Michael R. McLaughlin

Rainfall simulation in greenhouse microcosms to assess bacterial-associated runoff from land-applied poultry litter.

Runoff water following a rain event is one possible source of environmental contamination after a manure application. This greenhouse study used a rainfall simulator to determine bacterial-associated runoff from troughs of common bermudagrass [Cynodon dactylon (L.) Pers.] that were treated with P-based, N-based, and N plus lime rates of poultry (Gallus gallus) litter, recommended inorganic fertilizer, and control. Total heterotrophic plate count (HPC) bacteria, total and thermotolerant coliforms, enterococci, staphylococci, Clostridium perfringens, Salmonella, and Campylobacter, as well as antibiotic resistance profiles for the staphylococci and enterococci isolates were all monitored in runoff waters. Analysis following five rainfall events indicated that staphylococci, enterococci, and clostridia levels were related to manure application rate. Runoff release of staphylococci, enterococci, and C. perfringens were approximately 3 to 6 log10 greater in litter vs. control treatment. In addition, traditional indicators such as thermotolerant and total coliforms performed poorly as fecal indicators. Some isolated enterococci demonstrated increased antibiotic resistance to polymixin b and/or select aminoglyocosides, while many staphylococci were susceptible to most antimicrobials tested. Results indicated poultry litter application can lead to microbial runoff following simulated rain events. Future studies should focus on the use of staphylococci, enterococci, and C. perfringens as indicators.

Land application of manure and Class B biosolids: an occupational and public quantitative microbial risk assessment.

Land application is a practical use of municipal Class B biosolids and manure that also promotes soil fertility and productivity. To date, no study exists comparing biosolids to manure microbial risks. This study used quantitative microbial risk assessment to estimate pathogen risks from occupational and public exposures during scenarios involving fomite, soil, crop, and aerosol exposures. Greatest one-time risks were from direct consumption of contaminated soil or exposure to fomites, with one-time risks greater than 10. Recent contamination and high exposures doses increased most risks. and enteric viruses provided the greatest single risks for most scenarios, particularly in the short term. All pathogen risks were decreased with time, 1 d to14 mo between land application and exposure; decreases in risk were typically over six orders of magnitude beyond 30 d. Nearly all risks were reduced to below 10 when using a 4-mo harvest delay for crop consumption. Occupational, more direct risks were greater than indirect public risks, which often occur after time and dilution have reduced pathogen loads to tolerable levels. Comparison of risks by pathogen group confirmed greater bacterial risks from manure, whereas viral risks were exclusive to biosolids. A direct comparison of the two residual types showed that biosolids use had greater risk because of the high infectivity of viruses, whereas the presence of environmentally recalcitrant pathogens such as and maintained manure risk. Direct comparisons of shared pathogens resulted in greater manure risks. Overall, it appears that in the short term, risks were high for both types of residuals, but given treatment, attenuation, and dilution, risks can be reduced to near-insignificant levels. That being said, limited data sets, dose exposures, site-specific inactivation rates, pathogen spikes, environmental change, regrowth, and wildlife will increase risk and uncertainty and remain areas poorly understood.

EFFECT OF LONG-TERM SWINE EFFLUENT APPLICATION ON SELECTED SOIL PROPERTIES

Improving swine effluent management practices requires understanding of the fate of nutrients derived from swine effluent in soil quality. This study was conducted to evaluate the effects of long-term swine lagoon effluent application on nutrient distribution in an alkaline Okolona silty clay, an acidic Vaiden silty clay, and a Brooksville silty clay loam. Swine effluent has been applied using a center-pivot irrigation system at a total rate ranging from 10 to 15 cm ha−1 of effluent per year since 1990. In October 2005, soil samples were taken from the irrigated and nonirrigated sites at the following depths: 0 to 5, 5 to 15, 15 to 30, 30 to 60, and 60 to 90 cm. Soils were air-dried, ground to pass 2-mm sieve, and analyzed for selected chemical properties. Sorption isotherms were also performed on the soil samples to determine P sorption capacity and strength. Long-term application of swine effluent resulted in a decrease in soil pH and an increase in soil electrical conductivity in all three soils. Total soil C and microbial biomass C increased in irrigated sites for all soils. Soil ammonium, nitrate, acid-extractable P, water-soluble P, and Zn concentrations were elevated at the 0- to 5-cm and 5- to 15-cm depths, and their values were extremely lower in the alkaline Okolona soil than in the Brooksville and Vaiden soils. No clear effect was observed for P sorption strength and capacity. Low N and P accumulation in alkaline Okolona soil may prolong the capacity of this soil in receiving swine effluent particularly if threshold water-soluble P and soil test P levels are used as part of swine effluent management program.

Characterization of Selected Nutrients and Bacteria from Anaerobic Swine Manure Lagoons on Sow, Nursery, and Finisher Farms in the Mid-South USA

Swine (Sus scrofa domestica) production in the Mid-South USA comprises sow, nursery, and finisher farms. A 2007 packing plant closure started a regional shift from finisher to sow and nursery farms. Changes in manure stored in lagoons and land-applied as fertilizer were expected but were unknown because nutrient and bacterial levels had not been characterized by farm type. The objectives of this study were to quantify selected nutrients and bacteria, compare levels by farm types, and project impacts of production shifts. Nutrients and bacteria were characterized in 17 sow, 10 nursery, and 10 finisher farm lagoons. Total and thermotolerant coliforms, Escherichia coli (Migula) Castellani and Chalmers, Enterococcus spp., Clostridium perfringens (Veillon and Zuber) Hauduroy et al., Campylobacter spp., Listeria spp., and Salmonella spp. were evaluated. Highest levels were from total coliforms (1.4- 5.7x10(5) cfu 100 mL(-1)), which occurred with E. coli, Campylobacter spp., C. perfringens, and Enterococcus spp., in every lagoon and virtually every sample. Lowest levels were from Listeria spp. and Salmonella spp. (<or=1.3x10(2) most probable number [MPN] 100 mL(-1)), detected in 81 and 89% of lagoons and 68 and 64% of samples, respectively. Sow farm levels were higher for all except Listeria spp. and Salmonella spp., which were lower (1.4x10(1) and 2.8x10(1) MPN 100 mL(-1), respectively) and only slightly below their respective levels from nursery farms (1.1x10(2) and 3.4x10(1) MPN 100 mL(-1)). Shifting from finisher to nursery farm would not affect bacterial levels, but shifting to sows would. Either shift would reduce NPK and N:P and suggest modification of nutrient management plans.

Temporal flux and spatial dynamics of nutrients, fecal indicators, and zoonotic pathogens in anaerobic swine manure lagoon water.

Confined animal feeding operations (CAFOs) often use anaerobic lagoons for manure treatment. In the USA, swine CAFO lagoon water is used for crop irrigation that is regulated by farm-specific nutrient management plans (NMPs). Implementation of stricter US environmental regulations in 2013 will set soil P limits; impacting land applications of manure and requiring revision of NMPs. Precise knowledge of lagoon water quality is needed for formulating NMPs, for understanding losses of N and C in ammonia and greenhouse gas emissions, and for understanding risks of environmental contamination by fecal bacteria, including zoonotic pathogens. In this study we determined year-round levels of nutrients and bacteria from swine CAFO lagoon water. Statistical analysis of data for pH, electrical conductivity (EC), inorganic and organic C, total N, water-soluble and total minerals (Ca, Cu, Fe, K, Mg, Mn, P, and Zn) and bacteria (Escherichia coli, enterococci, Clostridium perfringens, Campylobacter spp., Listeria spp., Salmonella spp., and staphylococci) showed that all differed significantly by dates of collection. During the irrigation season, levels of total N decreased by half and the N:P ratio changed from 9.7 to 2.8. Some seasonal differences were correlated with temperature. Total N and inorganic C increased below 19 °C, and decreased above 19 °C, consistent with summer increases in ammonia and greenhouse gas emissions. Water-soluble Cu, Fe, and Zn increased with higher summer temperatures while enterococci and zoonotic pathogens (Campylobacter, Listeria, and Salmonella) decreased. Although their populations changed seasonally, the zoonotic pathogens were present year-round. Increasing levels of E. coli were statistically correlated with increasing pH. Differences between depths were also found. Organic C, total nutrients (C, Ca, Cu, Fe, Mg, Mn, N, P, and Zn) and C. perfringens were higher in deeper samples, indicating stratification of these parameters. No statistical interactions were found between collection dates and depths.

Antibiotic resistant bacterial profiles of anaerobic swine lagoon effluent.

Although land application of swine (Sus scrofa) manure lagoon effluent is a common and effective method of disposal, the presence of antibiotic-resistant bacteria, both pathogenic and commensal can complicate already understood issues associated with its safe disposal. The aim of this study was to assess antibiotic resistance in swine lagoon bacteria from sow, nursery, and finisher farms in the southeastern United States. Effluents from 37 lagoons were assayed for the presence of Escherichia coli, Campylobacter, Listeria, and Salmonella. Antibiotic resistance profiles were determined by the Kirby-Bauer swab method for 12 antibiotics comprising eight classes. Statistical analyses indicated that farm type influenced the amount and type of resistance, with nurseries and sow farms ranking as most influential, perhaps due to use of more antibiotic treatments. Finisher farms tended to have the least amount of antibiotic class resistance, signaling an overall healthier market pig, and less therapeutic or prophylactic antibiotic use. Many bacterial isolates were resistant to penicillin, cephalosporin, and tetracycline class antibiotics, while nearly all were susceptible to quinolone antibiotics. It appeared that swine farm type had a significant association with the amount of resistance associated with bacterial genera sampled from the lagoons; nurseries contributed the largest amount of bacterial resistance.

The effect of poultry manure application rate and AlCl3 treatment on bacterial fecal indicators in runoff

Increasing costs associated with inorganic fertilizer have led to widespread use of broiler litter. Proper land application, typically limiting nutrient loss, is essential to protect surface water. This study was designed to evaluate litter-borne microbial runoff (heterotrophic plate count bacteria, staphylococci, Escherichia coli, enterococci, and Clostridium perfringens) while applying typical nutrient-control methods. Field studies were conducted in which plots with high and low litter rates, inorganic fertilizer, AlCl(3)-treated litter, and controls were rained on five times using a rain generator. Overall, microbial runoff from poultry litter applied plots was consistently greater (2-5 log(10) plot(-1)) than controls. No appreciable effect on microbial runoff was noted from variable litter application rate or AlCl(3) treatments, though rain event, not time, significantly affected runoff load. C. perfringens and staphylococci runoff were consistently associated with poultry litter application, during early rain events, while other indicators were unreliable. Large microbial runoff pulses were observed, ranging from 10(2) to 10(10) CFU plot(-1); however, only a small fraction of litter-borne microbes were recoverable in runoff. This study indicated that microbial runoff from litter-applied plots can be substantial, and that methods intended to reduce nutrient losses do not necessarily reduce microbial runoff.

Cultivation and qPCR Detection of Pathogenic and Antibiotic-Resistant Bacterial Establishment in Naive Broiler Houses.

Conventional commercial broiler production involves the rearing of more than 20,000 broilers in a single confined space for approximately 6.5 wk. This environment is known for harboring pathogens and antibiotic-resistant bacteria, but studies have focused on previously established houses with mature litter microbial populations. In the current study, a set of three naive houses were followed from inception through 11 broiler flocks and monitored for ambient climatic conditions, bacterial pathogens, and antibiotic resistance. Within the first 3 wk of the first flock cycle, 100% of litter samples were positive for and , whereas was cultivation negative but PCR positive. Antibiotic resistance genes were ubiquitously distributed throughout the litter within the first flock, approaching 10 to 10 genomic units g. Preflock litter levels were approximately 10 CFU g for heterotrophic plate count bacteria, whereas midflock levels were >10 colony forming units (CFU) g; other indicators demonstrated similar increases. The influence of intrahouse sample location was minor. In all likelihood, given that preflock levels were negative for pathogens and antibiotic resistance genes and 4 to 5 Log lower than flock levels for indicators, incoming birds most likely provided the colonizing microbiome, although other sources were not ruled out. Most bacterial groups experienced a cyclical pattern of litter contamination seen in other studies, whereas microbial stabilization required approximately four flocks. This study represents a first-of-its-kind view into the time required for bacterial pathogens and antibiotic resistance to colonize and establish in naive broiler houses.

Effects of bedding materials in applied poultry litter and immobilizing agents on runoff water, soil properties, and bermudagrass growth.

Poultry producers in the United States have begun using different types of bedding materials in production houses. Release into the environment of nutrients from applied poultry litter (PL) made with different bedding materials has not been investigated, and little information is available on nutrient concentrations in soils that receive broiler litter made with such materials. In this greenhouse study, two bedding materials (rice hulls and pine chips) in PL and two nutrient-immobilizing agents (gypsum and biochar) were applied to bermudagrass, and chemical and microbial contents of runoff water, soil properties, and plant growth were evaluated. Treatments with rice hull bedding material in PL had less runoff nutrient and greater soil soluble N and P compared with pine chip bedding. Gypsum and biochar both significantly reduced C, N, P, Cu, and Zn losses from the first runoff event, which were reduced by 26, 30, 37, 38, and 38% and by 25, 24, 30, 29, and 35%, respectively, but only gypsum obviously reduced these nutrients from later events. Potassium, Ca, Mg, and Mn increased by 2, 36, 11, and 9 times, respectively, and soluble P, Cu, and Fe significantly decreased by 68, 72, and 98%, respectively, in soil amended with gypsum. Rice hull PL in combination with gypsum significantly increased the growth of bermudagrass. Our results indicate that rice hull PL posed less risk for nutrient loss than pine chip PL when applied to fields and that gypsum was better than biochar for reducing runoff C, N, P, and Cu.

Runoff quality from no-till cotton fertilized with broiler litter in subsurface bands.

Surface broadcast of broiler litter to no-till row crops exposes the litter and its nutrients to risks of loss in runoff water and volatilization and may limit the potential benefit of litter to the crops. Subsurface banding of litter could alleviate these risks. A field study was conducted in 2008 and 2009 on an upland Falkner silt loam soil to determine the effect of broiler litter placement on runoff nutrient losses from no-till cotton ( L.). Treatments included surface broadcast broiler litter applied manually, subsurface-banded litter applied by tractor-drawn equipment, and no broiler litter, all in combination with or without winter wheat ( L.) cover crop residue. Broiler litter rate was 5.6 Mg ha. The experimental design was a randomized complete block with a split-plot arrangement of treatments replicated three times. In 2008, simulated rainfall was used to generate runoff 27 d after litter application. Subsurface-banded litter reduced runoff total C, N, P, NH, NO, Cu, Zn and water-soluble P (WP) concentrations by 72, 64, 51, 49, 70, 36, 65, and 77%, respectively, compared with surface broadcast. The reductions were greater in 2009 where runoff occurred 1 d after litter application. Bacterial runoff was decreased by one log with subsurface-banded litter compared to surface broadcast. Except for C, NH, N, and WP, the presence of winter cover crop residue did not affect the load or runoff nutrient concentrations in either year. The results indicate that subsurface banding litter to no-till cotton substantially reduces nutrient and bacterial losses in runoff compared with surface broadcasting.