Beef Cattle Feedyards Research Articles

Daily, Monthly, Seasonal, and Annual Ammonia Emissions from Southern High Plains Cattle Feedyards

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 (<15 kg ha d) during the winter. Mean monthly per capita emission rate (PCER) of NH-N at one feedyard ranged from 31 g NH-N head d (January) to 207 g NH-N head d (October), when increased dietary crude protein from wet distillers grains elevated emissions. Ammonia N emissions at the other feedyard ranged from 36 g NH-N head d (January) to 121 g NH-N head d (September). Monthly fractional NH-N loss ranged from a low of 19 to 24% to a high of 80 to 85% of fed N at the two feedyards. Seasonal PCER at the two feedyards averaged 60 to 71 g NH-N head d during winter and 103 to 158 g NH-N head d during summer. Annually, PCER was 115 and 80 g NH-N head d at the two feedyards, which represented 59 and 52% of N fed to the cattle. Detailed studies are needed to determine the effect of management and environmental variables such as diet, temperature, precipitation, and manure water content on NH emissions.

Effect of Urease Inhibitor Application Rate and Rainfall on Ammonia Emissions from Beef Manure

Social, economic, and environmental factors have prompted the desire to reduce global atmospheric ammonia emissions. A research project was conducted to assess the efficacy of the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) for reducing ammonia emissions from simulated open-lot beef cattle feedyard surfaces. A mixture of beef cattle feces and urine (manure) was placed into small emission chambers (167 167 170 mm deep). A urea solution was added every 2 days to simulate continual urine deposition in the feedyard. Clean air (1.4 L min-1) was passed over the manure surface, and ammonia was trapped in an acid solution. The six treatments (three replications per treatment) included combinations of NBPT application rate with or without simulated rainfall. NBPT was applied at zero, steady (5 kg ha-1 every 4 days), or increasing (5 kg ha-1 initially, doubled every 4 days up to 40 kg ha-1) rates. Rainfall treatments received 6 mm every 4 days. For all treatments, mean ammonia emissions from the manure were lower (p < 0.05) when simulated rainfall was added. Mean ammonia emission rates for the NBPT treatments were 26% to 33% of the non-NBPT treatments, demonstrating that NBPT was effective at reducing emissions from the manure surfaces in both wet and dry conditions. There were no statistical differences in mean ammonia emission rates for the steady and increasing NBPT application rates, showing that a steady NBPT application of 5 kg ha-1 every 4 days was effective in reducing ammonia emissions from the manure. The use of NBPT appears promising for reducing ammonia emissions at beef cattle feedyards. Additional research is warranted to study the effectiveness under long-term conditions in an outdoor feedyard setting.

Continuous Ammonia Emission Measurements from a Commercial Beef Feedyard in Texas

Ammonia emissions from cattle feedlots pose the potential to react with other compounds such as oxides of nitrogen and sulfur, which lead to detrimental environmental effects. Ambient ammonia (NH3) concentrations were measured continuously at a beef cattle feedyard for 12 months beginning in March 2007. Concentrations were measured every 5 min, 24 hours per day, at a sample intake height of 3.3 m using a chemiluminescence analyzer. On-site weather data were collected concurrently. Modeled emissions of NH3 were compared with the mass balance of N for the feedyard. Mean annual NH3 concentrations were 0.57 ppm, with a monthly average low of 0.37 ppm in December 2007 and a monthly average high of 0.77 ppm in August 2007. Flux densities were calculated using a backward Lagrangian stochastic model (WindTrax 2.0.7.8). Mean annual flux density was 70.7 g m-2 s-1 (2.2 kg m-2 year-1). Mean monthly flux density ranged from 42.7 to 123.1 g m-2 s-1 (0.11 to 0.32 kg m-2 month-1) in November and April 2007, respectively. Both concentration and flux density had a diel distribution with minima during the nighttime hours and maxima during the early afternoon. On an annual basis, 48.8% of fed N was volatilized as NH3. The inverse modeled daily ammonia production per head was 85.3 g NH3-N (head fed)-1 d-1.

Chemical Composition of Pen Surface Layers of Beef Cattle Feedyards

The biological, physical, and chemical characteristics of beef cattle feedyard pen surfaces may affect nutrient transformations and losses to the atmosphere, ground water, or surface water. Feedyard pen surfaces can typically segregate into 3 or 4 layers. The purpose of this study was to determine if there were seasonal, within-pen location, days-on-feed, or urine effects on the chemical composition of the pen surface layers of feedyards. Samples were collected from 5 locations in 9 pens at 3 feedyards in each season and were analyzed for gravimetric water, pH, electrical conductivity (EC), nitrate + nitrite-N (NOx-N), ammonia + ammonium-N (NHx-N), N, C, and P. The percentage of water increased (P < 0.01) with depth among the manure layers and decreased in the soil. The pH of the manure layers increased with depth (P < 0.01) from approximately 7.6 to 8.2. The EC of the manure layers was greater (P < 0.01) than the EC of the soil layer, whereas the NOx-N concentration was greater (P < 0.01) in the soil layer. The NHx-N concentrations were lowest in the soil layer (P < 0.01). Total C and N concentrations decreased (P < 0.01) with sample depth. The composition of the layers was affected by season and location within the pen. Recent urine deposition did not affect the lower layers. The NHx-N concentration of the layers increased with days on feed. The differences in the chemical and physical properties of the layers in a feedlot pen may potentially affect nutrient losses to the atmosphere and to groundwater.

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.

Soil nitrogen distribution and deposition on shortgrass prairie adjacent to a beef cattle feedyard

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.

Multidimensional Gas Chromatography−Olfactometry for the Identification and Prioritization of Malodors from Confined Animal Feeding Operations

Odor profiling efforts were directed at applying to high-density livestock operations some of the lessons learned in resolving past, highly diverse, odor-focused investigations in the consumer product industry. Solid-phase microextraction (SPME) was used for field air sampling of odorous air near and downwind of a beef cattle feedyard and a swine finisher barn in Texas. Multidimensional gas chromatography-olfactometry (MDGC-O) was utilized in an attempt to define and prioritize the basic building blocks of odor character associated with these livestock operations. Although scores of potential odorant volatiles have been previously identified in high-density livestock operations, the odor profile results developed herein suggest that only a very few of these may constitute the preponderance of the odor complaints associated with these environments. This appeared to be especially true for the case of increasing distance from both cattle feedyard and swine barn facilities, with p-cresol consistently taking on the dominant odor impact role with ever increasing distance. In contrast, at- or near-site odor profiles were shown to be much more complex, with many of the well-known lower tier odorant compounds rising in relative significance. For the cattle feedyard at- or near-site odor profiles, trimethylamine was shown to represent a significantly greater individual odor impact relative to the more often cited livestock odorants such as hydrogen sulfide, the organic sulfides, and volatile fatty acids. This study demonstrates that SPME combined with a MDGC-O-mass spectrometry system can be used for the sampling, identification, and prioritization of odors associated with livestock.

Influence of dietary crude protein concentration and source on potential ammonia emissions from beef cattle manure1,2,3

Emissions of ammonia, as well as other gases and particulates, to the atmosphere are a growing concern of livestock producers, the general public, and regulators. The concentration and ruminal degradability of CP in beef cattle diets may affect urinary and fecal excretion of N and thus may affect ammonia emissions from beef cattle feed yards. To determine the effects of dietary CP concentration and degradability on potential ammonia emissions, 54 steers were randomly assigned to nine dietary treatments in a 3 x 3 factorial arrangement of treatments. Treatments consisted of three dietary CP concentrations (11.5, 13, and 14.5%) and three supplemental urea:cottonseed meal ratios (100:0, 50:50, and 0:100 of supplemental N). Steers were confined to tie stalls, and feces and urine excreted were collected and frozen after approximately 30, 75, and 120 d on feed. One percent of daily urine and feces excretion were added to polyethylene chambers containing 1,550 g of soil. Chambers were sealed, and ammonia emissions were trapped in an acid solution for 7 d using a vacuum system. As the protein concentration in the diet increased from 11.5 to 13%, in vitro daily ammonia emissions increased (P < 0.01) 60 to 200%, due primarily to increased urinary N excretion. As days on feed increased, in vitro ammonia emissions also increased (P < 0.01). Potential ammonia losses were highly correlated (P < 0.01) to urinary N (r2 = 0.69), urinary urea-N (r2 = 0.58) excretion, serum urea-N concentration (r2 = 0.52), and intake of degradable protein N (r2 = 0.23). Although dietary composition can affect daily ammonia losses, daily ammonia emissions must be balanced with effects on animal performance to determine optimal protein concentrations and forms in the diet.

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.

RATE AND FREQUENCY OF UREASE INHIBITOR APPLICATION FOR MINIMIZING AMMONIA EMISSIONS FROM BEEF CATTLE FEEDYARDS

Reduction of ammonia emissions from animal feeding operations is important from the perspective of environmental policy and its impact on agriculture. A laboratory study was conducted to evaluate how rate and frequency of urease inhibitor application affect ammonia emissions from simulated beef cattle feedyard manure surfaces. The urease inhibitor N-(n-butyl)thiophosphoric triamide (NBPT) was applied at rates of 0, 1, and 2 kg ha-1, at 8, 16, and 32 day frequencies, and with or without simulated rainfall. Synthetic urine was added every two days to the manure surface. Gaseous ammonia was trapped by bubbling through 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 NBPT ha-1 treatments resulting in 49% to 69% reduction in ammonia emission rates, respectively. The 8-day, 1 kg NBPT ha-1 treatments had the most promising benefit/cost ratios of 0.48 to 0.60. Simulated rainfall reduced the ammonia emission rates from 1% to 25% as compared to the non-rainfall treatments, although the differences were not statistically different. The use of NBPT for reducing ammonia emissions looks promising; however, possible buildup of urea in the pen surface may require a higher NBPT application rate with time.

Vegetation, phosphorus, and dust gradients downwind from a cattle feedyard

A native shortgrass pasture downwind from a 25,000-head beef cattle feedyard near Bushland, Tex. degraded after the feedyard was stocked in 1970. Objectives were to determine pre-1970 vegetation, quantify current vegetation, and describe changes in vegetation, soil P and dust deposition with distance from the feedyard. Pre-1970 vegetation was documented with published measurements. In 2000, plant cover was quantified using 600 quadrats. Soil P, conserved in the local soil, was measured in soil samples from 119 locations. Dust was collected at 12 locations. From 1966‐1972, cover was 18.8% blue grama [Bouteloua gracilis (H.B.K.) Lag. ex Griffiths] and 7.4% buffalograss [Buchloe dactyloides (Nutt.) Engelm.]; the 2 species comprised 95% of vegetation cover. In 2000, perennial grass (75‐99% blue grama) cover averaged 3.7% at 525 m from the feedyard. Conversely, annual grass (67% Hordeum pusillum Nutt.) and annual forb [72% Kochia scoparia (L.) Schrad.] covers were 49% and 35% nearest the feedyard and decreased to 9% and 1%, respectively, at > 525 m. Over a similar distance, soil P decreased from 75 to 17 mg kg -1 . Dust deposition rate decreased with distance from the feedyard. Manure dust contribution to total dust ranged from negligible to 89%. It was estimated that 20‐30 kg N ha -1 year -1 were deposited over 30 years to areas nearest the feedyard. Changes in vegetation and soil P were greatest at 500 m downwind from the feedyard. The pattern of vegetation, soil fertility, and dust deposition gradients strongly suggested that the feedyard was the primary cause of the observed changes, although a direct causal link could not be established, and other factors, such as grazing, could have contributed to the observed changes. The High Plains region of the Texas Panhandle and surrounding states is a mosaic of irrigated and dry cropland and grassland. More than half the agricultural land area is grassland, and most of that is native rangeland. Shortgrass prairie dominates most native rangeland, especially on upland clay and silty clay soils. Blue grama [Bouteloua gracilis (H.B.K.) Lag. ex Griffiths] and buffalograss [Buchloe dactyloides (Nutt.) Engelm.] are the major

Vegetation, phosphorus, and dust gradients downwind from a cattle feedyard

A native shortgrass pasture downwind from a 25,000-head beef cattle feedyard near Bushland, Tex. degraded after the feedyard was stocked in 1970. Objectives were to determine pre-1970 vegetation, quantify current vegetation, and describe changes in vegetation, soil P and dust deposition with distance from the feedyard. Pre-1970 vegetation was documented with published measurements. In 2000, plant cover was quantified using 600 quadrats. Soil P, conserved in the local soil, was measured in soil samples from 119 locations. Dust was collected at 12 locations. From 1966-1972, cover was 18.8% blue grama [Bouteloua gracilis (H.B.K.) Lag. ex Griffiths] and 7.4% buffalograss [Buchloe dactyloides (Nutt.) Engelm.]; the 2 species comprised 95% of vegetation cover. In 2000, perennial grass (75-99% blue grama) cover averaged 3.7% at &lt; 150 m from the feedyard, and increased to 28% at &gt; 525 m from the feedyard. Conversely, annual grass (67% Hordeum pusillum Nutt.) and annual forb [72% Kochia scoparia (L.) Schrad.] covers were 49% and 35% nearest the feedyard and decreased to 9% and 1%, respectively, at &gt; 525 m. Over a similar distance, soil P decreased from 75 to 17 mg kg-1. Dust deposition rate decreased with distance from the feedyard. Manure dust contribution to total dust ranged from negligible to 89%. It was estimated that 20-30 kg N ha-1 year-1 were deposited over 30 years to areas nearest the feedyard. Changes in vegetation and soil P were greatest at &lt; 500 m from the feedyard. Vegetation and soil P were near values expected for shortgrass prairie at &gt; 500 m downwind from the feedyard. The pattern of vegetation, soil fertility, and dust deposition gradients strongly suggested that the feedyard was the primary cause of the observed changes, although a direct causal link could not be established, and other factors, such as grazing, could have contributed to the observed changes.

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.

RESPONSE OF SEVEN CROPS AND TWO SOILS TO APPLICATION OF BEEF CATTLE FEEDYARD EFFLUENT

A greenhouse experiment was conducted to evaluate yield and nutrient uptake following land application of beefcattle feedyard effluent. Effluent from a large commercial feedyard was applied to seven crops planted in 210 pots containingPullman clay loam (PCL) or Amarillo fine sandy loam (AFSL). The crops evaluated were forage sorghum, wheat, corn silage,alfalfa, bromegrass, bermudagrass, and Jose tall wheatgrass. Each crop and soil type received five effluent applicationtreatments representing 0%, 25%, 50%, 100%, and 200% of the annual crop nitrogen requirement and about 0%, 20%, 40%,80%, and 160% of the annual crop phosphorus requirement over the growing period, which ranged from 4 to 12 months. Drymatter yield increased with increasing application rates for all crops except alfalfa in the AFSL, with minimal differencesin dry matter yield for the PCL. For the PCL, all crops except corn silage had foliage crude protein concentrations equal toor greater than published values. For the AFSL, forage sorghum, wheat, and corn silage had foliage crude proteinconcentrations less than typical. In the PCL at the highest application rate, phosphorus uptake rates in the foliage were wheat(16 kg/ha), alfalfa (36 kg/ha), bromegrass (41 kg/ha), Jose tall wheatgrass (37 kg/ha), forage sorghum (47 kg/ha), corn silage(57 kg/ha), and bermudagrass (112 kg/ha). In the AFSL at the highest application rate, phosphorus uptake rates in the foliagewere wheat (10 kg/ha), bromegrass (12 kg/ha), alfalfa (17 kg/ha), forage sorghum (17 kg/ha), Jose tall wheatgrass (20 kg/ha),corn silage (22 kg/ha), and bermudagrass (41 kg/ha). Soil characteristics including electrical conductivity and sodium weregenerally higher after application of effluent for both soil types, although the changes were more pronounced in the AFSLthan the PCL.

Restriction-site-specific PCR as a rapid test to detect enterohemorrhagic Escherichia coli O157:H7 strains in environmental samples.

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is an important food-borne pathogen in industrialized countries. We developed a rapid and simple test for detecting E. coli O157:H7 using a method based on restriction site polymorphisms. Restriction-site-specific PCR (RSS-PCR) involves the amplification of DNA fragments using primers based on specific restriction enzyme recognition sequences, without the use of endonucleases, to generate a set of amplicons that yield "fingerprint" patterns when resolved electrophoretically on an agarose gel. The method was evaluated in a blinded study of E. coli isolates obtained from environmental samples collected at beef cattle feedyards. The 54 isolates were all initially identified by a commonly used polyclonal antibody test as belonging to O157:H7 serotype. They were retested by anti-O157 and anti-H7 monoclonal antibody enzyme-linked immunosorbent assay (ELISA). The RSS-PCR method identified all 28 isolates that were shown to be E. coli O157:H7 by the monoclonal antibody ELISA as belonging to the O157:H7 serotype. Of the remaining 26 ELISA-confirmed non-O157:H7 strains, the method classified 25 strains as non-O157:H7. The specificity of the RSS-PCR results correlated better with the monoclonal antibody ELISA than with the polyclonal antibody latex agglutination tests. The RSS-PCR method may be a useful test to distinguish E. coli O157:H7 from a large number of E. coli isolates from environmental samples.

WATER USE AND CONSERVATION AT TEXAS HIGH PLAINS BEEF CATTLE FEEDYARDS

Water conservation in the Texas High Plains has become increasingly important as groundwater resources are depleted. A water usage study was performed over a two-year period at a 50,000-head beef cattle feedyard. Water usage was correlated to meteorological data from a NOAA weather station. Average daily water usage over the two-year period was 40.9 L/head/d (10.8 gal/head/d). Whenever water trough floats were adjusted for winter conditions, 66% of total usage was for drinking, 2% was used in the feedmill, and 32% was used for overflow to prevent freezing. Whenever water trough floats were adjusted for summer conditions, 89% was used for drinking, 3% was used in the feedmill, and 7% leaked into the overflow collection system. Options identified for conserving water include installing more efficient water troughs, repairing existing troughs, and installing an overflow recycling system. Potential beneficial uses for the overflow water include irrigation of crops, sprinkling pens for dust and temperature control, and use in steam flaking of grain at the feedmill. If all of the overflow water were recycled at this feedyard, then 162 000 m 3 (42.7 million gal) would be conserved per year (22% of total annual use). Construction of a $39,000 filtration-chlorination water treatment system would have a payback period of six years at 8% interest, and result in a net monthly savings of $707 after payback of the capital investment.

Prevalence, antibiotic susceptibility, and genetic diversity of Salmonella, Campylobacter, and Escherichia coli O157:H7 collected at four Kansas beef cattle feedyards over 13 months (1998)

Salmonella, Campylobacter, and Eschericia Escherichia coli O157:H7 isolates will help to coli O157:H7 are important foodborne pathogens, determine 1) their feedyard sources, 2) which but longitudinal studies of their prevalence in beef antibiotics could be effective for cattle therapy, 3) cattle feedyards have not been done. Our longsources that have greatest resistance, 4) whether term study involved 24,556 samples taken from some genetically identical isolates are developing beef cattle feedyards found overall prevalences of resistance over time, and 5) seasonal resistance 4.87% for Salmonella, 20.1% for Campylobacter patterns for each antibiotic tested. Knowing the in hospital pen fecal samples, and 0.20% for E. genetic diversity of organisms such as E. coli coli O157:H7. Yard and pen differences (P<0.05) O157:H7 aids investigators in determining if were detected. All 53 E. coli O157:H7 isolates contamination is due primarily to resident or were resistant to Talmicosin and Erythromycin, transient isolates and could help trace the source two antimicrobials used in food animal medicine. of disease outbreaks. Monitoring the prevalence, Their genetic diversity was high and did not antibiotic susceptibility, and genetic diversity of indicate the presence of resident strains at the foodborne pathogens at cattle feedyards is imporyards studied. Salmonella, Campylobacter, and tant for producers designing production animal E. coli O157:H7 were probably brought into the (preharvest) Hazard Analysis Critical Control yards by shipments of new cattle. Many of these Points (HACCP) programs for pathogen reducorganisms were susceptible to antibiotics comtion. monly used to treat beef cattle.