The effect of benzoic acid with or without a direct-fed microbial on the nutrient metabolism and gas emissions of growing pigs

Twenty-four gilts (PIC 337 × 1050, PIC Genus, Hendersonville, TN) with an initial body weight (BW) of 33.09 ± 1.33 kg were used to investigate the effects of benzoic acid (BA) and a Bacillus-based direct-fed microbial (DFM) on the nutrient metabolism and manure gas emissions of growing pigs. Pigs were blocked by BW, placed into metabolism stalls, and randomly assigned to one of four dietary treatments: basal control (PC), low nitrogen (NC), PC plus 0.3% BA (PC+BA; VevoVitall, DSM Nutritional Products), and PC plus 0.3% BA and 0.025% DFM (PC+BA+DFM; PureGro, DSM Nutritional Products). Pigs were fed a common diet from day 0 to 14, and the experimental diets were fed in two phases (day 14 to 28 and day 28 to 53). The experiment consisted of four collection periods, with each period subdivided into two subperiods to collect samples for gas emissions and nutrient balance. Firstly, manure samples were collected for 72 h. Twice daily, urine and feces were weighed, and urine pH was measured. After each period, manure was subsampled and taken to the lab to measure gas emissions. Secondly, urine and feces were quantitatively collected for 96 h to allow for measurement of nutrient digestibility (ATTD) and retention. Data were analyzed as repeated measures in SAS 9.4 (SAS Inst., Cary, NC) with fixed effects of treatment, collection period, and block. Pig was the experimental unit, and results were considered significant at P ≤ 0.05 and a tendency at 0.05 < P ≤ 0.10. Pigs fed PC+BA had the greatest ADG compared to pigs fed NC (P = 0.016), with intermediate ADG for pigs fed PC or PC+BA+DFM (P ≥ 0.148). The ATTD of dry matter, gross energy, P, and N did not differ between treatments (P ≥ 0.093). However, the ATTD of Ca was reduced in pigs fed PC+BA+DFM compared to pigs fed PC+BA (P = 0.012). Pigs fed PC+BA or NC excreted less urinary N compared to PC and PC+BA+DFM (P ≤ 0.034), which contributed to greater nitrogen retention in PC+BA compared to PC (P = 0.016). Furthermore, decreased manure pH from pigs fed PC+BA or NC resulted in lower ammonia (NH₃) emissions compared to pigs fed PC+BA+DFM or PC. There was no effect of dietary treatment on manure hydrogen sulfide, methane, or carbon dioxide emissions. In conclusion, supplementing 0.3% BA improved N retention and reduced manure pH and NH₃ emissions, similar to feeding pigs low N, but improved the ADG of pigs when compared to feeding a low N diet.

Swine diets: Impact of carbohydrate sources on manure characteristics and gas emissions

Swine growers seeking to lower costs and environmental impact have turned to alternative carbohydrate feed sources. A feeding trial was conducted to determine the effect carbohydrate sources have on manure composition and gas emissions. A total of 48 gilts averaging 138 kg BW were fed diets consisting of (a) low fiber (LF) grain, or (b) high fiber (HF) aro-industrial co-product (AICP). The LF diets included corn and soybean meal (CSBM) and barley soybean meal (BSBM). The HF AICP diets were CSBM based and supplemented with one of the following materials: beet pulp; corn distillers dried grains with solubles; soybean hulls; or wheat bran. Diets were fed for 42 d with an average daily feed intake of 2.71 kg d-1. Feces and urine were collected twice daily and added to manure storage containers in which manure slurries were monitored for gas emissions and chemical properties. Manures of animals fed HF diets had significantly (P < 0.05) more excretion of solids, C, N, and organic N, but less total S compared to pigs fed the LF diets. Animals feed HF diets had significantly (P < 0.05) higher levels of ammonia, sulfide, volatile fatty acids, and phenols in manure compared to pigs fed the LF diets. Manure of animals fed HF diets had 30% (P < 0.05) lower NH3 and 17% lower hydrogen sulfide emissions; however, fiber had no impact on odor emissions. Based on the partitioning of nutrients, animals fed HF fiber diets had increased manure retention for C and N but decreased levels of N gas emissions and manure S. There were little differences in manure and gas emissions for animals fed LF diets, but the source of HF AICP diets had a significant impact on manure composition and gas emissions.

Swine diets impact manure characteristics and gas emissions: Part II protein source

Soybean meal is the dominate protein source for swine diets in the world driven largely by economics, nutritive value, and availability; but conditions can change requiring growers to consider more economical and available protein alternatives. A feeding trial was conducted to determine the impact dietary protein source material on manure slurry chemical properties and manure gas emissions. A total of 32 gilts averaging 130 kg BW were fed either a control diet formulated with soybean meal (SB) or an alternative protein source that included corn gluten meal (CG); canola meal (CM); or poultry meal (PM), with all diets containing 176 g protein kg^-1. Diets were fed for 45 d with an average daily feed intake of 2.68 kg/d. Feces and urine were collected twice daily after each feeding and added to animal-specific manure storage containers. At the end of the study, manure slurries were monitored for gas emissions and chemical properties. Dietary protein source had a significant effect (P < 0.05) on manure pH, total solids, total C, protein N, and total S. Pigs fed the diets containing CM had significantly higher levels of sulfide, butanoic acid, and branch chain fatty acids compared to pigs fed SB diets (P < 0.05). Pigs fed CM diets had significantly lower emissions of NH₃ compared to pigs fed SB diets (P < 0.05). There were no significant differences in C or S emissions or in odorant emission as affected by source of dietary protein. Hydrogen sulfide was the most dominate odorants for all dietary treatments.

Swine diets impact manure characteristics and gas emissions: Part I protein level

Crude protein (CP) is a key nutrient in swine diets supplying essential amino acids, N, and S to animals for growth are fed in excess to maximize growth. Swine diets reduced in CP and supplemented with crystalline amino acids have been shown effective at maintaining animal growth while increasing overall CP use efficiency. A feeding trial study was conducted to determine the effects of reduced dietary CP levels on manure slurry chemical properties and gas emissions. A total of 24 gilts averaging 111 kg BW were fed corn and soybean meal diets formulated with 8.7, 14.8, and 17.6% CP using crystalline amino acid supplementation in the 8.7 and 14.8% CP diets, but only intact protein, soybean meal, in the diet containing 17.6% CP. Diets were fed for 45 d with an average daily feed intake (ADFI) of 2.70 kg across all diets. Animals were fed twice daily with both feces and urine collected during each feeding and added to animal-specific manure storage containers. At the end of the study, manure slurries were monitored for gas emissions and chemical properties. Increasing dietary CP levels increased manure pH, total solids, total N, and total S, including increased levels of ammonia (NH₃), volatile fatty acids, and phenolic compounds. Pigs fed lower CP diets had lower emissions of NH₃, branched chain fatty acids (BCFA), and phenol compounds which translated into lower emissions in total odor. Emissions of NH₃ and odor were reduced by 8.9% and 4.2%, respectively, for each unit percent decline in dietary CP. Hydrogen sulfide was the dominate odorant associated with manure odor emissions. Based on nutrient mass balance, animal retention of dietary N and S increased by 7.0% and 2.4%, respectively, for each unit percent drop in crude protein fed animals, while C retention in the animal declined by 2.1%.

Dietary composition and particle size effects on swine manure characteristics and gas emissions

Nutrients excreted from animals affect the nutritive value of manure as a soil amendment as well as the composition of gases emitted from manure storage facilities. There is a dearth of information, however, on how diet type in combination with dietary particle size affects nutrients deposited into manure storage facilities and how this affects manure composition and gas emissions. To fill this knowledge gap, an animal feeding trial was performed to evaluate potential interactive effects between feed particle size and diet composition on manure characteristics and manure-derived gaseous emissions. Forty-eight finishing pigs housed in individual metabolism crates that allowed for daily collection of urine and feces were fed diets differing in fiber content and particle size. Urine and feces were collected and stored in 446-L stainless steel containers for 49 d. There were no interactive effects between diet composition and feed particle size on any manure or gas emission parameter measured. In general, diets higher in fiber content increased manure nitrogen (N), carbon (C), and total volatile fatty acid (VFA) concentrations and increased manure VFA emissions but decreased manure ammonia emissions. Decreasing the particle size of the diet lowered manure N, C, VFAs, phenolics, and indole concentrations and decreased manure emissions of total VFAs. Neither diet composition nor particle size affected manure greenhouse gas emissions.

Swine diets impact manure characteristics and gas emissions: Part II sulfur source

Sulfur is a key nutrient in swine diets and is associated with hydrogen sulfide (H₂S) emissions, odor, and respiratory distress of animals. Due to potential increases in S levels in swine diets by using alternative feedstuffs, a feeding trial study was conducted to determine the effect of dietary S source has on manure slurry chemical properties and gas emissions. A total of 24 gilts averaging 139 kg BW were fed a control diet formulated with corn and soybean meal (CSBM) containing 1.80 g S kg^-1 or diets containing 3.50 g S kg^-1 feed as supplied by calcium sulfate (CaSO₄), distillers dried grains with solubles (DDGS), or feather meal (CFM). Diets were fed for 41 d with an ADFI of 2.70 kg/d. Feces and urine were collected twice daily after each feeding and added to the manure storage containers. At the end of the study, manure slurries were monitored for gas emissions and chemical properties. Dietary S source had a significant effect on excretion of DM, C, N, and S in manure. Pigs fed the diets containing DDGS had significantly higher levels of NH₃, VFAs, and phenols in manure compared to pigs fed the CSBM diet. Pigs fed diets with organic S (i.e., DDGS and CFM) had lower emissions of H₂S compared to pigs fed the diet with inorganic sulfur (CaSO₄). In contrast, there were no significant differences in C or N emissions as affected by dietary treatment. Odor and odorant emissions differed by dietary treatment, with pigs fed the CFM diet having the highest odor emissions as compared to pigs fed the control CSBM diet. Pigs fed diets containing CFM and DDGS had a greater percentage of their chemical odor associated with volatile organic compounds while animals fed the CSBM diet or the diet with CaSO₄ had greater percentage associated with H₂S emissions.

Swine diets impact manure characteristics and gas emissions: Part I sulfur level

Sulfur is an essential nutrient for animal growth but is also associated with odor and morbidity of animals from swine operations. A study was conducted to determine the effects of increasing dietary S levels in swine diets on DM, pH, C, N, S, VFA, indole, and phenol concentrations in the manure, and on the emissions of C-, N-, and S-containing gases. A total of 24 gilts averaging 152 kg BW were fed diets containing 0.19, 0.30, 0.43, or 0.64% dietary S, as supplied by CaSO₄, for 31 d, with an ADFI of 3.034 kg d^-1. Feces and urine were collected after each feeding and added to manure storage containers. At the end of the study, manure slurries were monitored for gas emissions and chemical properties. Increasing dietary S lowered manure pH by 0.3 units and increased DM, N, and S by 10% for each 1.0 g S increase kg^-1 feed intake. Increased dietary S increased NH₃, sulfide, butanoic, and pentanoic acid concentrations in manure. Carbon and N emissions were not significantly impacted by dietary S, but S emissions in the form of hydrogen sulfide (H₂S) increased by 8% for each 1.0 g S increase kg^-1 feed intake. Odor increased by 2% for each 1.0 g increase of S consumed kg^-1 feed intake. Phenolic compounds and H₂S were the major odorants emitted from manure that increased with increasing dietary S.

Impact of narasin on manure composition, microbial ecology, and gas emissions from finishing pigs fed either a corn-soybean meal or a corn-soybean meal-dried distillers grains with solubles diets

An experiment was conducted to determine the effect of feeding finishing pigs a corn-soybean (CSBM) diet or a CSBM diet supplemented with 30% dried distillers grains with solubles (DDGS), in combination with or without a growth-promoting ionophore (0 or 30 mg narasin/kg of diet), has on manure composition, microbial ecology, and gas emissions. Two separate groups of 24 gilts (initial BW = 145.1 kg, SD = 7.8 kg) were allotted to individual metabolism crates that allowed for total but separate collection of feces and urine during the 48-d collection period. After each of the twice-daily feedings, feces and urine from each crate was collected and added to its assigned enclosed manure storage tank. Each tank contained an individual fan system that pulled a constant stream of air over the manure surface for 2 wk prior to air (day 52) and manure sampling (day 53). After manure sampling, the manure in the tanks was dumped and the tanks cleaned for the second group of pigs. Except for total manure Ca and P output as a percent of intake and for manure methane product rate and biochemical methane potential (P ≤ 0.08), there were no interactions between diet composition and narasin supplementation. Narasin supplementation resulted in increased manure C (P = 0.05), increased manure DM, C, S, Ca, and phosphorus as a percent of animal intake (P ≤ 0.07), and increased manure volatile solids and foaming capacity (P ≤ 0.09). No effect of narasin supplementation was noted on manure VFA concentrations or any of the gas emission parameters measured (P ≥ 0.29). In contrast, feeding finishing pigs a diet containing DDGS dramatically affected manure composition as indicated by increased concentration of DM, C, ammonia, N, and total and volatile solids (P = 0.01), increased manure DM, N, and C as a percent of animal intake (P = 0.01), increased manure total VFA and phenols (P ≤ 0.05), decreased gas emissions of ammonia and volatile sulfur compounds (VSC; P = 0.01), increased emissions of phenols and indoles (P ≤ 0.06), decreased methane production rate (P = 0.01), and slight differences in microbial ecology (R ≤ 0.47). In conclusion, feeding a diet which contains an elevated level of indigestible fiber (i.e., DDGS) resulted in more fiber in the manure which therefore dramatically affected manure composition, gas emissions, and microbial ecology, while narasin supplementation to the diet did not exhibit a significant effect on any of these parameters in the resultant swine manure.

Narasin effects on energy, nutrient, and fiber digestibility in corn-soybean meal or corn-soybean meal-dried distillers grains with solubles diets fed to 16-, 92-, and 141-kg pigs

Three experiments were conducted to determine the effect of narasin on growth performance and on GE and nutrient digestibility in nursery, grower, and finishing pigs fed either a corn-soybean meal (CSBM) diet or a CSBM diet supplemented with distillers dried grains with solubles (DDGS), in combination with either 0 or 30 mg narasin/kg of diet. In Exp. 1 (64 gilts, initial BW = 9.0 kg, SD = 1.0 kg) and Exp. 2 (60 gilts. initial BW = 81.1 kg, SD = 6.1 kg), gilts were allotted into individual pens and fed their experimental diets for 24 and 21 d, respectively. On the last 2 d of each experiment, fecal samples were collected to assess apparent total tract digestibility (ATTD) of GE and various nutrients. In Exp. 3, 2 separate groups of 24 gilts (initial BW = 145.1 kg, SD = 7.8 kg) were allotted to individual metabolism crates and fed their experimental diets for 30 d prior to a time-based 6-d total fecal collection period to assess GE and nutrient digestibility. In Exp. 1, there was an interaction between diet type and narasin addition for G:F and for many of the ATTD coefficients measured. When narasin was supplemented to the CSBM diet, ATTD of GE, DM, C, S, phosphorus, NDF, and ADF was either not changed or reduced, while when narasin was supplemented to DDGS diets, these same ATTD parameters were increased (interaction, ≤ 0.05). Even though ADG and ADFI were not affected, G:F was improved in pigs fed the CSBM diet with supplemental narasin, but was reduced in pigs fed the DDGS diet with supplemental narasin (interaction, < 0.05). In Exp. 2, there was an interaction between diet type and narasin supplementation only for ATTD of Ca (interaction, < 0.01), in that narasin supplementation did not change the ATTD of Ca in pigs fed the CSBM diet, while narasin supplementation reduced the ATTD of Ca in pigs fed the DDGS containing diet. In Exp. 3, there was an interaction between diet and narasin only for ATTD of C (interaction, < 0.01) in that narasin supplementation resulted in an increased ATTD of C in pigs fed the CSBM diet, while narasin supplementation to the DDGS containing diet resulted in a reduced ATTD of Ca. In general, the data indicate that narasin interacted with and had its largest effect on pig performance and GE or nutrient digestibility in 9 to 23 kg pigs compared to pigs weighing greater than 80 kg. The data also indicate that the addition of DDGS reduced GE, DM, Ca, and N digestibility, regardless of BW.

Microbial Community and Chemical Characteristics of Swine Manure during Maturation

Swine diet formulations have the potential to lower animal emissions, including odor and ammonia (NH). The purpose of this study was to determine the impact of manure storage duration on manure chemical and microbial properties in swine feeding trials. Three groups of 12 pigs were fed a standard corn-soybean meal diet over a 13-wk period. Urine and feces were collected at each feeding and transferred to 12 manure storage tanks. Manure chemical characteristics and headspace gas concentrations were monitored for NH, hydrogen sulfide (HS), volatile fatty acids, phenols, and indoles. Microbial analysis of the stored manure included plate counts, community structure (denaturing gradient gel electrophoresis), and metabolic function (Biolog). All odorants in manure and headspace gas concentrations were significantly ( < 0.01) correlated for length of storage using quadratic equations, peaking after Week 5 for all headspace gases and most manure chemical characteristics. Microbial community structure and metabolic utilization patterns showed continued change throughout the 13-wk trial. Denaturing gradient gel electrophoresis species diversity patterns declined significantly ( < 0.01) with time as substrate utilization declined for sugars and certain amino acids, but functionality increased in the utilization of short chain fatty acids as levels of these compounds increased in manure. Studies to assess the effect of swine diet formulations on manure emissions for odor need to be conducted for a minimum of 5 wk. Efforts to determine the impact of diets on greenhouse gas emissions will require longer periods of study (>13 wk).

Impact of fiber source and feed particle size on swine manure properties related to spontaneous foam formation during anaerobic decomposition

Foam accumulation in deep-pit manure storage facilities is of concern for swine producers because of the logistical and safety-related problems it creates. A feeding trial was performed to evaluate the impact of feed grind size, fiber source, and manure inoculation on foaming characteristics. Animals were fed: (1) C-SBM (corn-soybean meal): (2) C-DDGS (corn-dried distiller grains with solubles); and (3) C-Soybean Hull (corn-soybean meal with soybean hulls) with each diet ground to either fine (374 μm) or coarse (631 μm) particle size. Two sets of 24 pigs were fed and their manure collected. Factors that decreased feed digestibility (larger grind size and increased fiber content) resulted in increased solids loading to the manure, greater foaming characteristics, more particles in the critical particle size range (2-25 μm), and a greater biological activity/potential.

Lab-assay for estimating methane emissions from deep-pit swine manure storages

Methane emission is an important tool in the evaluation of manure management systems due to the potential impact it has on global climate change. Field procedures used for estimating methane emission rates require expensive equipment, are time consuming, and highly variable between farms. The purpose of this paper is to report a simple laboratory procedure for estimating methane emission from stored manure. The test developed was termed a methane production rate (MPR) assay as it provides a short-term biogas production measurement. The MPR assay incubation time is short (3d), requires no sample preparation in terms of inoculation or dilution of manure, is incubated at room temperature, and the manure is kept stationary. These conditions allow for high throughput of samples and were chosen to replicate the conditions within deep-pit manure storages. In brief, an unaltered aliquot of manure was incubated at room temperature for a three-days to assay the current rate of methane being generated by the manure. The results from this assay predict an average methane emission factor of 12.2 ± 8.1 kg CH4 head(-1) yr(-1) per year, or about 5.5 ± 3.7 kg CH4 per finished animal, both of which compare well to literature values of 5.5 ± 1.1 kg CH4 per finished pig for deep-pit systems (Liu et al., 2013). The average methane flux across all sites and months was estimated to be 22 ± 17 mg CH4 m(-2)-min(-1), which is within literature values for deep-pit systems ranging from 0.24 to 63 mg CH4 m(-2)-min(-1) (Park et al., 2006) and similar to the 15 mg CH4 m(-2)-min(-1) estimated by (Zahn et al., 2001).

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 US. 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 microg/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.

Concentrations of particulate matter emitted from large cattle feedlots in Kansas

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 microm, indicating that particles that were emitted from the feedlots were generally large in size.

Managing agricultural emissions to the atmosphere: state of the science, fate and mitigation, and identifying research gaps

The impact of agriculture on regional air quality creates significant challenges to sustainability of food supplies and to the quality of national resources. Agricultural emissions to the atmosphere can lead to many nuisances, such as smog, haze, or offensive odors. They can also create more serious effects on human or environmental health, such as those posed by pesticides and other toxic industrial pollutants. It is recognized that deterioration of the atmosphere is undesirable, but the short- and long-term impacts of specific agricultural activities on air quality are not well known or understood. These concerns led to the organization of the 2009 American Chemical Society Symposium titled . An outcome of this symposium is this special collection of 14 research papers focusing on various issues associated with production agriculture and its effect on air quality. Topics included emissions from animal feeding operations, odors, volatile organic compounds, pesticides, mitigation, modeling, and risk assessment. These papers provide new research insights, identify gaps in current knowledge, and recommend important future research directions. As the scientific community gains a better understanding of the relationships between anthropogenic activities and their effects on environmental systems, technological advances should enable a reduction in adverse consequences on the environment.

Dietary protein and cellulose effects on chemical and microbial characteristics of Swine feces and stored manure

The objectives of this study were to investigate the effects of dietary crude protein (14.5 or 12.0%) and cellulose (8.7 or 2.5%) levels on composition of feces and manure after 8 wk of diet feeding and storage. Pigs were fed twice daily; after each feeding, urine and feces were collected and added to manure storage containers. On weeks 2 and 8 after initiation of the experiment, fresh fecal and manure samples were obtained. On Week 8, increased dietary cellulose resulted in significantly higher levels of volatile fatty acids (VFA) and phenols in feces compare to other diets. In contrast, dietary protein had the greatest effect on manure chemical composition; lower protein decreased sulfur content, ammonia, and phenolic compound concentrations. High levels of either dietary cellulose or protein tended to increase microbial community similarity in fecal samples, but only high protein increased similarity among manure sample microbial communities. Fecal and manure samples from Week 8 differed from samples taken in Week 2 both in chemical and microbiological composition. Week 2 samples had lower concentrations of many of chemical compounds and microbial diversity than samples from Week 8. The fecal results indicate that after 2 wk of feeding experimental diets the animals were not fully adapted to the diets. More importantly, after only 2 wk of urine and fecal collection, manure was not representative of stored manure, limiting its usefulness in developing standards and recommendations for on-farm management practices.

Field sampling method for quantifying odorants in humid environments

Most air quality studies in agricultural environments use thermal desorption analysis for quantifying semivolatile organic compounds (SVOCs) associated with odor. The objective of this study was to develop a robust sampling technique for measuring SVOCs in humid environments. Test atmospheres were generated at ambient temperatures (23 +/- 1.5 degrees C) and 25, 50, and 80% relative humidity (RH). Sorbent material used included Tenax, graphitized carbon, and carbon molecular sieve (CMS). Sorbent tubes were challenged with 2, 4, 8, 12, and 24 L of air at various RHs. Sorbent tubes with CMS material performed poorly at both 50 and 80% RH dueto excessive sorption of water. Heating of CMS tubes during sampling or dry-purging of CMS tubes post sampling effectively reduced water sorption with heating of tubes being preferred due to the higher recovery and reproducibility. Tenaxtubes had breakthrough of the more volatile compounds and tended to form artifacts with increasing volumes of air sampled. Graphitized carbon sorbent tubes containing Carbopack X and Carbopack C performed best with quantitative recovery of all compounds at all RHs and sampling volumes tested. The graphitized carbon tubes were taken to the field for further testing. Field samples taken from inside swine feeding operations showed that butanoic acid, 4-methylphenol, 4-ethylphenol, indole, and 3-methylindole were the compounds detected most often above their odor threshold values. Field samples taken from a poultry facility demonstrated that butanoic acid, 3-methylbutanoic acid, and 4-methylphenol were the compounds above their odor threshold values detected most often, relative humidity, CAFO, VOC, SVOC, thermal desorption, swine, poultry, air quality, odor.

Alcohol, volatile fatty acid, phenol, and methane emissions from dairy cows and fresh manure

There are approximately 2.5 million dairy cows in California. Emission inventories list dairy cows and their manure as the major source of regional air pollutants, but data on their actual emissions remain sparse, particularly for smog-forming volatile organic compounds (VOCs) and greenhouse gases (GHGs). We report measurements of alcohols, volatile fatty acids, phenols, and methane (CH4) emitted from nonlactating (dry) and lactating dairy cows and their manure under controlled conditions. The experiment was conducted in an environmental chamber that simulates commercial concrete-floored freestall cow housing conditions. The fluxes of methanol, ethanol, and CH4 were measured from cows and/or their fresh manure. The average estimated methanol and ethanol emissions were 0.33 and 0.51 g cow(-1) h(-1) from dry cows and manure and 0.7 and 1.27 g cow(-1) h(-1) from lactating cows and manure, respectively. Both alcohols increased over time, coinciding with increasing accumulation of manure on the chamber floor. Volatile fatty acids and phenols were emitted at concentrations close to their detection limit. Average estimated CH4 emissions were predominantly associated with enteric fermentation from cows rather than manure and were 12.35 and 18.23 g cow(-1) h(-1) for dry and lactating cows, respectively. Lactating cows produced considerably more gaseous VOCs and GHGs emissions than dry cows (P < 0.001). Dairy cows and fresh manure have the potential to emit considerable amounts of alcohols and CH4 and research is needed to determine effective mitigation.

Bias of Tedlar bags in the measurement of agricultural odorants

Odor regulations typically specify the use of dynamic dilution olfactometery (DDO) as a method to quantify odor emissions, and Tedlar bags are the preferred holding container for grab samples. This study was conducted to determine if Tedlar bags affect the integrity of sampled air from animal operations. Air samples were collected simultaneously in both Tedlar bags and Tenax thermal desorption tubes. Sample sources originated from either a hydrocarbon-free air tank, dynamic headspace chamber (DHC), or swine-production facility, and were analyzed by gas chromatography-mass spectrometry-olfactometry (GC-MS-O). Several background contaminants were identified from Tedlar bags, which included the odorous compounds N,N-dimethyl acetamide (DMAC), acetic acid, and phenol. Samples from the DHC demonstrated that recovery of malodor compounds was dependent on residence time in the Tedlar bag with longer residence time leading to lower recovery. After 24 h of storage, recovery of C3-C6 volatile fatty acids (VFA) averaged 64%, 4-methylphenol and 4-ethylphenol averaged 10%, and indole and 3-methylindole were below the detection limits of GC-MS-O. The odor activity value (OAV) of grab samples collected in Tedlar bags were 33 to 65% lower following 24 h of storage. These results indicate that significant odorant bias occurs when using Tedlar bags for the sampling of odors from animal production facilities.

Manure composition of swine as affected by dietary protein and cellulose concentrations1

An experiment was conducted to investigate the effects of reducing dietary CP and increasing dietary cellulose concentrations on manure DM, C, N, S, VFA, indole, and phenol concentrations. Twenty-two pigs (105 kg initial BW) were fed diets containing either 14.5 or 12.0% CP, in combination with either 2.5 or 8.7% cellulose. Pigs were fed twice daily over the 56-d study, with feed intake averaging 2.74 kg/d. Feces and urine were collected after each feeding and added to the manure storage containers. Manure storage containers were designed to provide a similar unit area per animal as found in industry (7,393 cm2). Before sampling on d 56, the manure was gently stirred to obtain a representative sample for subsequent analyses. An interaction of dietary CP and cellulose was observed for manure acetic acid concentration, in that decreasing CP lowered acetic acid in pigs fed standard levels of cellulose but increased acetic acid in pigs fed greater levels of cellulose (P = 0.03). No other interactions were noted. Decreasing dietary CP reduced manure pH (P = 0.01), NH4 (P = 0.01), isovaleric acid (P = 0.06), phenol (P = 0.05), and 4-ethyl phenol (P = 0.02) concentrations. Increasing dietary cellulose decreased pH (P = 0.01) and NH4 (P = 0.07) concentration but increased manure C (P = 0.03), propionic acid (P = 0.01), butyric acid (P = 0.03), and cresol (P = 0.09) concentrations in the manure. Increasing dietary cellulose also increased manure DM (P = 0.11), N (P = 0.11), and C (P = 0.02) contents as a percentage of nutrient intake. Neither cellulose nor CP level of the diet affected manure S composition or output as a percentage of S intake. Headspace N2O concentration was increased by decreasing dietary CP (P = 0.03) or by increasing dietary cellulose (P = 0.05). Neither dietary CP nor cellulose affected headspace concentration of CH4. This study demonstrates that diets differing in CP and cellulose content can significantly impact manure composition and concentrations of VFA, phenol, and indole, and headspace concentrations of N(2)O, which may thereby affect the environmental impact of livestock production on soil, air, and water.

Effects of soil storage on the microbial community and degradation of metsulfuron-methyl

The effect storage had on the microbial biomass in two soils (Trevino and Fargo) was compared to the effect storage had on each soil's capacity to degrade metsulfuron-methyl. Soils were collected from the field and used fresh (<3 weeks old) or stored at 20 and 4 degrees C for 3 or 6 months. The phospholipid fatty acid content of the soils was used to monitor changes in the microbial biomass during storage and incubation in a flow-through apparatus. In both soils, [phenyl-U-14C]metsulfuron-methyl was used to monitor changes in the route and rate of degradation along with 14CO2 evolution (mineralization). Total microbial biomasses in both soils were significantly reduced for soils incubated in the flow-through apparatus, whereas only the Trevino soil's microbial biomass was significantly reduced as a result of storage. The microbial communities of both soils were significantly different as a result of storage as shown by discriminant analysis. In both soils, degradation rate, pathway of degradation, and mineralization of metsulfuron-methyl were significantly affected by storage compared to fresh soil. The half-life of metsulfuron-methyl increased significantly (P < 0.05) in the Trevino soil from 45 days (fresh) to 63 days (stored soil), whereas in the Fargo soil half-lives increased significantly (P < 0.05) from 23 days (fresh) to 29 days (soils stored for 6 months). In both soils, mineralization of [14C]metsulfuron-methyl was significantly (P < 0.05) higher in fresh soils compared to stored soils. The degradation pathways of metsulfuron-methyl changed with storage as evidenced by the loss of formation of one biologically derived metabolite (degradate) in stored soils compared to fresh soils.

Carbofuran degradation in soil profiles

Two soils, Puyallup fine sandy loam from Puyallup, WA, and Ellzey fine sand from Hastings, FL, each with a prior history of carbofuran exposure but with different pedological and climatological characteristics, were found to exhibit enhanced degradation toward carbofuran in surface and subsurface soil layers. The treated Puyallup and Ellzey soils exhibited higher mineralization rates for both the carbonyl and the aromatic ring of carbofuran when compared to untreated soils. Disappearance rates of [14C-URL (uniformly ring labeled)] carbofuran in the treated Ellzey soil was faster than in untreated soil, and also faster in surface soil than in subsurface soil. Initial degradation patterns in the treated Ellzey soil were also different from those in the untreated soil. The treated Ellzey soil degraded carbofuran mainly through biological hydrolysis, while untreated soil degraded carbofuran through both oxidative and hydrolytic processes.