,443 mg m−2 h−1 for N2O, CH4, and CO2, respectively.

Nitrous Oxide Fluxes from a Commercial Beef Cattle Feedlot in Kansas

Emission of greenhouse gases, including nitrous oxide (N2O), from open beef cattle feedlots is becoming an environmental concern; however, research measuring emission rates of N2O from open beef cattle feedlots has been limited. This study was conducted to quantify N2O emission fluxes as affected by pen surface conditions, in a commercial beef cattle feedlot in the state of Kansas, USA, from July 2010 through September 2011. The measurement period represented typical feedlot conditions, with air temperatures ranging from -24 to 39°C. Static flux chambers were used to collect gas samples from pen surfaces at 0, 15, and 30 minutes. Gas samples were analyzed with a gas chromatograph and from the measured concentrations, fluxes were calculated. Median emission flux from the moist/muddy surface condition was 2.03 mg m−2 hour−1, which was about 20 times larger than the N2O fluxes from the other pen surface conditions. In addition, N2O peaks from the moist/muddy pen surface condition were six times larger than emission peaks previously reported for agricultural soils.

Particulate Emissions from a Beef Cattle Feedlot Using the Flux-Gradient Technique

Data on air emissions from open-lot beef cattle () feedlots are limited. This research was conducted to determine fluxes of particulate matter with an aerodynamic diameter ≤10 μm (PM) from a commercial beef cattle feedlot in Kansas using the flux-gradient technique, a widely used micrometeorological method for air emissions from open sources. Vertical PM concentration profiles and micrometeorological parameters were measured at the feedlot using tapered element oscillating microbalance PM samplers and eddy covariance instrumentations (i.e., sonic anemometer and infrared hygrometer), respectively, from May 2010 through September 2011, representing feedlot conditions with air temperatures ranging from -24 to 39°C. Calculated hourly PM fluxes varied diurnally and seasonally, ranging up to 272 mg m h, with an overall median of 36 mg m h. For warm conditions (air temperature of 21 ± 10°C), the highest hourly PM fluxes (range 116-146 mg m h) were observed during the early evening period, from 2000 to 2100 h. For cold conditions (air temperature of -2 ± 8°C), the highest PM fluxes (range 14-27 mg m h) were observed in the afternoon, from 1100 to 1500 h. Changes in the hourly trend of PM fluxes coincided with changes in friction velocity, air temperature, sensible heat flux, and surface roughness. The PM emission was also affected by the pen surface water content, where a water content of at least 20% (wet basis) would be sufficient to effectively reduce PM emissions from pens by as much as 60%.

Comparison of AERMOD and WindTrax dispersion models in determining PM10 emission rates from a beef cattle feedlot

Reverse dispersion modeling has been used to determine air emission fluxes from ground-level area sources, including open-lot beef cattle feedlots. This research compared Gaussian-based AERMOD, the preferred regulatory dispersion model of the U.S. Environmental Protection Agency (EPA), and WindTrax, a backward Lagrangian stochastic-based dispersion model, in determining PM10 emission rates for a large beef cattle feedlot in Kansas. The effect of the type of meteorological data was also evaluated. Meteorological conditions and PM10 concentrations at the feedlot were measured with micrometeorological/eddy covariance instrumentation and tapered element oscillating microbalance (TEOM) PM10 monitors, respectively, from May 2010 through September 2011. Using the measured meteorological conditions and assuming a unit emission flux (i.e., 1 µg/m2-sec), each model was used to calculate PM10 concentrations (referred to as unit-flux concentrations). PM10 emission fluxes were then back-calculated using the measured and calculated unit-flux PM10 concentrations. For AERMOD, results showed that the PM10 emission fluxes determined using the two different meteorological data sets evaluated (eddy covariance-derived and AERMET-generated) were basically the same. For WindTrax, the two meteorological data sets (sonic anemometer data set, a three-variable data set composed of wind parameters, surface roughness, and atmospheric stability) also produced basically the same PM10 emission fluxes. Back-calculated emission fluxes from AERMOD were 32 to 69% higher than those from WindTrax. Implications This work compared the PM10 emission rates determined from a large commercial cattle feedlot in Kansas by reverse dispersion modeling using AERMOD and WindTrax. Emission fluxes derived from AERMOD were greater than those from WindTrax by mean factors of 1.3 to 1.6. Based on the high linearity observed between the two models, emission fluxes derived from one dispersion model for the purpose of simulating dispersion could be applied to the other model using appropriate conversion factors.

Laboratory evaluation of surface amendments for controlling greenhouse gas emissions from beef cattle feedlots

Pen surface amendments for mitigating emissions of greenhouse gases (GHGs), such as nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2), from beef cattle feedlots, were evaluated under controlled laboratory conditions. Amendments were organic residues (i.e., sorghum straw, prairie grass, woodchip), biochar from those organic residues and from beef cattle manure, and activated carbon. Manure samples were collected from several randomly selected pens from two beef cattle feedlots in Kansas and used in the experiments, either as dry (0.10 g · g−1 wet basis water content) or moist (0.35 g · g−1 wet basis). For each amendment, four different treatment levels (i.e., amounts of material) were placed on top of manure samples in glass containers and analyzed for GHG emissions using a photo-acoustic infrared multi-gas analyzer. From measured concentrations, emission rates were determined. For the dry manure conditions, all amendment materials showed significant reduction of N2O and CO2 emissions compared to the control (i.e., no amendment). For the moist manure conditions, none of the amendments showed significant effects on GHG emissions during the first 8 days; at days 10 and 15 after application, however, the biochar materials performed significantly better than the control (i.e., no surface amendment) in reducing N2O and CH4 emissions. No significant difference was observed in GHG emissions when the amendments were placed on top or mixed within the top surface layer of the manure.

Particulate matter emission rates from beef cattle feedlots in Kansas—Reverse dispersion modeling

Open beef cattle feedlots emit various air pollutants, including particulate matter (PM) with equivalent aerodynamic diameter of 10 μm or less (PM10); however, limited research has quantified PM10 emission rates from feedlots. This research was conducted to determine emission rates of PM10 from large cattle feedlots in Kansas. Concentrations of PM10 at the downwind and upwind edges of two large cattle feedlots (KS1 and KS2) in Kansas were measured with tapered element oscillating microbalance (TEOM) PM10 monitors from January 2007 to December 2008. Weather conditions at the feedlots were also monitored. From measured PM10 concentrations and weather conditions, PM10 emission rates were determined using reverse modeling with the American Meteorological Society/U.S. Environmental Protection Agency Regulatory Model (AERMOD). The two feedlots differed significantly in median PM10 emission flux (1.60 g/m2-day for KS1 vs. 1.10 g/m2-day for KS2) but not in PM10 emission factor (27 kg/1000 head-day for KS1 and 30 kg/1000 head-day KS2). These emission factors were smaller than published U.S. Environmental Protection Agency (EPA) emission factor for cattle feedlots. Implications This work determined PM10 emission rates from two large commercial cattle feedlots in Kansas based on extended measurement period for PM10 concentrations and weather conditions, and reverse dispersion modeling, providing baseline information on emission rates for cattle feedlots in the Great Plains that could be used for improving emissions estimates. Within the day, PM emission rates were generally highest during the afternoon period; PM emission rates also increased during early evening hours. In addition, PM emission rates were highest during warm season and prolonged dry periods. Particulate control measures should target those periods with high emission rates.

Concentrations of Particulate Matter Emitted from Large Cattle Feedlots in Kansas

ABSTRACT Particulate matter (PM) emitted from cattle feedlots are thought to affect air quality in rural communities, yet little is known about factors controlling their emissions. The concentrations of PM (i.e., PM2.5, PM10, and total suspended particulates or TSP) upwind and downwind at two large cattle feedlots (KS1, KS2) in Kansas were measured with gravimetric samplers from May 2006 to October 2009 (at KS1) and from September 2007 to April 2008 (at KS2). The mean downwind and net (i.e., downwind − upwind) mass concentrations of PM2.5, PM10, and TSP varied seasonally, indicating the need for multiple-day, seasonal sampling. The downwind and net concentrations were closely related to the moisture content of the pen surface. The PM2.5/PM10 and PM2.5/TSP ratios at the downwind sampling location were also related to the moisture content of the pen surface, humidity, and temperature. Measurement of the particle size distribution downwind of the feedlot with a cascade impactor showed geometric mean diameter ranging from 7 to 18 μm, indicating that particles that were emitted from the feedlots were generally large in size. IMPLICATIONS This work characterized the total suspended particulates (TSP), PM10, and PM2.5 concentrations emitted from large cattle feedlots in Kansas, providing baseline information on concentrations and size distribution of particulates emitted from feedlots in the Great Plains. As expected, high dust events were observed during the spring and summer; dust control strategies should target those potential dust events. PM emitted from the feedlots was dominated by coarse particles; as such, development and evaluation of dust control strategies, including water sprinkling, shelterbelts, etc., might have to focus more on the coarse particles. The moisture content of the pen surface was one of the most significant factors affecting PM concentrations in cattle feedlots; by controlling the moisture content, it would be possible to control dust emissions.

Particulate Control Efficiency of a Water Sprinkler System at a Beef Cattle Feedlot in Kansas

Water sprinkler systems are one method for controlling particulate matter (PM) emissions from cattle feedlots; however, limited data are available on the efficiency of these systems. This research was conducted to determine the PM control efficiency of a water sprinkler system in a cattle feedlot in Kansas. Downwind and upwind PM10 concentrations at the feedlot (KS1) were monitored with tapered element oscillating microbalance (TEOM) PM10 monitors from January 2006 to July 2009. The feedlot was equipped with a sprinkler system with a maximum water application rate of 5.0 mm d-1 (5.0 L m-2 d-1). Control efficiency was determined by considering the PM10 data during sprinkler on/off events (i.e., the sprinkler system was operated for at least one day and was either followed or preceded by at least one day of no water sprinkling). Control efficiency equaled the percentage reduction in net PM10 concentration (i.e., downwind concentration - upwind concentration). PM10 control efficiency ranged from 32% to 80% with an overall mean of 53% (based on 24 h PM10 values). The effect of the sprinkler system in reducing net PM10 concentration lasted for one day or less. The PM10 concentration percentage reduction due to rainfall events was also determined at feedlot KS1 and at another feedlot (KS2). Feedlot KS2, located less than 40 km from KS1, was not equipped with a sprinkler system but practiced more frequent pen cleaning. Percentage reductions in net PM10 concentrations due to rainfall events were mostly in the range of 60% to almost 100% for both feedlots, with overall means of 77% for KS1 and 76% for KS2. The effects of rainfall events (with rainfall amounts >10 mm per event) lasted for 3 to 7 days depending on rainfall amount and intensity.

Measuring Cattle Feedlot Dust Using Laser Diffraction Analysis

Considerable amounts of particulate matter (PM), including total suspended particulates (TSP), particulates with equivalent aerodynamic diameter less than or equal to 10 m (PM10), and particulates with equivalent aerodynamic diameter less than or equal to 2.5 m (PM2.5), are emitted from large beef cattle feedlots. Particle size distribution and concentrations of TSP, PM10, and PM2.5 at a commercial cattle feedlot in Kansas were measured over a two-year period. The feedlot had a capacity of 30,000 head with a total pen area of 50 ha and was equipped with a sprinkler system for dust control. Collocated low-volume samplers for TSP, PM10, and PM2.5 were used to measure concentrations of TSP, PM10, and PM2.5 at the upwind and downwind edges of the feedlot. A laser diffraction (LD) analyzer (Beckman Coulter LS 13 320) was utilized to determine the particle size distribution of dust samples collected by TSP samplers. A micro-orifice uniform deposit impactor (MOUDI) was also used to measure particle size distribution at the downwind edge of the feedlot. Considering the same effective size range, the LD analyzer and MOUDI did not differ significantly in mean geometric mean diameter (GMD) (11.6 vs. 13.0 m) and in mean geometric standard deviation (2.3 vs. 2.3). Wind speed and period of sampling significantly affected the mean GMD of the particles. The PM10 and PM2.5 concentrations that were calculated from the LD method and TSP data were not significantly different from those measured by low-volume PM10 and PM2.5 samplers (122 vs. 131 g m-3 for PM10 and 26 vs. 35 g m-3 for PM2.5). Both PM10 and PM2.5 fractions decreased as pen surface water content increased, but the PM2.5/PM10 ratio showed little change as pen surface water content increased.

Length of weaning period but not timing of vaccination affects feedlot receiving performance and health of fall-weaned, ranch-direct beef calves

Weaning and preconditioning programs are thought to be crucial to calf health and performance during the finishing period. The stress of maternal separation, changes in diet, environmental changes, and exposure to unfamiliar pathogens increase susceptibility of recently weaned calves to bovine respiratory disease. Vaccination programs are implemented near weaning to decrease the incidence of respiratory disease. Many vaccination strategies are practiced by cow-calf producers in the United States. The most cautious strategy involves vaccination against respiratory disease pathogens 2 to 4 weeks before maternal separation followed by a booster at weaning. This strategy is used in instances in which time, labor, and facilities are available to gather and process calves while they are still suckling. Another common strategy is to defer vaccination until after calves have been shipped to a feedlot. Deferring vaccination until arrival in feedlots is thought to increase incidence of respiratory disease compared with vaccination programs implemented at the ranch of origin. This assumption has not been widely scrutinized for native Kansas cattle that are finished in Kansas feedlots.

Evaluation of metaflumizone granular fly bait for management of houseflies

The housefly, Musca domestica L. (Diptera: Muscidae), is a pest of great veterinary and public health importance. In this study, the efficacy of metaflumizone granular fly bait was assessed on first generation (F1) housefly adults raised from flies collected at a cattle feedlot in Kansas. All bioassays were conducted as choice tests, with flies having ad libitum access to water, granular sugar and bait. A commercial methomyl-based bait (Golden Malrin) was used as positive control; no bait (water and granular sugar only) was used as negative control. Fly mortality was recorded on days 2, 7 and 14. The metaflumizone bait was significantly more slow-acting than the methomyl bait (mortality rates after 2 days of exposure were 49.9% and 57.9%, respectively). However, there were no significant differences in cumulative mortality later in the bioassays. Cumulative mortality rates on days 7 and 14 were 96.1% (metaflumizone), 91.4% (methomyl) and 99.0% (metaflumizone), 97.6% (methomyl), respectively. Our results demonstrate that the metaflumizone granular fly bait may be an effective modality for incorporation into management programmes for houseflies in and around livestock production facilities as well as in residential settings.

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.