Location: Livestock Nutrient Management Research2021 Annual Report
Objective 1: Characterize and improve prediction of ammonia and greenhouse gas emissions from cattle production systems. Subobjective 1A. Characterize methane (CH4) emissions from southern Great Plains grazing systems. Subobjective 1B. Assess the impact of environmental conditions and management practices and their interactions on emissions of NH3 and GHG from open lot cattle production systems. Subobjective 1C. Improve NH3 and GHG emissions measurements for feedyards and dairies. Objective 2: Improve feed nutrient use in cattle to maintain animal productivity, reduce emissions of ammonia and greenhouse gases, and mitigate pathogens and antibiotic resistant bacteria. Subobjective 2A. Determine effects of cattle diet on enteric CH4 production. Subobjective 2B: Evaluate and improve models to predict enteric CH4 emissions from grazing and feedyard cattle. Subobjective 2C. Identify and quantify sources of enteric nitrous oxide (N20) emissions from cattle in respiration calorimetry chambers. (NEW 2019) Subobjective 2D: Develop alternative strategies that reduce methane emissions while maintaining production. Research Goal 2D.1: Quantifying the impact of supplements in animal diets, such as fungal based probiotics, seaweed and condensed tannins, on enteric methane emissions, and establishing the biochemical and/or physiological mechanisms responsible for emission reductions. Research Goal 2D.2. Quantifying the impact of new technologies and animal management systems on enteric methane emissions. Objective 3: Manage soil and manure reactive nitrogen, phosphorus and carbon to improve soil properties, reduce nutrient loss and mitigate pathogens and antibiotic resistant bacteria. Subobjective 3A. Evaluate the effectiveness, practicality and economics of chemical inhibitors and manure amendments to reduce N20 and NH3 emissions from beef cattle feedyards, dairies, and manure-amended soils. Subobjective 3B. Quantify field-scale emissions of N20 from manure-amended soils. Subobjective 3C. Establish protocols for examining AR in agroecosystems. Subobjective 3D. Characterize forms of P in manure-amended soils. Subobjective 3E: Evaluate soil C/N change with land use on the southern High Plains.
Beef and dairy cattle production provide vital human nutrition and important economic activity. Cattle production, like all human endeavors, also contains environmental risks. This multidisciplinary research will help us to better understand and mitigate the environmental risks from cattle production systems on the Southern Great Plains. We will quantify and improve predictions of emissions of ammonia (NH3) and greenhouse gases (GHG) from cattle production systems. The research will focus on the predominant agricultural GHG emissions of methane (CH4) and nitrous oxide (N20). Sources of these emissions include grazing animals (enteric emissions), emissions from cattle, pen and lagoon surfaces at beef feedyards and dairies, and emissions from soils following land application of manure. We will determine the effects of cattle diet on enteric GHG emissions on scales that range from single animal to whole pastures, feedyards or dairies. We will test potential mitigation methods to reduce emissions from manure surfaces and cropped fields using controlled laboratory experiments followed by pilot-scale and field-scale experiments. We will quantify the changes in soil carbon (C), nitrogen (N), and phosphorus (P) from application of manure or land use change. A collaboration of ARS laboratories will test methods to characterize antibiotic resistant (AR) bacteria and genes from manure-impacted soil. Research results will provide science-based information and technologies for livestock producers, extension specialists, and regulators to protect air quality, manage feedyard and dairy manure, enhance production efficiency, and improve sustainability of livestock production.
Researchers at Bushland, Texas, completed the following research over the 5-year life of the project 3090-31630-005-00D “Improved Practices to Conserve Air Quality, Maintain Animal Productivity, and Enhance Use of Manure and Soil Nutrients of Cattle Production Systems for the Southern Great Plains.” Objective 1: In collaboration with USDA-ARS in El Reno, Oklahoma, project scientists developed methods to measure enteric methane (CH4) emissions from cow-calf pairs grazing winter wheat to characterize seasonal emissions and the effects of forage quality for a USDA-National Institute of Food and Agriculture Coordinated Agricultural Project (Great Plains Grazing CAP). Enteric CH4 from brood cows grazing long-grass prairie and growing yearling-cattle on a hay-based diet had lower rates of enteric CH4 production when hay quality and crude protein content of the forage were greater. Cattle fed finishing diets produced less enteric CH4 when fed higher quality, lower-forage diets. To assess the impact of technique on measured enteric CH4 emissions, project researchers compared previously published results from respiration chambers (whole animal) to those determined by either sulfur hexafluoride or Greenfeed systems: CH4 emissions were lower when measured from respiration chambers. Respiration chambers were also used to produce the first quality data on enteric nitrous oxide (N2O) production. To determine how environmental factors and manure properties effect greenhouse gas (GHG) emissions from beef cattle manure, project scientists cooperated with Texas A&M AgriLife to develop novel laboratory techniques that enabled pilot-scale (1 m2) gas emissions measurement from manure or manure-amended soil under controlled conditions. This significant advance in methodology allowed for multiple opportunities for new avenues of research. Manure land application studies showed that incorporation of manure, a common practice to reduce ammonia (NH3) emissions, increased N2O emissions, and this was more pronounced after rainfall. In addition to emissions from cropland, cattle facilities are sources for GHG. Scientists examined seasonal emissions from cattle pens at multiple commercial feedyards in collaboration with Texas A&M AgriLife Research and New Mexico State University. Climate has a large effect on N2O emission from feedyard pen surfaces. Rainfall on pen surfaces resulted in a rapid increase in N2O emissions, which supported earlier results from flux chamber studies. After rainfall, studies showed a second flush of N2O from pen surfaces that occurred approximately a week after rainfall: likely due to increased microbial activity and rates of nitrification and/or denitrification. However, saturating rainfall decreased N2O emissions. Temperature was a major driving factor with N2O emissions increasing sharply when manure temperatures exceeded 30° C. The average CH4 loss rate was less than 1 percent of annual GHG emissions (expressed as carbon dioxide equivalents). Collected data were then used to modify a new empirical model of GHG emissions from open-lot cattle systems. Other historical measurements collected from commercial feedyards were used for modeling efforts by project scientists and those at USDA-ARS University Park, Pennsylvania, and University of New Hampshire. These efforts led to improvements in two process-based models for predicting NH3 and N2O emissions from open-lot cattle manure. These results showed the complexity of N2O production and changes in microbial community structure based on temperature and rainfall. Early in the project, scientists conducted studies to determine how zeolite or other pen amendments impact NH3 emissions. Zeolites and other amendments had high, but transient, reduction in NH3 volatilization that could limit economic or practical feasibility. Towards the end of this project, ARS scientists and those from West Texas A&M University and Texas A&M AgriLife began new studies to characterize and improve prediction of NH3 and GHG from cattle production systems with the multi-location ARS Dairy Agroecosystems Working Group (DAWG). These studies focused on effects of manure application on gaseous emissions, soil health and crop productivity. The work included both greenhouse and small plot studies with feed crops grown under varying manure rates. Objective 2: Project scientists worked to improve feed nutrient use in cattle while maintaining animal productivity, reducing emissions of NH3 and GHG, and mitigating pathogens and antibiotic resistant bacteria. The effects of pen cleaning frequency on GHG emissions were evaluated: there was a short-term increase in N2O emissions immediately following removal of manure from the pen surface. Plant tannins have shown promise in reducing GHG emissions from various agricultural activities, but data were lacking on the effects of plant tannins on GHG emissions from dairy cattle manure. ARS scientists and those from Texas A&M AgriLife Research analyzed the effects of the addition of condensed and hydrolysable tannins. Application of condensed tannins to manure reduced N2O and CH4 emissions but the effects varied with tannin type. Studies assessed feed additives and alternative feedstocks to reduce enteric CH4 emissions and improve nutrient utilization by cattle. Specifically, in vivo and in vitro studies evaluated malted barley and seaweed supplementation on gaseous emissions and rumen function in cannulated Angus-cross breed steers. Laboratory in vitro studies with rumen fluid examined the effect of malted barley supplementation rate on fermentation patterns and emissions of CH4, N2O and other gases of concern (i.e., hydrogen sulfide). In addition, a series of in vivo and in vitro experiments quantified the effects of malted barley on feed intake, rumen fermentation rate, dry matter digestibility, ruminal in vitro gas production, and rumen microbiome diversity. Analyses to date indicate that only red seaweeds (Asparagopsis species) contain bromoform, a suspected anti-methanogenic compound. Grain processing and specific grain type caused differences in its digestibility. Researchers conducted studies to see how substituting steam-flaked corn for steam-flaked wheat affected rumen function. Overall, the wheat diet led to higher enteric GHG emissions than corn. Steam-flaked wheat had no substantial environmental value (in terms of GHG emissions) or animal productivity value over steam-flaked corn. Objective 3: Studies investigated manure effects on soil nutrients, pathogens, and antimicrobial resistant bacteria on the Southern High Plains. The transfer of antibiotic resistance genes (ARG) is a large concern for the agricultural community and the public in general. Project researchers along with scientists from University of Pennsylvania compared feces from an assortment of fowl and livestock systems to characterize antibiotic residues, ARG and microbial diversity. Project researchers and ARS scientists from Lincoln, Nebraska, evaluated ARG after land application of manure to understand transport of manure-derived antibiotic resistance from agricultural systems. Research examined genes that transmit resistance for b-lactamase, tetracycline, macrolide, sulfonamide, and integrase. This work showed the potential for temporary ARG "blooms" right after manure application. Interestingly, ARG were unevenly distributed in the soils, which makes it hard to say if they came from manure or were already present as background soil fauna. This work led to a recommendation for normalized quantitative PCR (qPCR) ARG values, expressed as the number of ARG targets per 100,000 16S ribosomal RNA genes. Investigations to characterize soil organic matter continued. The concept of soil health is largely related to the quantity of labile soil carbon present. Labile soil carbon has been proposed to be a sensitive indicator of soil carbon stocks. Increasing labile carbon is difficult in semi-arid systems with limited precipitation. Advances in instrumentation and techniques allow for in-depth study of soil carbon and its components. Investigations on long-term dryland cropping systems indicated that traditional and conservation-based methods of cropping in water-limited, semi-arid areas may be insufficient to remediate or recover labile soil carbon. Manure microbes influence N2O losses from beef cattle feedyards. A group of researchers from ARS in Bushland, Texas, Clay Center, Nebraska, and Lincoln, Nebraska, evaluated the microbial community in beef manure and its relationship to factors and processes involved in N2O production. Collaborative research evaluated how sampling depth, time, temperature, and water content affected the microbial community of feedyard manure. The Firmicutes bacteria showed increased populations that coincided with high N2O fluxes following water addition and increased temperatures. Gene copies of the rate limiting enzyme from bacteria were greater than those from fungi, possibly indicating that bacteria are more important than fungi to controlling N2O emissions from beef manure. Research continued regarding phosphorus cycling in soils amended with livestock manure. In collaboration with ARS scientists at Auburn, Alabama, project scientists evaluated the effects of long-term poultry litter application on specific phosphorus forms in a soil with high mineral content. In this study, an Alabama Ultisol that received over 10 years of broiler litter application was analyzed by sequential fractionation and phosphatase hydrolysis. Litter application increased concentrations of mineral-bound organic phosphorus; however, tillage type also played a key role, with surface accumulation of stable, organic phosphorus in no-till soils.
1. Greenhouse gases from Southern High Plains beef cattle feedyards are affected by climate. Nitrous oxide and methane are greenhouse gases (GHG) that have been linked to climate change. High concentrations of nitrogen and carbon make livestock manure at beef cattle feedyards a source of GHG emissions. Scientists from USDA-ARS in Bushland, Texas, and Clay Center, Nebraska, Texas A&M AgriLife Research, Texas Tech University and University of Minnesota studied how GHG are affected by deposition of rainfall, urine and feces. Nitrous oxide emissions from the moisture in urine and feces were smaller than those from precipitation, ranging from 16 percent for feces to 33 percent for urine. The emissions were still large enough to be included in annual emission estimates. Unlike our earlier research, which shows that GHG emissions increased following smaller (0.5- to 1-inch) rainfall events, GHG emissions dropped below detection levels for 10 days following a 3-inch rainfall event that saturated the pen surface. These data will be used to refine models and update greenhouse gas emission inventories for beef cattle feedyards.
2. Steam-flaked corn and high-quality hay lower greenhouse gas emissions from cattle. Methane, nitrous oxide and carbon dioxide are greenhouse gases that have been linked to climate change. When added together, the global warming effects of these three gases make up the carbon footprint. Scientists from USDA-ARS in Bushland, Texas, Woodward, Oklahoma, and El Reno, Oklahoma, West Texas A&M University, Texas A&M AgriLife Research, and Texas Tech University studied how dietary ingredients affect the carbon footprint of cattle. Scientists determined that GHG emissions were lowered when cattle consumed a diet based on high quality hay. Corn, a typical feedlot diet ingredient, is usually processed either by dry rolling or steam flaking prior to being fed. Feeding steam flaked corn reduced the carbon footprint by 9 to 13 percent. Steam flaked corn also reduced enteric methane emissions by 30 percent. Diet manipulation can be an effective method for reducing emission of greenhouse gases from cattle. Therefore, high quality grass hay is preferred to low quality hay for reducing the carbon footprint of grazing cattle, and steam flaking of corn is preferred to dry rolling for reducing the carbon footprint of feedyard cattle.
3. Antibiotic resistance genes found in feces of pasture raised livestock and poultry. Animal manure can be a source of antibiotic resistant genes (ARG); however, few studies have evaluated the presence of ARG in pasture-raised animal production systems. Therefore, scientists from USDA-ARS in Bushland, Texas, and Athens, Georgia, and University of Pennsylvania, analyzed the presence of ARG in feces collected from pasture-raised livestock and poultry systems. Results indicated that the ARG in layer hen manure were the highest, followed by broiler chickens, swine and beef cattle. These data indicate ARG concentrations in feces varied from farm-to-farm and from animal type-to-animal type. Pasture-raised animals provide background information on the presence of specific ARG in soils when animals do not receive antibiotics or other pharmaceuticals. These baseline data are crucial for tracking ARG fate and transport in manure-amended soils, thus are of interest to peer scientists, livestock industries and the general public.
4. Nitrous oxide emissions from beef feedyard pens are highly variable and depend on specific manure properties. Beef cattle are brought to large (up to 100,000 cattle) open-lots. These animals are kept in soil-surfaced pens for about six months while they put on weight before processing. During this time the manure they produce accumulates in the pens and is a source of nitrous oxide, a greenhouse gas. Feedyard emissions of nitrous oxide is significant but is poorly understood. Only a few studies have looked at the specific biological processes that produce nitrous oxide in manure. Scientists from USDA-ARS in Bushland, Texas, Clay Center, Nebraska, and Lincoln, Nebraska, and Texas A&M AgriLife Research conducted a laboratory study to determine the role of nitrification and denitrification on manure nitrous oxide emissions. Results suggest that most feedyard nitrous oxide comes from the top 5 cm of the manure pack and is produced by denitrification about two weeks after a rainfall event. This suggests that mitigation methods, such as amendments or inhibitors, should largely target the manure surface in a feedyard.
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