Location: Livestock Nutrient Management Research2011 Annual Report
1a. Objectives (from AD-416)
To determine, in cooperation with scientists from Texas AgriLife Research, Kansas State University (KSU), 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 these emissions.
1b. Approach (from AD-416)
Ammonia emissions will be measured at two commercial beef cattle feedyards 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 one commercial feedyard 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 constructed 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 emission 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 chamber on feedlot plots.
3. Progress Report
Accurate estimates of ammonia emissions from beef cattle feedyards are needed as regulatory requirements and the need for accurate emissions inventories increase. ARS researchers from the Conservation and Production Research Laboratory, Bushland, TX, semi-continuously measured ammonia and methane emissions at 2 commercial feedyards using open path lasers and an inverse dispersion model. Monthly ammonia-nitrogen (N) loss, as a fraction of fed N, agreed with previous results and ranged from 19 to 85% of fed N. The fractional loss and per capita emissions during winter months was approximately 50% of losses during summer months. These measured losses were substantiated using total N balance. Feeding distiller's grains (DG) at 1 feedyard increased crude protein content of the diet from 13 to 19%, and increased mean monthly ammonia emissions by 44 to 144%, compared with the feedyard with corn-based rations. Methane concentrations and flux were measured at 1 feedyard for 12 months. Preliminary data indicated that diel methane concentration over the retention pond was bimodal, with pre-dawn and pre-midnight peaks. Quantifying the variability of ammonia and methane emission rates and impact of factors that affect them will yield databases for scientists to validate and verify process models of emissions, provide the cattle industry with accurate science-based emissions data to meet regulatory requirements, and give regulators more accurate, comprehensive data from which to build emissions inventories. A series of symposia were conducted in late 2010 at 2 locations in Texas and 1 in Kansas to disperse results to cattle producers, consultants, and NRCS representatives. Cooperative cattle feeding studies were conducted at 3 universities, and samples of diets, feces, and manure were collected. These samples along with samples from cooperating feedyards and earlier feeding studies are currently being analyzed for dry matter, N, phosphorus, carbon, and acid insoluble ash so nutrient excretion and volatilization losses can be determined/estimated. Two respiration calorimetry studies were conducted to evaluate effects of corn processing method and wet distiller's grain (WDG) on energy utilization and enteric methane emissions from cattle fed corn-based finishing diets. Enteric methane emissions were lower and energy retention was higher with diets based on steam-flaked corn (SFC) than diets based on dry rolled corn. Replacing corn with 30% WDG did not affect enteric methane emissions or energy retention. Under these experiment conditions, net energy values of WDG were similar to SFC. These net energy values can be used by nutritionists to better formulate and balance finishing diets and to better predict animal performance.