2012 Annual Report
1a.Objectives (from AD-416):
To determine, in cooperation with scientists from Texas AgriLife Research, Kansas State University (KS), Texas A&M University (TAMU), and West Texas A&M University (WTAMU), atmospheric ammonia and methane concentrations and emissions at commercial beef cattle feedyards, and to determine the effects of environmental and management factors on the emissions.
1b.Approach (from AD-416):
Ammonia emissions will be measured at several commercial beef cattle feedyards and dairies in Texas using open path lasers and a backward Lagrangian Stochastic model. Methane emissions will be measured from the retention pond and pen areas of feedyards using the same methodologies. Nitrogen and carbon balance will be determined based on chemical composition of diets, fresh feces, aged manure, and animal weight gain. Effects of environmental factors, pond chemistry, pen surface chemistry, and management factors on emissions will be monitored. A respiration calorimetry system will be used to measure enteric and metabolic methane, carbon dioxide, ammonia and hydrogen sulfide flux from cattle. These data have value for development, improvement, and/or verification for statistical and process-based models of ammonia and methane emissions. Potential methods to decrease ammonia emissions will be studied using lab-scale and small plot-scale studies. Ammonia emissions from pen surfaces treated with varying chemicals will be measured using flow through lab chambers or a static chember on feedlot plots.
Methane emissions from a commercial feedyard were estimated using open path laser spectroscopy and a dispersion model. Methane emission rates were in agreement with values in the literature, and showed that cattle fed high-concentrate diets tend to have lower methane emissions than cattle that consume forage-based diets. Compared with the measurement of ammonia emissions, methane monitoring presented several challenges that reduced the quantity of high-quality data, including limited acceptable wind directions and the requirement of an additional background measure of methane concentration. To improve estimates of methane emission from feedyards and dairies, new technologies and methods to measure greenhouse gas emissions are in development. Two eddy covariance systems that can directly measure methane and carbon dioxide were acquired, and one was deployed and tested at a typical short grass prairie site for six months. A motorized scanning mount for an open path methane laser was also acquired which allows automatic collection of average methane concentrations across multiple paths, rather than a single path. The scanning laser and eddy covariance systems will be deployed at a commercial beef cattle feedyard to measure whole-farm methane emissions in autumn of 2012 to augment measurements by collaborating scientists from Texas A&M AgriLife Research.
Accurate and user-friendly models to predict ammonia emissions from livestock operations are needed by policy makers, producers and consultants to accurately estimate ammonia emissions and to evaluate mitigation strategies. Scientists with the USDA-ARS Conservation and Production Research Laboratory in Bushland, TX, conducted studies to develop new models and to test and improve existing models of ammonia emissions. A comprehensive database of ammonia emissions from three commercial feedyards, collected over the past 8 years, was used to explore the relationships between ammonia emissions, environmental temperature, and the crude protein content of cattle finishing diets. Environmental temperature is a controlling factor for many chemical reactions involved in ammonia volatilization, and it strongly influenced average monthly ammonia emissions at feedyards. Dietary crude protein concentration was also a significant controlling factor. When crude protein intake exceeded the animal requirements, ammonia emissions increased rapidly. Equations to predict ammonia emission from beef cattle feedyards in the southern Great Plains were developed using environmental temperature and dietary crude protein concentration. These simple equations can be used by managers and/or consultants to improve estimates of ammonia loss from beef cattle feedyards.
Because the amount of ammonia emitted from beef cattle feedyards is highly dependent upon the quantity and form of nitrogen excreted by the animals, a meta-analysis was conducted using data from 13 published papers to determine the relationship between dietary nitrogen intake and urinary and fecal nitrogen excretion by beef cattle. Empirical models were developed to predict urinary and fecal nitrogen excretion by beef cattle as a function of daily nitrogen intake and the protein concentration in the animal diet. These equations may be useful in larger models to better estimate ammonia emissions from feedyards.
Two existing process-based models, Manure-DNDC and the Integrated Farm System Model (IFSM), were evaluated for their ability to predict ammonia emissions from beef cattle feedyards in the Southern High Plains. Ammonia emissions estimated using the models were compared with ammonia emissions measured from two commercial feedyards over two years. The predicted emissions made by both Manure-DNDC and IFSM agreed well with measured emissions, indicating that these models could be useful for assisting with ammonia emissions reporting for commercial feedyards, providing information for policy makers, and helping evaluate the effects of specific management practices and mitigation strategies on feedlot ammonia emissions and nutrient balances.
Dairies, a growing industry in the Southern High Plains, are sources of environmentally important gases such as methane and ammonia. Scientists at the ARS Conservation and Production Research Laboratory, Bushland, TX, teamed with researchers from Texas A&M AgriLife Research, West Texas A&M University, and New Mexico State University to conduct two intensive and comprehensive studies at a 3,500-cow open-lot dairy. The studies focused on emissions of methane, ammonia, odor and particulate matter during two intensive summer field campaigns in 2009 and 2010. Uncovered lagoons were a significant source of methane emissions, averaging 209 grams of methane per cow daily in 2009, and 359 g per cow daily in 2010. Thus, lagoons are a potential point to significantly decrease methane emissions from open-lot dairies. The daily pattern of methane emissions from the lagoons was affected by development of a bubble layer on the surface of the lagoons during the night. The loss of this layer at sunrise (due to increased winds and/or solar heating) often resulted in a sudden burst of methane emissions in the morning. Methane losses were greatest from the primary lagoons that directly received wastewater and manure solids from the dairy and was lower from secondary lagoons that received only overflow from the primary lagoons. Ammonia losses from dairy lagoons were low; averaging from 14 to 30 g per cow daily during the summer. That loss represented less than 5% of the nitrogen fed to cows at the dairy.
To better understand the key processes that control ammonia emissions from beef cattle feedyards, ammonium sorption by beef feedyard manure was quantified and characterized in a laboratory study. This research indicated that beef manure can sorb significant quantities of ammonium, and sorption is greater at lower temperatures. However, sorbed ammonium was easily removed by competing cations and ammonia was lost when manure was dried. This indicates that sorption is not likely to be an important long-term mechanism for reducing ammonium-ammonia dissociation and ammonia emissions from beef feedyards.
A comparative spectral analysis of the organic matter in beef and dairy manures, feedyard pen manure pack layers, feedyard retention ponds, and dairy lagoons was conducted. Ultra violet-visible and Fourier transform infrared spectroscopic analysis of these samples revealed large differences in the composition and complexity of the organic matter from the manure types. These differences in organic matter could affect soil fertility when these manures are applied to fields as fertilizer.
Cooperative cattle feeding studies were conducted at three universities and samples of diets, feces, and manure were collected. These samples, as well as samples from cooperating feedyards and other cooperative feeding studies have been analyzed for dry matter, nitrogen, phosphorus, carbon, and acid insoluble ash so that nutrient excretion and volatilization losses can be determined/estimated.
Three respiration calorimetry studies were conducted to evaluate the effects of corn processing method and wet distiller's grain on energy utilization and enteric methane emissions from cattle fed corn-based finishing diets. Enteric methane emissions were less, and energy retention was greater, when cattle were fed diets based on steam flaked corn than when fed diets based on dry rolled corn. Replacing corn with 15 to 30% wet distiller's grains did not affect enteric methane emissions or energy retention when dietary fat levels were held constant. However, feeding diets containing 45% wet distiller's grains increased enteric methane production by 30%. Under the conditions of these experiments, the net energy values of wet distiller's grain were similar to steam flaked corn. This information is useful to feedlot nutritionists for formulating cattle finishing diets and to policy makers for predicting enteric methane emissions from feedyards.
Net energy values determine din these studies will be used by nutritionists to better formulate and balance finishing diets and to better predict animal performance.
Lab scale odor production studies were conducted by scientists at the USDA-ARS-Meat Animal Research Center using feces and urine from cattle in the respiration experiments. Production of odorous volatile organic compounds was affected by grain processing method and by feeding of wet distiller's grains.