Location: Livestock Nutrient Management Research2013 Annual Report
1a. Objectives (from AD-416):
Long-term goals are to: 1) provide nutritional and management strategies for use by cattle producers to decrease potential adverse effects of feeding operations on the environment without adversely affecting animal performance, 2) quantify and minimize gaseous emissions from feedyards and dairies that may adversely affect the environment, and 3) produce on-farm energy that increases the value of manure and reduces dependence on fossil fuel. We seek to provide science-based information and technologies that can be used by livestock producers, extension specialists, and regulators to best manage feedyard and dairy manure to protect air quality, maintain or improve production efficiency, and improve sustainability of livestock production systems. Over the next 5 years we will focus on: Obj. 1. Develop feeding strategies that optimize utilization of energy, nitrogen, and phosphorus contained in beef cattle diets formulated with and without byproducts such as distiller's grain, in order to minimize excretion in manure. 1A. Measure effects of finishing diet composition on nitrogen and phosphorus excretion, nitrogen volatilization losses, and manure composition of finishing beef cattle in feeding trials. 1B. Measure effects of finishing diet composition on energy excretion, enteric methane losses, and energy metabolism of finishing beef cattle using respiration ca1orimetry. 1C. Determine relative degradable intake protein (DIP)/non-protein-nitrogen (NPN) value of distiller's solubles compared to urea. Obj. 2. Develop methods to quantify, and management strategies to minimize, the generation of greenhouse gases and other atmospheric emissions from feedyards and dairies. 2A. Monitor emissions of ammonia and greenhouse gases from beef cattle feedyards and dairies in the southern Great Plains. 2B. Quantify physical and chemical processes controlling and regulating ammonia and greenhouse gas emissions from feedyard and dairy pen surfaces, retention ponds, lagoons. 2C. Identify, verify, validate process-based models of ammonia and greenhouse gas emissions for beef cattle feedyards and dairies. 2D. Determine effects of pen surface amendments on ammonia emissions from feedyard and dairy pen surfaces, retention ponds, lagoons. 2E. Determine methane production potential of manure from cattle fed steam-flaked corn and distiller's grains based diets. Obj. 3. Isolate, identify, and characterize microbial strains and consortia that are capable of efficiently producing hydrogen and/or electricity from feedyard manures while also reducing pathogen loads. 3A. Identify microorganisms that are electricigens or microbial consortia that can act as electricigens that are present in either beef or dairy confined animal feeding operations. 3B. Determine potential power output of identified electricigens-microbial consortia in low- and high-power fuel cells using various types and forms of manure fuels. 3C. Evaluate microbial consortia-bioreactor designs for efficient generation of hydrogen from manure wastes. 3D. Evaluate influence of various methods of processing manure wastes for use as fuel sources on survival of zoonotic agents, antibiotic resistant gene complexes.
1b. Approach (from AD-416):
Experimental objectives are accomplished through a combination of cooperative,multidisciplinary studies that extend from basic laboratory-scale experiments to practical field experiments. Lab-scale and research feedlot-scale studies are used to determine how chemical, physical and dietary factors affect nutrient losses and atmospheric emissions and for initial evaluation of potential abatement measures. Larger field studies will be used to determine the atmospheric losses under practical conditions in the Southern Great Plains of the United States. Laboratory-scale studies will examine the feasibility of producing electricity with microbial fuel cells that use feedlot and/or dairy manures as sources of fuel and microbes.
3. Progress Report:
We completed a 10-year study that greatly expanded the understanding of ammonia and methane emissions from beef cattle feedyards, the factors that control emissions, and ways to estimate and predict emissions. These data were used to refine ammonia emission factors, the current paradigm for large-scale estimation of ammonia emissions. Emission factors used by U.S. Environmental Protection Agency and in some published reviews appear to be too low. For feedyards where cattle are fed diets containing optimum crude protein concentrations recommended by National Research Council guidelines, cattle lost approximately 16.8 kg of ammonia over a 150-day feeding period, which equated to an ammonia emission factor of 40 kg/animal/year. Because ammonia emissions are sensitive to diet, ambient temperature, and other factors, process-based models that calculate emissions using the actual physical, chemical, and biological processes that control emissions are a more realistic approach to quantify emissions than emission factors. Studies were conducted to test and modify empirical and process-based models of ammonia emission from feedyards. Ammonia emissions estimated using the process-based model Manure-DNDC agreed well with emissions measured at feedyards. Ammonia emissions are highly dependent upon urinary N excretion; therefore, a meta-analysis was used to develop empirical models to predict urinary and fecal nitrogen excretion by beef cattle as a function of dietary protein. These equations and models can be used to improve estimates of ammonia losses and to evaluate mitigation strategies. Emissions of methane, from a southern High Plains feedyard agreed with rates in the literature and with the Tier 2 emission factors currently used by the Intergovernmental Panel on Climate Change and the U.S. EPA. Our understanding of feedyard emissions has greatly expanded, but less is known about gaseous emissions from grazing beef cattle systems. Research was initiated to measure gaseous emissions from cattle grazing systems. An in vitro gas production system was used to evaluate effects of supplementation strategies on enteric methane production. Eddy covariance systems that measure methane and carbon dioxide fluxes were acquired and field tested. A remotely controlled methane and ammonia measuring system that integrates scanning open path lasers and GPS-tracked cattle is under development. A commercial system that measures enteric methane and total carbon dioxide production of individual cattle is currently being tested. Feeding steam-flaked corn decreased methane emissions and the quantity of manure collected from feedlot pens by 20 to 30% compared to feeding dry rolled corn-based diets. Feeding 20% (dry matter basis) wet distillers grains (WDG) increased total manure production by about 15% compared to feeding 0% WDG. Feeding 20% WDG did not affect N volatilization losses as a percentage of N intake, but because of greater N intake, increased total N volatilization losses (kg/head) by about 10%. Cattle fed steam-flaked corn-based diets had greater apparent N volatilization losses (as % of N intake) than heifers fed dry rolled corn-based diets.
1. Integrated research updates beef feedyard ammonia emission factors. Ammonia emissions from cattle feeding operations are currently estimated in national inventories using emission factors drawn from scientific literature. However, emission factors are usually specific to the conditions under which data were collected, and may or may not accurately represent actual emissions. Scientists at the USDA-ARS Conservation and Production Research Laboratory, Bushland, Texas, updated the state of emission factor science by integrating research conducted under the USDA-funded Federal Air Quality Initiative project "Air Quality: Reducing Emissions from Cattle Feedlots and Dairies (Texas and Kansas)", in a series of published papers, conference proceedings and presentations. For beef cattle feedyards where cattle are fed optimum crude protein diets recommended by National Research Council guidelines, ammonia emissions were approximately 16.8 kg per head during a 150-day feeding period, which equated to an ammonia emission factor of 40 kg/animal/year. Ammonia emissions are sensitive to diet crude protein and environmental temperature, which can be included in models to further refine ammonia emission factors. Adoption of this research-based ammonia emission factor approach can potentially improve the accuracy of national ammonia emission inventories and help guide better policy decisions.
2. Methane emissions from a beef cattle feedyard. Methane (CH4) is a potent greenhouse gas that contributes to global warming and climate change. Ruminants, especially cattle, are a significant source of CH4 to the atmosphere. Scientists from the USDA-ARS Conservation and Production Research Laboratory, Bushland, Texas, measured CH4 emissions at a commercial cattle feedyard during winter and summer of 2010. Methane loss as a fraction of the gross energy intake (called Ym), is an important parameter used by the Intergovernmental Panel on Climate Change (IPCC) to estimate greenhouse gas inventories. We found that Ym was 3.2% in summer, and was close to the 3.0% value used by IPCC. Data collected during the winter were higher, but results were considered less certain and biased high because of low animal occupancy and other factors that may have affected the accuracy of the method used. These data confirm that the IPCC Tier 2 approach to estimate enteric emissions from feedyard cattle is probably applicable to Southern High Plains feedyards and thus can be used to develop inventories of methane emissions.
3. Predicting ammonia emissions from beef cattle feedyards with process-based models. Ammonia loss from beef cattle feedyards results in manure with a lower fertilizer value, and it can also cause environmental pollution. Both process-based and mathematical models have been developed that estimate ammonia losses from different types of livestock production systems; however, it was unknown if these models could predict ammonia loss from beef cattle feedyards. Collaborative research between scientists at the ARS Conservation and Production Research Laboratory in Bushland, Texas, the University of New Hampshire, and Applied Geosolutions LLC in Durham, New Hampshire, was conducted to evaluate Manure-DNDC, a newly developed process-based biogeochemical model, by comparing model predictions to real ammonia loss measurements taken from two commercial feedyards in Texas. The model predictions agreed well with measurements from both feedyards, and the model was sensitive to air temperature and the amount of protein in the animal diet. This showed that Manure-DNDC was useful for quantifying feedyard ammonia emissions and could provide more accurate information to regulatory agencies. Manure-DNDC could also be used to test methods to reduce ammonia loss and evaluate how different feedyard management practices could influence farm nutrient balances.
4. Effects of grain processing on the carbon footprint of fed beef cattle. Most cattle fed in the southern Great Plains are fed diets based on steam-flaked corn. Steam flaking uses additional natural gas that is not required when cattle are fed diets based on dry-rolled corn. Using data from multiple trials conducted at their laboratory, researchers at the ARS Conservation and Production Research Laboratory in Bushland, Texas, calculated the effects of steam flaking on the carbon footprint of cattle fed high-concentrate finishing diets. Steam flaking required additional fossil fuel compared to dry rolling corn; however, cattle fed steam-flaked corn based diets produced less enteric methane, excreted less organic matter (which decreased manure methane production), and improved feed efficiency, thus decreasing the quantity of corn required for finishing. Overall, steam flaking decreased the carbon footprint of cattle feeding by 8 to 18% compared to feeding dry-rolled corn. These results can be important in developing accurate Life Cycle Analysis of cattle feeding and in improving sustainability of cattle production.
5. Estimating enteric methane production from feedlot cattle. The models currently available to estimate enteric methane emissions from cattle were developed using animals fed high-forage diets, and thus they tend to greatly overestimate emissions from cattle fed high-concentrate finishing diets. A scientist at the ARS Conservation and Production Research Laboratory in Bushland, Texas, developed a modified IPCC Tier 2 system to estimate enteric methane production from feedlot cattle based on their feed intake, dietary fat levels, grain processing method, and dietary grain concentration. This model appears to give more accurate values than exisitng models and equations and also allows producers to estimate dietary effects on feedyard emissions. This method is currently part of a "Tool" developed by the USDA-Office of Chief Economist for producers and regulators to use in estimating greenhouse gas emissions from agriculture.
Buttrey, E.K., Jenkins, K.H., Lewis, J.B., Smith, S.B., Miller, R.K., Lawrence, T.E., McColum, F.T., Pinedo, P.J., Cole, N.A., MacDonald, J.C. 2013. Effects of 35% corn wet distillers grains plus solubles in steam-flaked and dry-rolled corn-based finishing diets on animal performance, carcass characteristics, beef fatty acid composition, and sensory attributes. Journal of Animal Science. 91:1850-1865.