Modeling ammonia emissions from manure in conventional, organic, and grazing dairy systems and practices to mitigate emissions

Almost 60% of all ammonia (NH3) emissions are from livestock manure. Understanding the sources and magnitude of NH3 emissions from manure systems is critical to implement mitigation strategies. This study models 13 archetypical conventional (5 farms), organic (5 farms), and grazing (3 farms) dairy farms to estimate NH3 emissions from manure at the barn, storage, and after land application. Mitigation practices related to management of the herd, crop production, and manure are subsequently modeled to quantify the change in NH3 emissions from manure by comparing archetypical practices with these alternative practices. A mass balance of nutrients is also conducted. Emissions per tonne of excreted manure for the manure system (barn, storage, and land application) range from 3.0 to 4.4 g of NH3 for conventional farms, 3.5 to 4.4 g of NH3 for organic farms, and 3.4 to 3.9 g of NH3 for grazing farms. For all farm types, storage and land application are the main sources of NH3 emissions from manure. In general, solid manures have higher emission intensities due to higher pH during storage (pH = 7.4 for liquid, 7.8 for slurry, and 8.5 for solid manure) and lower infiltration rates after land application when compared with slurry and liquid manures. The most effective management practices to reduce NH3 emissions from manure systems are combining solid-liquid separation with manure injection (up to 49% reduction in NH3 emissions), followed by injection alone, and reducing crude protein in the dairy ration, especially in organic and grazing farms that have grazing and forages as the main component of the dairy ration. This study also shows that the intensity of NH3 emissions from manure depends significantly on the functional unit and presents results per manure excreted, total solids in excreted manure, animal units, and fat- and protein-corrected milk.

Effect of diets with different crude protein levels on ammonia and greenhouse gas emissions from a naturally ventilated dairy housing

Less crude protein (CP) in the diet can reduce nitrogen excretion of dairy cattle and lower their ammonia (NH3) and nitrous oxide (N2O) formation potential. The diet composition might also affect emissions of methane (CH4) and carbon dioxide (CO2). However, previous studies did not investigate the effect of diets with different CP levels that are customary practice in Switzerland on NH3 and greenhouse gas emissions on a practical scale. In a case-control approach, we quantified the emissions (NH3, N2O, CH4, CO2) in two separate but identical compartments of a naturally ventilated cubicle housing for lactating dairy cows over six days by using a tracer ratio method. Cows in one compartment received a diet with 116 g CP per kilogram dry matter (DM), in the other compartment with 166 g CP kg-1 DM. Subsequently, diets were switched for a second 6-day measurement phase. The results showed that the diet, aside from outside temperature and wind speed in the housing, was driving NH3 and N2O emissions. NH3 and N2O emission reduction per livestock unit (LU) was on average 46 % and almost 20 %, respectively, for the diet with low CP level compared to the higher CP level. In addition, strong relationships were observed between the CP content of the diet, N excretion in the urine and the milk urea content. An increased temperature or wind speed led to a clear increase in NH3 emissions. Differences in CH4 and CO2 emissions per LU indicated a significant influence of the diet, which cannot be attributed to the CP content. Our herd-level study demonstrated that a significant reduction in NH3 and N2O emissions related to LU, energy-corrected milk as well as DM intake can be achieved by lowering the CP content in the diet.

Effect of source and level of forage in the diet on in vitro ammonia emission from manure of Holstein and Jersey dairy cows

Reducing overall reactive N losses from dairy production systems depends substantially on reducing the atmospheric emission of manure ammonia (NH₃). The objective of this study was to determine potential NH₃-N emission of reconstituted manure using an in vitro protocol. Feces and urine were collected from a companion study designed as a Latin square in which 4 Holstein and 4 Jersey cows were fed diets containing 2 levels of forage neutral detergent fiber (NDF) [low-forage NDF (19%) vs. high-forage NDF (24%; dry matter basis)] from either alfalfa silage or corn silage (70:30 vs. 30:70 ratio of alfalfa silage NDF:corn silage NDF) arranged as a 2 × 2 factorial. All diets contained similar levels of crude protein (17%) and starch (23%), and had forage-to-concentrate ratios of 55:45 and 68:32 for low- and high-forage NDF diets, respectively. Measurements of NH₃-N emission were conducted in a laboratory-scale chamber with 16 g of reconstituted manure (urine plus feces) incubated for 48 h at 15°C with sampling at 1, 3, 6, 12, 24, 36, and 48 h. Hourly NH₃-N emissions data were analyzed using a repeated-measures mixed model in R (https://www.r-project.org/). The fixed effects were breed, forage NDF level, forage NDF source, time of sampling, and all possible interactions; cow was included as a random term. The cumulative 48-h NH₃-N emissions and the scaled-up emissions accounting for daily output of manure from each cow were analyzed using the same model but without time of sampling. Level and source of forage in the diet tended to influence the pattern in hourly rate and 48-h cumulative emission, respectively. Accounting for daily manure volume differences, low-forage NDF diets led to lower estimates of daily NH₃-N emissions than high-forage NDF diets (20% on a cow basis, 15% on a raw manure basis, and 18% on a manure-N basis). Compared with Holsteins, Jerseys emitted 17% lower estimated NH₃-N on a cow basis, mainly due to lower manure excretion but tended to emit 15% more NH₃-N expressed on a manure-N basis. Findings of this study suggested that cow breed and dietary forage NDF level should be considered in the prediction of NH₃-N emission from the dairy industry.

Study of nitrogen fluxes across conventional solid floor cubicle and compost-bedded pack housing systems in dairy cattle barns located in the Mediterranean area: Effects of seasonal variation

The aim of this study was to determine the effect of housing system (or manure management system) and season on manure N recovery and volatilization using an N mass balance. Dietary, milk, and manure N were monitored together with outside temperatures in 6 dairy barns. Three barns were designed as conventional freestalls (cubicle, CUB) with an automatic manure scraper system and concrete floor, in which the gutter in the middle was continuously scraped (every 2-4 h) and the slurry was conveyed toward an open-air concrete pool. The other 3 barns were designed as a loose housing system (HS) with a compost-bedded pack (CB) and conventional confinement housing provided with a feed alley that was cleaned mechanically (2-3 times per day). The farms under study were located near Lleida in the center of the Ebro valley, in northeastern Spain. Nitrogen recovery was measured twice under farm-like conditions either during spring-summer (3 mo of increasing temperatures) or fall-winter (3 mo of decreasing temperatures). The number of cows per barn ranged from 99 to 473, and average age, mean lactation, and parturition intervals were 4.1 yr, 2.43 lactations, and 426.6 d, respectively. In spring-summer, animals ate more [26.3 vs. 23.8 kg of dry matter (DM)/d] and produced more milk (34.6 vs. 31.3 kg/d ± 0.68). However, milk composition did not change. Stored manure from the CB system showed a higher DM concentration with respect to the CUB system (379.15 vs. 97.65 g/kg of fresh matter); however, N (31.45 vs. 40.2), NH₃-N (5.3 vs. 18.9) and its ratios with phosphorus (NH₃-N:P, 3.52 vs. 5.2) and potassium (NH₃-N:K, 0.615 vs. 2.69) showed the opposite trend. No differences were found in N intake (653 vs. 629.5 g/d) or milk N secretion (190 vs. 177.8 g/d for CUB and CB barns, respectively) although net N recovery of the excreted N (N_intake - N_Milk) was significantly lower in manure in CB barns than in CUB systems (193.8 vs. 389.3 g/d). The proportion of N irreversible loss in relation to the N intake was higher in CB than in CUB barns (42.3 vs. 11.0%). There was no clear association between season and irreversible N losses; however, the housing system was pivotal in the association between N recovery in manure and irreversible losses by volatilization.

Mitochondrial DNA Mutation, Diseases, and Nutrient-Regulated Mitophagy

A wide spectrum of human diseases, including cancer, neurodegenerative diseases, and metabolic disorders, have been shown to be associated with mitochondrial dysfunction through multiple molecular mechanisms. Mitochondria are particularly susceptible to nutrient deficiencies, and nutritional intervention is an essential way to maintain mitochondrial homeostasis. Recent advances in genetic manipulation and next-generation sequencing reveal the crucial roles of mitochondrial DNA (mtDNA) in various pathophysiological conditions. Mitophagy, a term coined to describe autophagy that targets dysfunctional mitochondria, has emerged as an important cellular process to maintain mitochondrial homeostasis and has been shown to be regulated by various nutrients and nutritional stresses. Given the high prevalence of mtDNA mutations in humans and their impact on mitochondrial function, it is important to investigate the mechanisms that regulate mtDNA mutation. Here, we discuss mitochondrial genetics and mtDNA mutations and their implications for human diseases. We also examine the role of mitophagy as a therapeutic target, highlighting how nutrients may eliminate mtDNA mutations through mitophagy.

Influence of diet and manure management on ammonia and greenhouse gas emissions from dairy barns

Dairy systems are a source of pollutant emissions, such as greenhouse gases (GHG) and NH3 that are associated with impacts on the environment. Gas emissions in barns are related mainly to diet intake and chemical composition, N excretion and manure management. A reduction in dietary N is known to be an effective way to reduce N excretion and the resulting NH3 emissions. However, most studies consider manure in liquid form with frequent removal from the barn. In deep litter systems, several processes can occur during the accumulation of solid manure that result in variable gas emissions. The objective of this experiment was to investigate the influence of the interaction between dietary CP (low or high) and manure management (liquid or solid) on gas emissions (NH3, N2O, CH4) at the barn level. Dietary treatments provided either low (LowN; 12% CP) or high (HighN; 18% CP) degradable protein to modify the amount of total ammonia nitrogen (TAN) excreted. The cows were housed for two 8-week periods in two mechanically ventilated rooms equipped to manage manure either in liquid (LM; slurry) or solid form (SM; deep litter). In the LM treatment, N balance was measured for 4 days. As expected, animals fed the LowN diet ingested 35% less N and excreted 65% less N in their urine, with no reduction in faecal N excretion and N secretion in milk. On the LowN diet, excretion of urea-N and NH3-N emissions were reduced regardless of the manure management. On the HighN diet, urinary urea-N excretion was three times as high, while NH3-N emissions were 3.0 and 4.5 times as high in LM and SM, respectively. Manure management strongly influenced CH4-C emissions, which were 30% higher in SM than in LM, due to the accumulation of litter. Moreover, gas emissions from solid manure increased over the accumulation period, except for NH3 on the LowN diet. Finally, our results suggest that methods used for national inventories would become more accurate by considering the variability in TAN excretion, which is the primary factor that influences NH3 emissions.

Validation of mobile in situ measurements of dairy husbandry emissions by fusion of airborne/surface remote sensing with seasonal context from the Chino Dairy Complex

Mobile in situ concentration and meteorology data were collected for the Chino Dairy Complex in the Los Angeles Basin by AMOG (AutoMObile trace Gas) Surveyor on 25 June 2015 to characterize husbandry emissions in the near and far field in convoy mode with MISTIR (Mobile Infrared Sensor for Tactical Incident Response), a mobile upwards-looking, column remote sensing spectrometer. MISTIR reference flux validated AMOG plume inversions at different information levels including multiple gases, GoogleEarth imagery, and airborne trace gas remote sensing data. Long-term (9-yr.) Infrared Atmospheric Sounding Interferometer satellite data provided spatial and trace gas temporal context. For the Chino dairies, MISTIR-AMOG ammonia (NH₃) agreement was within 5% (15.7 versus 14.9 Gg yr^-1, respectively) using all information. Methane (CH₄) emissions were 30 Gg yr^-1 for a 45,200 herd size, indicating that Chino emission factors are greater than previously reported. Single dairy inversions were much less successful. AMOG-MISTIR agreement was 57% due to wind heterogeneity from downwind structures in these near-field measurements and emissions unsteadiness. AMOG CH₄, NH₃, and CO₂ emissions were 91, 209, and 8200 Mg yr^-1, implying 2480, 1870, and 1720 head using published emission factors. Plumes fingerprinting identified likely sources including manure storage, cowsheds, and a structure with likely natural gas combustion. NH₃ downwind of Chino showed a seasonal variation of a factor of ten, three times larger than literature suggests. Chino husbandry practices and trends in herd size and production were reviewed and unlikely to add seasonality. Higher emission seasonality was proposed as legacy soil emissions, the results of a century of husbandry, supported by airborne remote sensing data showing widespread emissions from neighborhoods that were dairies 15 years prior, and AMOG and MISTIR observations. Seasonal variations provide insights into the implications of global climate change and must be considered when comparing surveys from different seasons.

Personal exposure of dairy workers to dust, endotoxin, muramic acid, ergosterol, and ammonia on large-scale dairies in the high plains Western United States

Dairy workers experience a high degree of bioaerosol exposure, composed of an array of biological and chemical constituents, which have been tied to adverse health effects. A better understanding of the variation in the magnitude and composition of exposures by task is needed to inform worker protection strategies. To characterize the levels and types of exposures, 115 dairy workers grouped into three task categories on nine farms in the high plains Western United States underwent personal monitoring for inhalable dust, endotoxin, 3-hydroxy fatty acids (3-OHFA), muramic acid, ergosterol, and ammonia through one work shift. Eighty-nine percent of dairy workers were exposed to endotoxin at concentrations exceeding the recommended exposure guidelines (adjusted for a long work shift). The proportion of workers with exposures exceeding recommended guidelines was lower for inhalable dust (12%), and ammonia (1%). Ergosterol exposures were only measurable on 28% of samples, primarily among medical workers and feed handlers. Milking parlor workers were exposed to significantly higher inhalable dust, endotoxin, 3-OHFA, ammonia, and muramic acid concentrations compared to workers performing other tasks. Development of large modern dairies has successfully made progress in reducing worker exposures and lung disease prevalence. However, exposure to endotoxin, dust, and ammonia continues to present a significant risk to worker health on North American dairies, especially for workers in milking parlors. This study was among the first to concurrently evaluate occupational exposure to assayable endotoxin (lipid A), 3-hydroxy fatty acids or 3-OHFA (a chemical measure of cell bound and noncell-bound endotoxins), muramic acid, ergosterol, and ammonia among workers on Western U.S. dairies. There remains a need for cost-effective, culturally acceptable intervention strategies integrated in OHS Risk Management and production systems to further optimize worker health and farm productivity.

Grazing intensity affects the environmental impact of dairy systems

Dairy products are major components of the human diet but are also important contributors to global environmental impacts. This study evaluated greenhouse gas (GHG) emissions, net energy intensity (NEI), and land use of confined dairy systems with increasing levels of pasture in the diet. A Wisconsin farm was modeled to represent practices adopted by dairy operations in a humid continental climate typical in the Great Lakes region and other climates that have large differences in seasonal temperatures. Five grazing scenarios (all of which contained some portion of confinement) were modeled based on different concentrations of dry matter intake from pasture and feed supplementation from corn grain, corn silage, and soybean meal. Scenarios that incorporate grazing consisted of 5 mo of pasture feeding from May to September and 7 mo of confined feeding from October to April. Environmental impacts were compared within the 5 scenarios that incorporate grazing and across 2 entirely confined scenarios with and without on-farm electricity production through anaerobic digestion (AD). To conduct a fair comparison, all scenarios were evaluated based on the same total amount of milk produced per day where resource inputs were adjusted according to the characteristics of each scenario. A cradle-to-farm gate life cycle assessment evaluated the environmental burdens that were partitioned by allocation between milk and meat and by system expansion when biogas-based electricity was produced. Overall, results for all scenarios were comparable. Enteric methane was the greatest contributor to GHG emissions, and the production of crops was the most energy-intense process. For the confined scenario without AD, GHG emissions were 0.87 kg of CO₂ equivalents, NEI was 1.59 MJ, and land use was 1.59 m²/kg of fat- and protein-corrected milk (FPCM). Anaerobic digestion significantly reduced emissions to 0.28 kg of CO₂ equivalents/kg of FPCM and reduced NEI to -1.26 MJ/kg of FPCM, indicating a net energy producing system and highlighting the potential of AD to improve the sustainability of confined systems. For scenarios that combined confinement and grazing, GHG emissions ranged from 0.84 to 0.92 kg of CO₂ equivalents, NEI ranged from 1.42 to 1.59 MJ, and land use ranged from 1.19 to 1.26 m²/kg of FPCM. All environmental impacts were minimized in scenarios that supplemented enough feed to increase milk yield but maintained dry matter intake from pasture at a level high enough to reduce material and energy use.

Carbon footprint of conventional and organic beef production systems: An Italian case study

Beef cattle production is a widespread activity in Italy in the agricultural field and determines an important impact on environment and resources consumption. Carbon footprint evaluation is thus necessary to evaluate the contributions of the different stages and the possible improvements of the production chain. In this study, two typical Italian beef production systems, a conventional and an organic one are investigated in order to evaluate the greenhouse gas emissions from "cradle to gate farm" by a Life Cycle Assessment (LCA) approach; the carbon footprint (CF) per 1kg of live weight meat is calculated. The contributions from feed production, enteric fermentation, and manure management are taken into account, in order to compare the life cycle of the two productions; also the carbon balance in soil is evaluated, in order to verify the impact in a life cycle perspective. The results of CF calculation of the two farms show that organic system (24.62kgCO_2eq/kg live weight) produce more GHG emissions than the conventional one (18.21kgCO_2eq/kg live weight) and that the enteric fermentation is the more heavy contribution, with a range of 50-54% of the global CF value. Improvements of the production chain could be realized by accurate feeding strategies, in order to obtain reduction of methane emissions from enteric digestion of cattles.

Nutritional and Environmental Effects on Ammonia Emissions from Dairy Cattle Housing: A Meta-Analysis

Nitrogen excreted in dairy manure can be potentially transformed and emitted as NH, which can create livestock and human respiratory problems and be an indirect source of NO. The objectives of this study were to: (i) investigate environmental factors influencing NH emissions from dairy housing; and (ii) identify key explanatory variables in the NH emissions prediction from dairy housing using a meta-analytical approach. Data from 25 studies were used for the preliminary analysis, and data from 10 studies reporting 87 treatment means were used for the meta-analysis. Season and flooring type significantly affected NH emissions. For nutritional effect analysis, the between-study variability (heterogeneity) of mean NH emission was estimated using random-effect models and had a significant effect ( < 0.01). Therefore, random-effect models were extended to mixed-effect models to explain heterogeneity regarding the available dietary and animal variables. The final mixed-effect model included milk yield, dietary crude protein, and dry matter intake separately, explaining 45.5% of NH emissions heterogeneity. A unit increase in milk yield (kg d) resulted in a 4.9 g cow d reduction in NH emissions, and a unit increase in dietary crude protein content (%) and dry matter intake (kg d) resulted in 10.2 and 16.3 g cow d increases in NH emissions, respectively, in the scope of this study. These results can be further used to help identify mitigation strategies to reduce NH emissions from dairy housing by developing predictive models that could determine variables with strong association with NH emissions.

Measures of nitrogen use efficiency and nitrogen loss from dairy production systems

In dairy production systems, tradeoffs can occur between fertilizer N applications and crop N use, feed N consumption and manure N excretion, and environmental impacts. This paper examines (i) how stocking rates affect N imports and management on dairy farms, N use efficiency (NUE; i.e., the amount of applied N incorporated into product N), and N loss; (ii) how reductions in fertilizer N and feed N may affect crop and milk production, NUE, and N loss; and (iii) why tradeoffs in N use outcomes should be considered when attempting to enhance overall NUE and reduce N loss. The Integrated Farm Simulation Model simulations of two representative dairy farm types and analyses of regional studies, long-term field experiments, and cow nutrition trials were used to demonstrate that (i) stocking rate affects cropping patterns, fertilizer and feed imports, and N loss; (ii) although fertilizer N reductions of 20 kg N ha may reduce slightly the crude protein (CP) content of corn silage (which would require purchase of additional CP supplements), this practice should not affect long-term corn yield but would reduce nitrate (NO) and nitrous oxide (NO) losses by 13 to 38%; (iii) dietary CP could be reduced on many dairy farms, which would not affect milk production but would reduce ammonia (NH) and NO emissions by 15 to 43%; and (iv) greater recognition of the tradeoffs in N use and N loss are needed to provide a better understanding of the potentials to enhance overall NUE and reduce environmental N loss from dairy production systems.

Ammonia emission model for whole farm evaluation of dairy production systems

Ammonia (NH) emissions vary considerably among farms as influenced by climate and management. Because emission measurement is difficult and expensive, process-based models provide an alternative for estimating whole farm emissions. A model that simulates the processes of NH formation, speciation, aqueous-gas partitioning, and mass transfer was developed and incorporated in a whole farm simulation model (the Integrated Farm System Model). Farm sources included manure on the floor of the housing facility, manure in storage (if used), field-applied manure, and deposits on pasture (if grazing is used). In a comprehensive evaluation of the model, simulated daily, seasonal, and annual emissions compared well with data measured over 2 yr for five free stall barns and two manure storages on dairy farms in the eastern United States. In a further comparison with published data, simulated and measured barn emissions were similar over differing barn designs, protein feeding levels, and seasons of the year. Simulated emissions from manure storage were also highly correlated with published emission data across locations, seasons, and different storage covers. For field applied manure, the range in simulated annual emissions normally bounded reported mean values for different manure dry matter contents and application methods. Emissions from pastures measured in northern Europe across seasons and fertilization levels were also represented well by the model. After this evaluation, simulations of a representative dairy farm in Pennsylvania illustrated the effects of animal housing and manure management on whole farm emissions and their interactions with greenhouse gas emissions, nitrate leaching, production costs, and farm profitability.

Potential use of milk urea nitrogen to abate atmospheric nitrogen emissions from wisconsin dairy farms

Urinary urea N (UUN) is the principal nitrogen (N) source controlling emissions of ammonia (NH) and nitrous oxide (NO) from dairy manure. The objectives of this study were (i) to study the integrative nature of dietary crude protein (CP) management, secretion of milk urea N (MUN), excretion of UUN, and N emissions from dairy production systems; (ii) to evaluate how associative changes in dietary CP, MUN, and UUN affect atmospheric N emissions from dairy farms; and (iii) to discuss some of the challenges and opportunities to an expanded use of MUN to enhance dietary CP use and decrease UUN excretion and N emissions from dairy farms. Milk urea N records of 37,889 cows in 197 herds in Wisconsin revealed that approximately one half of tested cows were likely consuming dietary CP in excess of requirement. Farm simulations were used to quantify the effect of dietary CP on whole-farm N emissions. At a statewide average MUN of 12.5 mg dL, 48 to 87% of UUN was emitted as NH, with the lowest loss from pasture-based farms and the greatest loss from tie-stall farms. Each 1 mg dL decrease of MUN (range, 16-10 mg dL) provided an associated daily decrease in UUN of 16.6 g per cow, which decreased NH and NO emissions from manure by 7 to 12%. Although more site-specific information is required on herd MUN-UUN relationships and more a reliable interpretation of MUN assay results is needed, monitoring of MUN may be used to enhance dietary CP use and to reduce UUN excretion and N emissions from Wisconsin dairy farms.

Gas emissions from dairy cows fed typical diets of Midwest, South, and West regions of the United States

Gas emissions were determined for dairy cows fed three diets formulated to represent feed ingredients typical of the Midwest, South, or West regions of the United States. Dairy cows were housed and monitored in 12 environmentally controlled rooms (4 cows diet). Two experiments were performed, representing two lactation stages (initial days in milk were 115 ± 39 d in Stage 1 and 216 ± 48 d in Stage 2). The results demonstrated that the combination of different dietary ingredients resulted in different gas emissions while maintaining similar dry matter intake (DMI) and milk yield (MY). Diet effect on ammonia (NH) emissions was more prominent in Stage 1. During Stage 1, cows fed the Midwest diet had the highest daily NH emission, corresponding to the highest crude protein (CP) concentration among the three regions. The differences in NH emissions (39.0%) were much larger than the percent difference in CP concentrations between diets (6.8%). Differences in N intake, N excretion, or milk urea N alone may not serve as a strong indicator of the potential to reduce NH emissions. Lower emissions of methane (CH) per unit DMI or per unit MY were observed for cows offered the South diet during Stage 1 as compared with that from cows offered the Midwest or West diets. No diet effect was observed for hydrogen sulfide (HS) emission per unit S intake, nor for nitrous oxide (NO) emission. The measured NH and CH emissions were comparable, but the NO emissions were much higher than those reported for tie-stall dairy barns in the literature.

Short communication: Evaluation of milk urea nitrogen as a management tool to reduce ammonia emissions from dairy farms

The purpose of this study was to compile and evaluate relationships between feed nitrogen (N) intake, milk urea N (MUN), urinary urea N (UUN), and ammonia (NH(3)) emissions from dairy farms to aid policy development. Regression relationships between MUN, UUN, and NH(3) emissions were compiled from studies conducted in Wisconsin, California, and the Netherlands. Relative reductions in NH(3) emissions were calculated as percentage decreases in NH(3) emissions associated with a baseline MUN level of 14 mg/dL (prevailing industry average). For 3 studies with cows in stanchion barns, relative NH(3) emission reductions of 10.3 to 28.2% were obtained when MUN declined from 14 to 10mg/dL. Similarly, analyses of 2 freestall studies provided relative NH(3) emission reductions of 10.5 to 33.7% when MUN levels declined from 14 to 10mg/dL. The relative reductions in NH(3) emissions from both stanchion and freestall barns can be associated directly with reductions in UUN excretion, which can be determined using MUN. The results of this study may help create new awareness, and perhaps eventual industry-based incentives, for management practices that enhance feed N use efficiency and reduce MUN, UUN, and NH(3) emissions from dairy farms.

Dietary crude protein and tannin impact dairy manure chemistry and ammonia emissions from incubated soils

Excess crude protein (CP) in dairy cow diets is excreted mostly as urea nitrogen (N), which increases ammonia (NH) emissions from dairy farms and heightens human health and environmental concerns. Feeding less CP and more tannin to dairy cows may enhance feed N use and milk production, abate NH emissions, and conserve the fertilizer N value of manure. Lab-scale ventilated chambers were used to evaluate the impacts of CP and tannin feeding on slurry chemistry, NH emissions, and soil inorganic N levels after slurry application to a sandy loam soil and a silt loam soil. Slurry from lactating Holstein dairy cows (Bos taurus) fed two levels of dietary CP (low CP [LCP], 155 g kg; high CP [HCP], 168 g kg) each fed at four levels of dietary tannin extract, a mixture from red quebracho (Schinopsis lorentzii) and chestnut (Castanea sativa) trees (0 tannin [0T]; low tannin [LT], 4.5 g kg; medium tannin [MT], 9.0 g kg; and high tannin [HT], 18.0 g kg) were applied to soil-containing lab-scale chambers, and NH emissions were measured 1, 3, 6, 12, 24, 36, and 48 h after slurry application. Emissions from the HCP slurry were 1.53 to 2.57 times greater ( < 0.05) than from the LCP slurry. At trial's end (48 h), concentrations of inorganic N in soils were greater ( < 0.05) in HCP slurry-amended soils than in LCP slurry-amended soils. Emissions from HT slurry were 28 to 49% lower ( < 0.05) than emissions from 0T slurry, yet these differences did not affect soil inorganic N levels. Emissions from the sandy loam soil were 1.07 to 1.15 times greater ( < 0.05) than from silt loam soil, a result that decreased soil inorganic N in the sandy loam compared with the silt loam soil. Larger-scale and longer-term field trails are needed to ascertain the effectiveness of feeding tannin extracts to dairy cows in abating NH loss from land-applied slurry and the impact of tannin-containing slurry on soil N cycles.

Ecoregion and farm size differences in dairy feed and manure nitrogen management: A survey

Sheppard, S. C., Bittman, S., Swift, M. L., Beaulieu, M. and Sheppard, M. I. 2011. Ecoregion and farm size differences in dairy feed and manure nitrogen management: A survey. Can. J. Anim. Sci. 91: 459–473. This paper describes the activity of dairy farmers in Canada in 2005 related to the use of nitrogen (N) and especially practices that led to loss of ammonia (NH3). The data were obtained from a large-scale, statistically structured survey conducted across Canada. The survey sampling was stratified into 10 Ecoregions and across farm size. Numbers of lactating cows per farm were nearly twofold more in the west than the east. In western Canada less than 31% of barns were “tie-stall” type whereas 80% were tie-stall in the St. Lawrence Lowlands. The numbers of hours lactating cows spent in barns, standing yards, exercise fields and pasture varied with Ecoregion and farm size, important data in relation to NH3 emissions. Pasturing was more common in the east than west. Matching feed crude protein concentrations to physiological needs seems a potential best management practice, and smaller farms with tie-stalls seemed more prone to adjusting feed to individual cows compared with large farms with loose housing. Manure handling was divided, with slurry prominent especially in the west. Manure spreading practices also varied by Ecoregion. Overall, it is clear that national averages do not well represent dairy farm management: Ecoregion and farm size differences are significant.

Tannin extracts abate ammonia emissions from simulated dairy barn floors

Feeding more tannin and less crude protein (CP) to dairy cows may have synergistic impacts on reducing NH emissions from dairy barns. Three trials using lab-scale ventilated chambers with concrete floors were conducted to determine the impacts on NH emission of tannin and CP feeding, tannin feeding on urease activity in feces, and tannin application directly to the barn floor. For Trial 1, mixtures of feces and urine from lactating Holstein dairy cows () fed four levels (g kg) of dietary tannin extract [a mixture from red quebracho () and chestnut () trees]: 0 tannin (0T), 4.5 (low tannin [LT]), 9.0 (medium tannin [MT]), and 18.0 (high tannin [HT]); each fed at two levels (g kg) of dietary CP: 155 low CP (LCP) and 168 high CP (HCP) were applied to chambers. For Trial 2, urea solution was added to feces obtained from cows fed 0T, MT, and HT at HCP. For Trial 3, tannin amounts equivalent to those fed at 0T, MT, and HT were applied directly to feces-urine mixtures from 0T-HCP. For all trials, NH emissions were measured 1, 3, 6, 12, 24, 36, and 48 h after treatment application. For Trial 1, reductions in NH emission due to tannin feeding were greatest when fed at LCP: The LCP-LT and LCP-HT treatments emitted 30.6% less NH than LCP-0T, and the HCP-LT and HCP-HT treatments emitted 16.3% less NH than HCP-0T. For Trial 2, feeding tannin decreased urease activity in feces, resulting in an 11.5% reduction in cumulative NH loss. For Trial 3, the application of tannin directly to simulated barn floors also apparently decreased urease activity, resulting in an average reduction in cumulative NH emissions of 19.0%. Larger-scale trails are required to ascertain the effectiveness of tannin extracts in abating NH loss from dairy barn floors.

Review: Ammonia emissions from dairy farms and beef feedlots

Hristov, A. N., Hanigan, M., Cole, A., Todd, R., McAllister T. A., Ndegwa, P. and Rotz, A. 2011. Review: Ammonia emissions from dairy farms and beef feedlots. Can. J. Anim. Sci. 91: 1–35. Ammonia emitted from animal feeding operations is an environmental and human health hazard, contributing to eutrophication of surface waters and nitrate contamination of ground waters, soil acidity, and fine particulate matter formation. It may also contribute to global warming through nitrous oxide formation. Along with these societal concerns, ammonia emission is a net loss of manure fertilizer value to the producer. A significant portion of cattle manure nitrogen, primarily from urinary urea, is converted to ammonium and eventually lost to the atmosphere as ammonia. Determining ammonia emissions from cattle operations is complicated by the multifaceted nature of the factors regulating ammonia volatilization, such as manure management, ambient temperature, wind speed, and manure composition and pH. Approaches to quantify ammonia emissions include micrometeorological methods, mass balance accounting and enclosures. Each method has its advantages, disadvantages and appropriate application. It is also of interest to determine the ammonia emitting potential of manure (AEP) independent of environmental factors. The ratio of nitrogen to non-volatile minerals (phosphorus, potassium, ash) or nitrogen isotopes ratio in manure has been suggested as a useful indicator of AEP. Existing data on ammonia emission factors and flux rates are extremely variable. For dairy farms, emission factors from 0.82 to 250 g ammonia per cow per day have been reported, with an average of 59 g per cow per day (n=31). Ammonia flux rates for dairy farms averaged 1.03 g m−2 h−1 (n=24). Ammonia losses are significantly greater from beef feedlots, where emission factors average 119 g per animal per day (n=9) with values as high as 280 g per animal per day. Ammonia flux rate for beef feedlots averaged 0.174 g m−2 h−1 (n=12). Using nitrogen mass balance approaches, daily ammonia nitrogen losses of 25 to 50% of the nitrogen excreted in manure have been estimated for dairy cows and feedlot cattle. Practices to mitigate ammonia emissions include reducing excreted N (particularly urinary N), acidifying ammonia sources, or binding ammonium to a substrate. Reducing crude protein concentration in cattle diets and ruminal protein degradability are powerful tools for reducing N excretion, AEP, and whole-farm ammonia emissions. Reducing dietary protein can also benefit the producer by reducing feed cost. These interventions, however, have to be balanced with the risk of lost production. Manure treatment techniques that reduce volatile N species (e.g., urease inhibition, pH reduction, nitrification-denitrification) are also effective for mitigating ammonia emissions. Another option for reducing ammonia emissions is capture and treatment of released ammonia. Examples in the latter category include biofilters, permeable and impermeable covers, and manure incorporation into the soil for crop or pasture production. Process-level simulation of ammonia formation and emission provides a useful tool for estimating emissions over a wide range of production practices and evaluating the potential benefits of mitigation strategies. Reducing ammonia emissions from dairy and beef cattle operations is critical to achieving environmentally sustainable animal production that will benefit producers and society at large.

Prediction of ammonia emission from dairy cattle manure based on milk urea nitrogen: relation of milk urea nitrogen to ammonia emissions

The main objectives of this study were to assess the relationship between ammonia emissions from dairy cattle manure and milk urea N (MUN; mg/dL) and to test whether the relationship was affected by stage of lactation and the dietary crude protein (CP) concentration. Twelve lactating multiparous Holstein cows were randomly selected and blocked into 3 groups of 4 cows intended to represent early [123+/-26 d in milk (DIM)], mid (175+/-3 DIM), and late (221+/-12 DIM) lactation stages. Cows within each stage of lactation were randomly assigned to a treatment sequence within a split-plot Latin square design balanced for carryover effects. Stage of lactation formed the main plots (squares) and dietary CP levels (15, 17, 19, and 21% of diet dry matter) formed the subplots. The experimental periods lasted 7 d, with d 1 to 6 used for adjustment to diets and d 7 used for total collection of feces and urine as well as milk sample collection. The feces and urine from each cow were mixed in the proportions in which they were excreted to make slurry that was used to measure ammonia emissions at 22.5 degrees C over 24 h using flux chambers. Samples of manure slurry were taken before and after ammonia emission measurements. The amount of slurry increased by 22% as dietary CP concentration increased from 15 to 21%, largely because of a greater urine volume (25.3 to 37.1 kg/d). Initial urea N concentration increased linearly with dietary CP from 153.5 to 465.2 mg/dL in manure slurries from cows fed 15 to 21% CP diets. Despite the large initial differences, the final concentration of urea N in manure slurries was less than 10.86 mg/dL for all dietary treatments. The final total ammoniacal N concentration in manure slurries increased linearly from 228.2 to 508.7 mg/dL as dietary CP content increased from 15 to 21%. Ammonia emissions from manure slurries ranged between 57 and 149 g of N/d per cow and increased linearly with dietary CP content, but were unaffected by stage of lactation. Ammonia emission expressed as a proportion of N intake increased with percentage CP in the diet from about 12 to 20%, whereas ammonia emission as a proportion of urinary urea N excretion decreased from 67 to 47%. There was a strong relationship between ammonia emission and MUN [ammonia emission (g/d per cow)=25.0 (+/-6.72)+5.03 (+/-0.373) x MUN (mg/dL); R(2)=0.85], which was not different among lactation stages. Milk urea N concentration is one of several factors that allows prediction of ammonia emissions from dairy cattle manure.

The effects of ruminally degraded protein on rumen fermentation and ammonia losses from manure in dairy cows

This experiment investigated the effect of dietary crude protein (CP) and ruminally degraded protein (RDP) levels on rumen fermentation, digestibility, ammonia emission from manure, and performance of lactating dairy cows. The experiment was a replicated 3 x 3 Latin square design with 6 cows. Three diets varying in CP concentration were tested (CP, % of dry matter): 15.4 (high CP, control), 13.4 (medium CP), and 12.9% (low CP). These diets provided metabolizable protein balances of 323, -44, and 40 g/d and RDP balances of 162, -326, and -636 g/d (high, medium, and low, respectively). Both the medium and low CP diets decreased ruminal pH compared with high CP, most likely because of the higher nonfiber carbohydrate concentration in the former diets. Ruminal ammonia pool size (rumen ammonia N was labeled with (15)N) and the concentration of total free amino acids were greater for the high CP diet than for the RDP-deficient diets. Apparent total-tract nutrient digestibilities were not affected by treatment. Both the medium and low CP diets resulted in lower absolute and relative excretion of urinary N compared with the high CP diet, as a proportion of N intake. Excretion of fecal N and milk yield and composition were not affected by diet. Milk N efficiency (milk N / N intake) and the cumulative secretion of ammonia-(15)N in milk protein were greater for the RDP-deficient diets, and milk urea N concentration was greater for the high CP diet. Both medium and low CP diets decreased the irreversible loss of ruminal ammonia N compared with the high CP diet. The rate and cumulative ammonia emissions from manure were lower for the medium and low CP diets compared with the high CP diet. Overall, this study demonstrated that dairy diets with reduced CP and RDP concentrations will produce manure with lower ammonia-emitting potential without affecting cow performance, if metabolizable protein requirements are met.

Nitrogen losses from dairy manure estimated through nitrogen mass balance and chemical markers

Ammonia is an important air and water pollutant, but the spatial variation in its concentrations presents technical difficulties in accurate determination of ammonia emissions from animal feeding operations. The objectives of this study were to investigate the relationship between ammonia volatilization and delta15N of dairy manure and the feasibility of estimating ammonia losses from a dairy facility using chemical markers. In Exp. 1, the N/P ratio in manure decreased by 30% in 14 d as cumulative ammonia losses increased exponentially. Delta 15N of manure increased throughout the course of the experiment and delta15N of emitted ammonia increased (p<0.001) quadratically from -31 per thousand to -15 per thousand. The relationship between cumulative ammonia losses and delta15N of manure was highly significant (p<0.001; r2=0.76). In Exp. 2, using a mass balance approach, approximately half of the N excreted by dairy cows (Bos taurus) could not be accounted for in 24 h. Using N/P and N/K ratios in fresh and 24-h manure, an estimated 0.55 and 0.34 (respectively) of the N excreted with feces and urine could not be accounted for. This study demonstrated that chemical markers (P, K) can be successfully used to estimate ammonia losses from cattle manure. The relationship between manure delta15N and cumulative ammonia loss may also be useful for estimating ammonia losses. Although promising, the latter approach needs to be further studied and verified in various experimental conditions and in the field.

Effects of reducing dietary nitrogen on ammonia emissions from manure on the floor of a naturally ventilated free stall dairy barn at low (0-20 degrees C) temperatures

This study was conducted to determine the potential for reducing ammonia (NH3) emissions from manure deposited on the floor of a naturally ventilated free stall barn by mid-lactation dairy cows fed reduced or normal N diets. Two crude protein (CP) diets (178 g kg(-1) [high] and 159 g kg(-1) [low] dry matter ), were used. The diets were fed to 48 Holstein cows in a replicated crossover design with two pens per diet. The NH3 emitted from the manure deposited on the floor was measured using a dynamic flux chamber. The NH3 emissions were 2.7 (+/-2.0) and 2.9 (+/-1.8) g N cow(-1) d(-1) for high and low CP diets, respectively. Ammonia emission rates were significantly affected by manure pH, TKN, and ambient air temperature (P<0.05). Dietary CP affected the feed N intake (8.7 and 7.1 kg pen(-1) d(-1) for high and low CP, respectively), but did not affect milk yield (500 and 489 kg pen(-1) d(-1) for high and low CP, respectively) and milk CP content (30 g kg(-1) for both the high and low CP diets). The N utilization efficiency was 29.0% and 32.7% for the high and low CP diets, respectively. Reducing dietary CP reduced total Kjeldahl N (TKN) in manure, but did not affect the total ammoniacal N (TAN) in manure and had no significant effect on the ammonia emission rates from the barn floor.

Effects of dried distillers' grains with solubles (wheat-based) in feedlot cattle diets on feces and manure composition

The use of dried distillers' grains with solubles (DDGS) in feedlot cattle (Bos taurus) diets is increasing as the bio-ethanol industry expands. This study investigated how wheat (Triticum aestivum L.) DDGS-based diets impact feedlot cattle nutrient and volatile fatty acid (VFA) excretion. Feedlot heifers were fed DDGS at 0 (Control) 20, 40, 60% or 60% + Ca (1% limestone) of dietary dry matter. Feces and manure were sampled monthly over a 133-d finishing period. Total nitrogen (TN) (feces only), total phosphorus (TP), pH (manure only), and water soluble NH(4)(+) and P contents in feces and manure were higher with 40 and 60% DDGS diets than with the Control. Significant increases in isobutyric, valeric, and isovaleric VFAs (by far the most odorous in manure) were also observed in the feces with 40 and 60% DDGS diets, although there was no change in the total VFA content with diet. Wheat DDGS manure, with higher N and P contents, should be beneficial to crop production. However, it could potentially increase N and P loading on crop lands after application and contribute to greater NH(3) emission and malodor intensity while manure is in the feedlot pen. Estimated manure N loss while in feedlot pens also increased significantly with dietary DDGS levels. The small (nonsignificant) differences in total and soluble N and P in feces and manure between 20% DDGS and the Control (0% wheat DDGS) suggest that excess nutrient flow to the environment and malodors can be controlled by restricting wheat DDGS to a maximum of 20% in cattle diets.