Robin C. Brandt

Effect of Origanum vulgare L. leaves on rumen fermentation, production, and milk fatty acid composition in lactating dairy cows

This experiment investigated the effects of dietary supplementation of Origanum vulgare L. leaf material (OR) on rumen fermentation, production, and milk fatty acid composition in dairy cows. The experimental design was a replicated 4 × 4 Latin square with 8 rumen-cannulated Holstein cows and 20-d experimental periods. Treatments were control (no OR supplementation), 250 g/cow per day OR (LOR), 500 g/d OR (MOR), and 750 g/d OR (HOR). Oregano supplementation had no effect on rumen pH, volatile fatty acid concentrations, and estimated microbial protein synthesis, but decreased ammonia concentration and linearly decreased methane production per unit of dry matter intake (DMI) compared with the unsupplemented control: 18.2, 16.5, 11.7, and 13.6g of methane/kg of DMI, respectively. Proportions of rumen bacterial, methanogen, and fungal populations were not affected by treatment. Treatment had no effect on total-tract apparent digestibility of dietary nutrients, except neutral detergent fiber digestibility was slightly decreased by all OR treatments compared with the control. Urinary N losses and manure odor were not affected by OR, except the proportion of urinary urea N in the total excreted urine N tended to be decreased compared with the control. Oregano linearly decreased DMI (28.3, 28.3, 27.5, and 26.7 kg/d for control, LOR, MOR, and HOR, respectively). Milk yield was not affected by treatment: 43.4, 45.2, 44.1, and 43.4 kg/d, respectively. Feed efficiency was linearly increased with OR supplementation and was greater than the control (1.46, 1.59, 1.60, and 1.63 kg/kg, respectively). Milk composition was unaffected by OR, except milk urea-N concentration was decreased. Milk fatty acid composition was not affected by treatment. In this short-term study, OR fed at 250 to 750 g/d decreased rumen methane production in dairy cows within 8h after feeding, but the effect over a 24-h feeding cycle has not been determined. Supplementation of the diet with OR linearly decreased DMI and increased feed efficiency. Oregano had no effects on milk fatty acid composition.

Managing biosolids runoff phosphorus using buffer strips enhanced with drinking water treatment residuals.

Vegetated buffers strips typically have limited ability to reduce delivery of dissolved phosphorus (DP) from agricultural fields to surface waters. A field study was conducted to evaluate the ability of buffer strips enhanced with drinking water treatment residuals (WTRs) to control runoff P losses from surface-applied biosolids characterized by high water-extractable P (4 g kg(-)(1)). Simulated rainfall (62.4 mm h(-1)) was applied to grassed plots (3 m x 10.7 m including a 2.67 m downslope buffer) surface-amended with biosolids at 102 kg P ha(-1) until 30 min of runoff was collected. With buffer strips top-dressed with WTR (20 Mg ha(-1)), runoff total P (TP = 2.5 mg L(-1)) and total DP (TDP = 1.9 mg L(-1)) were not statistically lower (alpha = 0.05) compared to plots with unamended grass buffers (TP = 2.7 mg L(-1); TDP = 2.6 mg L(-1)). Although the applied WTR had excess capacity (Langmuir P maxima of 25 g P kg(-1)) to sorb all runoff P, kinetic experiments suggest that sheet flow travel time across the buffers ( approximately 30 s) was insufficient for significant P reduction. Effective interception of dissolved P in runoff water by WTR-enhanced buffer strips requires rapid P sorption kinetics and hydrologic flow behavior ensuring sufficient runoff residence time and WTR contact in the buffer. Substantial phosphate-adsorbent contact opportunity may be more easily achieved by incorporating WTRs into P-enriched soils or blending WTRs with applied P sources.

Amendments for mitigation of dairy manure ammonia and greenhouse gas emissions: Preliminary screening

Amendments can be practical and cost-effective for reducing ammonia [NH3] and greenhouse gas [GHG] emissions from dairy manure. In this study, the effect of 22 amendments on NH3 and GHG carbon dioxide [CO2], methane [CH4] and nitrous oxide [N2O] emissions from dairy manure were simultaneous investigated at room temperature (20oC). Dairy manure slurry (2 kg; 1:1.7 urine:feces; 12% total solids) was treated with various amendments, representing different classes of product, following the suppliers’ recommended rates. In this screening of products, one sample of each amendment was evaluated along with untreated manure slurry with repeated measurements over 24 h. Gas emissions were measured after short (3 d) and medium (30 d) storage duration using a photoacoustic multi-gas analyzer. Six amendment products that acted as microbial digest, oxidizing agent, masking agent or adsorbent significantly reduced NH3 by >10% (P = 0.04 to <0.001) after both 3 and 30 d. Microbial digest/enzymes with nitrogen substrate appeared effective in reducing CH4 fluxes for both storage times. Most of the masking agents and disinfectants significantly increased CH4 in both storage periods (P = 0.04 to <0.001). For both CH4 and CO2 fluxes, aging the manure slurry for 30 d significantly reduced gas production by 11 to 100% (P <0.001). While some products reduced emissions at one or both storage times, results showed that the ability of amendments to mitigate emissions from dairy manure is finite and re-application may be required even for a static amount of manure. Simultaneous measurement of gases identified glycerol as a successful NH3 reduction agent while increasing CH4 in contrast to a digestive-microbial product that significantly reduced CH4 while enhancing NH3 release.

Developing an Environmental Manure Test for the Phosphorus Index

Abstract Widespread implementation of the phosphorus (P) index has focused attention on environmental manure tests that can be used to estimate the relative availability of P in manure to runoff water. This article describes the development and use of a water extractable P (WEP) test to assess the capacity of land‐applied manure to enrich P in runoff water. WEP of surface‐applied manure has been shown to be strongly correlated to dissolved P concentrations in runoff from agricultural soils. WEP tests that have a defined water‐to‐manure‐solids ratio and involve extraction times of 30 to 120 min provide the best prediction of dissolved P in runoff across a wide range of manures. Consistent measurement of manure WEP can be achieved with manure sample storage times of up to 22 days (4°C), acidified extract holding times of 18 days, and solid separation by either centrifugation or paper filtration. Reproducibility of WEP tests is comparable to that of other common manure tests (e.g., total P), as verified by within‐laboratory and inter laboratory evaluations. A survey of 140 livestock manures revealed significant differences in mean WEP among different livestock manures, with swine greater than poultry (turkey, broiler and layer chickens) and dairy cattle greater than beef cattle. Such results support the use of WEP‐based coefficients to modify the source component of the P index.

MULTIPLE-CHAMBER INSTRUMENTATION DEVELOPMENT FOR COMPARING GAS FLUXES FROM BIOLOGICAL MATERIALS

The complex and often confounding factors that influence gas emission from biological materials require a measurement procedure that is precise, accurate, repeatable, and reliable. A multiple-chamber instrumentation system was developed to rapidly and precisely measure gas emission potential from multiple sources, such as manure and biosolids, to compare gas emission reduction potential of various treatments. Up to eight steady-state flux chambers, a photoacoustic multi-gas monitor, and a hydrogen sulfide pulsed fluorescence analyzer were coupled through a multiplexer relay to measure concentrations of ammonia and hydrogen sulfide, respectively. Depending on the number of chambers used, gas concentration in the chambers was measured on 20- to 72-min intervals over a nominal 24-h period via fully-automated data collection software. Built-in quality controls allowed potential cross-contamination to be quickly identified in order to maintain the precision of the instrument. Air flow rate in each chamber was maintained at 0.5 air changes per minute using calibrated flow meters. The performance of the multiple chamber system in evaluating ammonia gas flux was tested using ammonia calibration gas (accuracy; 97.3% recovery through the system) and freestall barn-floor manure sub-samples (precision 8% for biologically heterogeneous material; standard error of 2% of mean). Using separately-collected dairy cow urine and feces the instrument system was used to evaluate impact of source depth showing an apparent slight reduction of ammonia release with increasing depth but findings were within the expected precision range of the instrument for this type of material. An example demonstrating the multiple-chamber system use in evaluating ammonia flux processes evaluated urine and feces mixed to five ratios ranging from 10:90 to 90:10. The 50:50 ratio had the highest cumulative emission over 23 h. Removing ammonia with a scrubber and moisture via condensation trap significantly improved the accuracy of hydrogen sulfide concentration measurements when analyzing dairy manure slurry. Odorous air samples were easily collected from each chamber headspace and evaluated using triangular forced-choice dynamic olfactometry and odor-quality assessments for simultaneous gas emission and odor evaluation. This instrumentation system offers repeatable, concurrent monitoring of gas and odor emission from biological sources and provides a powerful tool for gas emission research and evaluation of management practices directed at reducing gas release.

Neutral ammonium citrate extraction of biosolids phosphorus

Abstract Matching biosolids application rates to crop phosphorus (P) needs requires quantifying the P fertilizer replacement value of biosolids. Neutral ammonium citrate (NAC) extraction of P, used for assessing available P in mineral fertilizers, was evaluated for 35 different biosolids. Biosolids NAC‐P was not statistically different (p=0.05) from total P using strong acid digestion (EPA 3051‐P). High P recovery by NAC was attributed to dissolution of P‐containing iron (Fe)/aluminum (Al) oxides under the aggressive extracting conditions (0.88 M citrate at 65°C). Citrate effectively dissolves P‐binding Fe/Al hydrous oxides, the very components that reduce phytoavailability when biosolids are land applied. Greenhouse studies with pasture grass (Paspalum notatum Flugge) grown in P‐deficient soils amended with biosolids revealed P phytoavailability was not correlated (r2=0.10) with biosolids NAC‐P. Phytoavailability was inversely correlated (r2=0.66) with biosolids total Al+Fe content. The NAC extraction, designed for commercial fertilizers, is inappropriate for quantifying biosolids phytoavailable P.

Effects of forage-to-concentrate ratio and dietary fiber manipulation on gas emissions and olfactometry from manure of Holstein heifers

The objective of this experiment was to determine the effects of differing ratios of forage to concentrate (F:C) and fiber levels on odor and gas emissions from manure. Eight Holstein dairy heifers (362.45±4.53 d of age and 335.6±7.41 kg of body weight) were randomly assigned to a split-plot, 4×4 Latin square design (21-d periods) with F:C as the whole plot (20 or 80% forage) and fiber level as sub-plot (0, 20, 40, or 60% inclusion of corn stover). Gas concentration was determined using an infrared photoacoustic analyzer over a 24-h period using a steady-state flux chamber setup. Odorous air samples were collected from chamber headspace and evaluated by 6 human assessors using a forced-choice dynamic olfactometry technique. Emissions of CO2 were greater for the low than high concentrate diets, and no differences were observed for NH3 and CH4 emissions between F:C. Although F:C had no effect on NH3 emissions, as dietary fiber increased, a linear interaction with opposite effects was found for high and low concentrate diets. Nitrous oxide emissions were below minimum detectable levels. Neither F:C nor neutral detergent fiber level affected odor intensity. Odor emissions were successfully assessed, and manipulation of dietary fiber has the potential to influence CH4 and NH3 emissions.

Amendments for mitigation of odor emissions from dairy manure: Preliminary screening

Manure amendments have shown variable effectiveness in reducing odor. Twenty-two amendments were evaluated for dairy manure odor stored at 20oC for 3 d and 30 d. Amendments represented different classes of product including microbial, oxidizing agent, disinfectant, masking agent, and adsorbent. Each amendment was added to 2 kg dairy manure (1:1.7 urine:feces, 12% total solids) following recommended rates. In this preliminary screening, one sample (n=1) of each amendment was evaluated along with untreated manure (Control). Odor emissions from each amendment and Control was estimated twice by five qualified odor assessors (n=10) after each storage duration following an international standard method for Triangular Forced-Choice Olfactometry. Odor quality was quantified using a hedonic tone scale, a Labeled Magnitude Scale and ASTM methods for suprathreshold odor intensity and an odor character wheel for description. Odor emissions were significantly reduced at 30 d versus 3 d incubation (P<0.0001) with no amendment effective for both incubation times. Likewise, for all amendments tested, aging the manure slurry for 30 d reduced malodor and odor intensity by 10 to 105% (P<0.0001). A microbial digest/enzyme product (proprietary), disinfectant (hydrogen peroxide) and masking agent (Hyssopus officinalis essential oil) provided significant short-term control of odor (P <0.0001). However, after 30 d, only a proprietary microbial aerobic/facultative product and a proprietary mix of chemicals, both with weekly re-application, retained efficacy. Hedonic tone indicated an improvement to “slightly to moderately unpleasant” smell versus untreated manure for all amendments except clinoptilolite zeolite. Hedonic tone improvement was correlated with reduced manure odor intensity.

Operator Exposure to Hydrogen Sulfide from Dairy Manure Storages Containing Gypsum Bedding

Dairy manure storages containing gypsum-based bedding have been linked anecdotally with injury and death due to presumed dangerous levels of gases released. Recycled gypsum products are used as a cost-effective bedding alternative to improve animal welfare and provide agronomic benefits to manure recycled back to the land. Sulfur contained in gypsum (calcium sulfate) can contribute to hydrogen sulfide (H2S) gas formation under the anaerobic storage conditions typical of dairy manure slurry. Disturbance of stored manure during agitation releases a burst of volatile gases. On-farm monitoring was conducted to document conditions during manure storage agitation relative to gas concentration and operator safety. One objective was to document operator exposure to H2S levels; therefore, each operator wore a personal gas monitor while performing tasks associated with manure storage agitation. Data from three dairy bedding management categories on ten farms were compared: (1) traditional organic bedding, (2) gypsum bedding, and (3) gypsum bedding plus a manure additive thought to reduce H2S formation and/or release. Portable meters placed around the perimeter of dairy manure storages recorded H2S concentrations prior to and during 19 agitation events. Results show that farms using gypsum bedding produced higher H2S concentrations during manure storage agitation than farms using traditional bedding. In most cases, gypsum-containing manure storages produced H2S levels above recognized safe thresholds for both livestock and humans. Farm operators were most at risk during activities in close proximity to the manure storage during agitation, and conditions 10 m away from the storage were above the 20 ppm H2S threshold on some farms using gypsum bedding. Although H2S concentrations rose to dangerous levels, only two of 18 operators were exposed to >50 ppm H2S during the first 60 min of manure storage agitation. Operators who are aware of the risk of high H2S concentrations near gypsum-laden manure storages can reduce their exposure risk by working upwind and away from the H2S plume within a closed tractor cab.

Field Olfactometry Assessment of Dairy Manure Land Application Methods

Because odor potential is poorly correlated with measured concentrations of component gases, human sensory assessment (olfactometry) remains the ultimate means for quantifying agricultural odors. Field olfactometry measurements vary with wind velocity and source distance. To minimize this variability, dairy manure slurry was applied in a 10-ft swath to grassland in 200-foot diameter circles. Nasal Ranger® Field Olfactometer (NRO) instruments were used to collect dilution-to-threshold (D/T) observations from the center of each circle using four odor assessors taking four readings each over a 10-min period. The Best Estimate Threshold D/T (BET10) was calculated for five manure application methods and an untreated control. Field odor panel observations were performed before application and at aeration infiltration > surface + chisel incorporation > direct ground injection ˜ shallow disk injection > control, which closely followed laboratory TFC odor panel results (r = 0.83). We conclude field olfactometry can be useful for quantifying agricultural odor emissions but multiple assessors and observations, strict compliance with established protocols, and careful data analysis are essential.