Lagoon Slurry Research Articles

Diarrheagenic Escherichia coli and Their Antibiotic Resistance Patterns in Dairy Farms and Their Microbial Ecosystems

Ruminants are the largest reservoir for all types of Escherichia coli, including the pathogenic ones, which can potentially be transmitted to humans via the food chain and environment. A longitudinal study was performed to estimate the prevalence and antibiotic-resistant pattern of pathogenic E. coli (pE.coli) strains in dairy farm environments. A total of 846 environmental samples (water, lagoon slurry, bedding, feed, feces, soil, and compost) were collected in summer over two years from five dairy farms in Maryland, USA. An additional 40 soil samples were collected in winter and summer seasons for evaluating microbiome composition. Collected environmental samples were screened for the presence of pE.coli, which was isolated using a selective culture medium, for later confirmation and virotyping using PCR with specific primers. The overall prevalence of pE.coli in dairy farms was 8.93% (71/846), with the most common virotype identified in isolates being ETEC, followed by STEC. The highest pE.coli prevalence were recorded in lagoon slurry (21.57%) while the lowest was in compost heap (2.99%). Among isolates, 95.87% of the virotypes were resistant to 9 classes of antibiotics whereas only 4.12% were sensitive. The highest proportion (68.04%) of resistance was found for quinolones (e.g., ciprofloxacin). The resulting metagenomic analysis at the phylum and genus levels of the grazing land soil suggests that climatic conditions actively influence the abundance of bacteria. Proteobacteria, which contains many Gram-negative foodborne pathogens (including pE.coli), was the most predominant phylum, accounting for 26.70% and 24.93% of soil bacteria in summer and winter, respectively. In addition to relative abundance, there was no significant difference in species diversity between seasons when calculated via Simpson (D) and Shannon (H) index. This study suggests that antibiotic-resistant E. coli virotypes are present in the dairy farm environment, and proper steps are warranted to control its transmission irrespective of seasonality.

Biosolids processing effect on sulfur plant availability

AbstractUnderstanding the S nutritive value of biosolids produced by various processing methods is important for growers who apply biosolids to crop production fields. Our project goals were to determine how processing method and biosolids’ properties influence S availability and S fertilizer value. Fourteen biosolids materials were selected for the trial, including those produced with aerobic digestion (n = 2), anaerobic digestion (n = 5), dual digestion (n = 1), composting (n = 2), lagoon storage (n = 2), sawdust blending (n = 1), and alkaline stabilization (n = 1). Biosolids were air‐dried, ground, and added to a Walla Walla silt loam soil at a rate of 100 mg S kg–1 soil. The treated soils were incubated at 25 ℃ and extracted for SO4–S on Days 1, 13, 29, 44, and 83. Mean plant available S was greatest for the alkaline stabilized biosolids (52%), followed by anaerobically digested biosolids (40%), sawdust blended biosolids (37%), lagoon slurry (36%), dual digestion biosolids (31%), aerobically digested biosolids (15%), and composted biosolids (4%). Biosolids pH, organic C/total S, total Ca, total S, and SO4–S concentrations were well correlated to S release rate, plant available S, or both. Sulfur mineralization of organic S compounds is known to be influenced by organic C/total S, whereas Ca and pH effects may be related to gypsum (CaSO4) dissolution and oxidation of hydrogen sulfide compounds. The correlations discussed here may need to be further investigated and verified on additional soil types and under field conditions prior to grower adoption.

An object-oriented Bayesian network approach for establishing swine manure-borne natural estrogenic compounds budget

A facility-wide estrogen budget model was developed to assess the excretion of natural estrogens by swine in a commercial swine farrowing concentrated animal feeding operations (CAFO) in North Carolina, using an object-oriented Bayesian network (OOBN) approach. The OOBN model is the combination of twelve objects of Bayesian network models, which characterize the estrogen budget flows based on the sow reproductive cycle (i.e., pre-estrus, estrus, and lactation) for the three natural estrogen types [estrone (E1), 17β-estradiol (E2), and estriol (E3)] within each barn. This OOBN model provides a mechanism to quantify the levels of the natural estrogens and their probabilistic distributions with regard to estrogen type, waste sources such as urine, feces, and recycling lagoon slurry, and animal reproductive status. Moreover, the OOBN model allows us to assess the overall contribution of natural estrogen compounds from each operational unit of the CAFO, while accounting for the uncertainties. Results from the OOBN model indicate a rank order of lactating sows > gestating sows > breeding sows in terms of contribution of estrogen loads to the total natural estrogen budget. As to estrogen type, E1 was found as the major estrogen metabolite with the summed concentrations of urine, feces, and flushing slurry wastes exceeding 3000 ng/l > 90% of the time. As to waste sources, the flushing slurry waste was found to be a major contributor of the estrogen budget compared with urine and feces wastes from barn animals.

Effect of Manure Application Rate and Rainfall Timing on the Leaching of Antibiotic-Resistant Bacteria and Their Associated Genes

In this study, we investigate the effect of application rate and timing of liquid swine slurry on leaching of antibiotic-resistant bacteria (ARB) and their antibiotic resistance genes (ARGs) through soil columns. Swine slurry was added to laboratory soil columns at rates of 5000 or 30,000 gal ac−1. For both application rates, rainfall was applied at either 1, 7, or 21 days after slurry application. Column effluent and the top centimeter of soil in the columns were sampled post-rainfall for cultivable bacteria and quantitative PCR was used to quantify tetracycline, methicillin, β-lactam, and erythromycin resistance genetic determinants. We also conducted similar experiments using swine lagoon slurry spiked with antibiotic-resistant E. coli and Salmonella. We found that the concentration of ARB and ARG recovered in the column effluent following application of the swine lagoon slurry generally decreased with increasing lag time between slurry application and simulated rainfall, though most of these decreases were not statistically significant. Moreover, no statistically significant differences in CFU or GU concentration in the column leachate were observed between the low and high slurry application rates. In the experiments using swine slurry spiked with E. coli and Salmonella, concentrations of both microorganisms eluted from fine sand columns were affected by both slurry application rate and lag time; recovery of ARGs, however, was mostly unaffected, but some differences were observed. In columns packed with loamy sand, no recovery was detected in the column effluent for either organism and recovery of ARG was unaffected by manure application rate or rainfall lag time.

Predicting characteristics of rainfall driven estrogen runoff and transport from swine AFO spray fields

Animal feeding operations (AFOs) have been implicated as potentially major sources of estrogenic contaminants into the aquatic environment due to the relatively minimal treatment of waste and potential mobilization and transport of waste components from spray fields. In this study a Bayesian network (BN) model was developed to inform management decisions and better predict the transport and fate of natural steroidal estrogens from these sites. The developed BN model integrates processes of surface runoff and sediment loss with the modified universal soil loss equation (MUSLE) and the soil conservation service curve number (SCS-CN) runoff model. What-if scenario simulations of lagoon slurry wastes to the spray fields were conducted for the most abundant natural estrogen estrone (E1) observed in the system. It was found that E1 attenuated significantly after 2months following waste slurry application in both spring and summer seasons, with the overall attenuation rate predicted to be higher in the summer compared to the spring. Using simulations of rainfall events in conjunction with waste slurry application rates, it was predicted that the magnitude of E1 runoff loss is significantly higher in the spring as compared to the summer months, primarily due to spray field crop management plans. Our what-if scenario analyses suggest that planting Bermuda grass in the spray fields is likely to reduce runoff losses of natural estrogens near the water bodies and ecosystems, as compared to planting of soybeans.

Transport of steroid hormones, phytoestrogens, and estrogenic activity across a swine lagoon/sprayfield system.

The inflow, transformation, and attenuation of natural steroid hormones and phytoestrogens and estrogenic activity were assessed across the lagoon/sprayfield system of a prototypical commercial swine sow operation. Free and conjugated steroid hormones (estrogens, androgens, and progesterone) were detected in urine and feces of sows across reproductive stages, with progesterone being the most abundant steroid hormone. Excreta also contained phytoestrogens indicative of a soy-based diet, particularly, daidzein, genistein, and equol. During storage in barn pits and the anaerobic lagoon, conjugated hormones dissipated, and androgens and progesterone were attenuated. Estrone and equol persisted along the waste disposal route. Following application of lagoon slurry to agricultural soils, all analytes exhibited attenuation within 2 days. However, analytes including estrone, androstenedione, progesterone, and equol remained detectable in soil at 2 months postapplication. Estrogenic activity in the yeast estrogen screen and T47D-KBluc in vitro bioassays generally tracked well with analyte concentrations. Estrone was found to be the greatest contributor to estrogenic activity across all sample types. This investigation encompasses the most comprehensive suite of natural hormone and phytoestrogen analytes examined to date across a livestock lagoon/sprayfield and provides global insight into the fate of these analytes in this widely used waste management system.

A Bayesian network model for assessing natural estrogen fate and transport in a swine waste lagoon.

Commercial swine waste lagoons are regarded as a major reservoir of natural estrogens, which have the potential to produce adverse physiological effects on exposed aquatic organisms and wildlife. However, there remains limited understanding of the complex mechanisms of physical, chemical, and biological processes that govern the fate and transport of natural estrogens within an anaerobic swine lagoon. To improve lagoon management and ultimately help control the offsite transport of these compounds from swine operations, a probabilistic Bayesian network model was developed to assess natural estrogen fate and budget and then compared against data collected from a commercial swine field site. In general, the model was able to describe the estrogen fate and budget in both the slurry and sludge stores within the swine lagoon. Sensitivity analysis within the model demonstrated that the estrogen input loading from the associated barn facility was the most important factor in controlling estrogen concentrations within the lagoon slurry storage, whereas the settling rate was the most significant factor in the lagoon sludge storage. The degradation reactions were shown to be minor in both stores based on prediction of average total estrogen concentrations. Management scenario evaluations demonstrated that the best possible management options to reduce estrogen levels in the lagoon are either to adjust the estrogen input loading from swine barn facilities or to effectively enhance estrogen bonding with suspended solids through the use of organic polymers or inorganic coagulants.

Comprehensive assessment of hormones, phytoestrogens, and estrogenic activity in an anaerobic swine waste lagoon.

In this study, the distribution of steroid hormones, phytoestrogens, and estrogenic activity was thoroughly characterized within the anaerobic waste lagoon of a typical commercial swine sow operation. Three independent rounds of sampling were conducted in June 2009, April 2010, and February 2011. Thirty-seven analytes in lagoon slurry and sludge were assessed using LC/MS-MS, and yeast estrogen screen was used to determine estrogenic activity. Of the hormone analytes, steroidal estrogens were more abundant than androgens or progesterone, with estrone being the predominant estrogen species. Conjugated hormones were detected only at low levels. The isoflavone metabolite equol was by far the predominant phytoestrogen species, with daidzein, genistein, formononetin, and coumestrol present at lower levels. Phytoestrogens were often more abundant than steroidal estrogens, but contributed minimally toward total estrogenic activity. Analytes were significantly elevated in the solid phases of the lagoon; although low observed log KOC values suggest enhanced solubility in the aqueous phase, perhaps due to dissolved or colloidal organic carbon. The association with the solid phase, as well as recalcitrance of analytes to anaerobic degradation, results in a markedly elevated load of analytes and estrogenic activity within lagoon sludge. Overall, findings emphasize the importance of adsorption and transformation processes in governing the fate of these compounds in lagoon waste, which is ultimately used for broadcast application as a fertilizer.

Effect of redox potential and pH status on degradation and adsorption behavior of tylosin in dairy lagoon sediment suspension

Veterinary antibiotics are the most heavily used pharmaceuticals in intensive animal farming operation. Their presence in the environment through application of manure and lagoon water as fertilizer in agricultural fields has generated a growing concern in recent years due to potential threat to the ecosystem and the risk they pose to human and animal health. Among the antibiotics, tylosin, a macrolide class of antibiotics, has been widely used for disease prevention and growth promotion in swine, cattle/dairy, and poultry production. To understand degradation and sorption behavior of tylosin A, a laboratory microcosm incubation study was conducted on dairy lagoon sediments suspension under different pH (5.5, 7.0, 8.5) and redox potentials (Eh at −100mV, 0mV, +250mV, +350mV). Sorption and degradation of tylosin was strongly influenced by sediment pH and redox conditions. Under acidic (pH 5.5) and reduced (Eh −100mV) condition, tylosin persisted in the solution phase of dairy lagoon sediment suspension much longer with resident time of 77d. Under oxidized (Eh +350mV) condition, microbial degradation was much greater causing 68–75% of tylosin loss from the solution at pH 5.5 and 32–75% at pH 7.0 during the 20d incubation. At pH 8.5, abiotic transformation of tylosin A into unknown degradates rather than sediment adsorption and microbial degradation was the major mechanism controlling tylosin disappearance from the solution regardless of the status of redox potentials. Overall, the results suggested that under reduced condition with low pH, tylosin will be persisted in the lagoon effluents and residue of tylosin may enter agricultural fields through the application of lagoon slurry as fertilizer.

Characterization of skatole-producing microbial populations in enriched swine lagoon slurry

Skatole is one of the most malodorous compounds produced from the anaerobic degradation of animal waste. Little is known about the biochemistry of skatole production, the phylogeny of skatole-producing microorganisms or the conditions that favor their growth. These deficiencies hamper attempts to reduce skatole production. Our goals were to enrich for skatole producers in swine lagoon slurry (SLS) and evaluate the resulting microbial community structure using denaturing gradient gel electrophoresis (DGGE) and 16S rRNA gene sequence analysis. Skatole producers were enriched by incubating dilutions of SLS with 100 muM indole-3-acetic acid (IAA). GC-MS was used to measure skatole production in the slurries after 0, 7 and 17 days' incubation. Based on most probable number analysis, skatole producers increased 100-fold in SLS samples supplemented with IAA. Based on DGGE fingerprint patterns from day 0, 7 and 17 treatments with high, mid or low levels of skatole production, changes in the SLS population occurred as skatole production increased. Changes in the bacterial community fingerprints were associated with an increase in the low-GC gram-positive and Bacteroides groups. Results from this study provides valuable new information concerning the organisms responsible for production of this odorant, a necessary first step towards controlling skatole production.

Cover crop effects on the fate of N following soil application of swine manure

Cereal grain cover crops increase surface cover, anchor corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) residues, increase infiltration, reduce both rill and interrill erosion, scavenge excess nutrients from the soil, and are easily obtained and inexpensive com- pared to other cover crop options. The use of cereal grain cover crops in fields where manure application occurs should increase nitrogen (N) recovery and cycling for use in subsequent crops. The objectives of this study were to determine if a rye (Secale cereale L.) cover crop increases N retention after soil application of swine lagoon slurry. Experiments were conducted in a con- trolled environment chamber using plastic buck- ets as the experimental units. Three manure-N loading rates (no manure, low, high) were applied to soils with and without a rye cover crop. A partial N balance was determined from measure- ments of NO3 leaching, N2 Oa nd NH 3 emissions, cover crop N uptake, and NO3 +N H 4 remaining in the soil. Cumulative nitrate load in the drain- age water was less than 0.31 g m -2 NO3-N for rye treatments regardless of the manure rate, how- ever in the fallow treatments, at the high manure rate NO3 leaching losses were 6.28 and 3.77 g m -2 NO3-N, for experiments 1 and 2, respectively. Rye N uptake ranged from 2.95 g N m -2 to 10.7 g N m -2 , and was related to manure rate. Rye had lower cumulative N2O emission than the no rye treatment for the high manure treatment. Ammonia emissions were low for all treatments during both experiments, which was probably related to the rapid manure incorporation after application. Rye can increase N retention, reduce cumulative N2O emissions, and reduce cumula- tive N load in drainage water when manure is applied to soils. Nitrogen balance calculations in the cover crop treatments accounted for less than the equivalent of 50% of the added manure N. We speculate that the living rye plants may have increased immobilization of N in the organic N pools.

Long-term persistence of multi–drug-resistant Salmonella enterica serovar Newport in two dairy herds

To evaluate the association between maintaining joint hospital and maternity pens and persistence of multi-drug-resistant (MDR) Salmonella enterica serovar Newport on 2 dairy farms. Observational study. Feces and environmental samples from 2 dairy herds. Herds were monitored for fecal shedding of S enterica Newport after outbreaks of clinical disease. Fecal and environmental samples were collected approximately monthly from pens housing sick cows and calving cows and from pens containing lactating cows. Cattle shedding the organism were tested serially on subsequent visits to determine carrier status. One farm was resampled after initiation of interventional procedures, including separation of hospital and maternity pens. Isolates were characterized via serotyping, determination of antimicrobial resistance phenotype, detection of the CMY-2 gene, and DNA fingerprinting. The prevalence (32.4% and 33.3% on farms A and B, respectively) of isolating Salmonella from samples from joint hospital-maternity pens was significantly higher than the prevalence in samples from pens housing preparturient cows (0.8%, both farms) and postparturient cows on Farm B (8.8%). Multi-drug-resistant Salmonella Newport was isolated in high numbers from bedding material, feed refusals, lagoon slurry, and milk filters. One cow excreted the organism for 190 days. Interventional procedures yielded significant reductions in the prevalences of isolating the organism from fecal and environmental samples. Most isolates were of the C2 serogroup and were resistant to third-generation cephalosporins. Management practices may be effective at reducing the persistence of MDR Salmonella spp in dairy herds, thus mitigating animal and public health risk.

IMPACT OF ANAEROBIC LAGOON MANAGEMENT ON SLUDGE ACCUMULATION AND NUTRIENT CONTENT FOR DAIRIES

The contents of twelve primary dairy lagoon cells under different management practices in three central Texascounties were evaluated for sludge accumulation and physicochemical characteristics. Composite samples were comprisedof the wastewater column from the top of the lagoon to the top of the dense sludge layer. The composite samples were thoughtto represent a slurry mix typical of agitated lagoon material intended for land disposal. Analyses included pH, total solids(TS), volatile solids (VS), total Kjeldahl nitrogen (TKN), total ammonium-nitrogen (NH4 -N), phosphorus (P), potassium (K),calcium (Ca), magnesium (Mg), sodium (Na), zinc (Zn), copper (Cu), manganese (Mn), and electrical conductivity (EC).<br><br>Statistically, lagoon management practices and treatment effectiveness in terms of reduced sludge accumulation andnutrient content were not strongly linked. However, some practices appear to influence the physicochemical properties of theslurry mix, including use of fresh flush water, increasing the number of treatment cells, and separation of dry lot runoff. TotalKjeldahl nitrogen, P, and K were linearly correlated to TS, indicating higher nutrient concentrations in the anaerobic lagoonsludge. The resultant elevated nutrient levels in the slurry mix, compared to supernatant values, will require greater land areasto meet P-based regulations. Land applying a lagoon slurry mix will require approximately two and a half times as much landarea compared to N-based application rates. Consideration of best management practices (BMPs) may be advised to alleviatelagoon clean-out and sludge disposal challenges.