Performing Department
(N/A)
Non Technical Summary
In the U.S., agriculture is responsible for 9.4% of total greenhouse gas (GHG) emissions (EPA, 2023). That same report states that in 2021, methane produced from enteric fermentation in the U.S. accounted for 194.9 million metric tons (MMT) of carbon dioxide equivalent (CO2Eq.). This represents 3.1% of the total U.S. emissions, or 33% of total agricultural emissions. However, given the size of the livestock sector, in 2021, methane produced from enteric fermentation in the U.S. was equivalent to 66% of the total GHG of Spain. When contrasting the contribution of this important segment of the U.S. economy with the total GHG emissions of an industrialized country like Spain, which in addition has a sizeable agricultural industry, it becomes evident that there is an imperative need to address enteric methane emissions domestically to contribute globally to one of the greatest challenges of all times: sustainable food production for an ever-growing population.As we move toward the next couple of decades, the world's agriculture will face one of the greatest challenges of all time: to produce enough food to feed the 9 billion people the earth will hold by 2050. Without question, this will demand the concerted efforts of producers, researchers, and policymakers to provide the experience, technology, and legal framework necessary to accomplish such a difficult endeavor. Among the different sources of animal protein, beef is the most nutrient dense on a per calorie basis, supplying several of the essential vitamins and minerals with a relatively low caloric intake per serving.Ruminants such as cattle, sheep, and goats have a unique advantage over non-ruminants in terms of nutritional physiology, because they carry microorganisms in their gastrointestinal tract (GIT) that hold the key to the digestion of fiber. Fiber is present in forages in the form of cellulose and is the most abundant complex carbohydrate on earth. By harboring microorganisms in their GIT, ruminants can take advantage of fiber digestion by creating a symbiotic relationship between the microbes and the ruminant host. The microbes digest the fiber and produce by-products known as volatile fatty acids, which are in turn used by the ruminant animal as an energy source. In return, the ruminant host provides a good environment for the microorganisms and plenty of feed to sustain their growth. For this reason, cattle, sheep, and goats can thrive in environments where no other type of production system can take place.Unfortunately, this advantage by ruminants in terms of their ability to digest fiber comes at a cost. The production of greenhouse gases such as carbon dioxide and methane is a result of the enteric fermentation of feedstuffs, and those greenhouse gases are released by cattle as a necessary byproduct of their fermentation of fibrous feeds. The "greenhouse effect" of certain gases refers to their ability to "trap" the heat that is generated when the sun radiation bounces back after hitting the earth's surface. That radiation cannot escape, and thus increases the atmospheric temperature, affecting biological processes in diverse manners. Those gases with such capacity to retain heat are called Greenhouse Gases (GHG), and the three most common gases are carbon dioxide, methane, and nitrous oxide.The ability to produce methane, the main contributor of the GHG emitted by cattle, is much greater in animals consuming forage than those consuming a high-grain diet. Thus, segments of beef production chain that involve the use of forages as the main resource are greater contributors in terms of GHG emissions.Beef and dairy cattle, swine, horses and small ruminants are all contributors to the 194.9 MMT of CO2Eq. produced via enteric fermentation in the U.S. However, beef cattle are the greatest contributors by far, with 71% of total enteric methane, distantly followed by dairy cattle which contribute with 25% of those emissions (EPA, 2023). Based on these statistics, research efforts to mitigate enteric methane emissions should begin to focus more on beef production systems, and particularly those segments of the industry in which forages play a large role (e.g., cow-calf, stocker, etc.).Currently available strategies to mitigate methane are very few, and most of them are facing regulatory challenges because of the nature of their production (e.g., synthetic molecules) or because of potential toxicity (e.g., macroalgae feeding). The two most promising feed additives for enteric methane mitigation in the U.S. are either not approved as of yet, or may pose additional challenges in terms of food safety or environmental impact. It is quite concerning that the future sustainability of animal production systems in terms of carbon footprint, relies on such few tools, and almost none with the potential for immediate widespread use and impact. To guarantee the long-term sustainability of livestock systems in the U.S., action needs to be taken immediately to promote the development of a greater portfolio of feed additives with potential to decrease methane emissions.This project is poised toOur long-term goal is to reduce the enteric CH4 emissions in the U.S. livestock industry with concomitant improvements in the sustainability of cow-calf and stocking systems. Our overall objective is to develop the next generation of safe, efficacious, and affordable feed additives to mitigate enteric methane emissions in ruminants. We are particularly well prepared to conduct the proposed research due to our unique access to multiple research herds and facilities to simultaneously conduct the multiple studies required to meet our objectives. In addition, we have assembled a team that combines ruminant nutritionists, forage agronomists, chemists, biochemists, microbiologists, and Extension State Specialists, each of whom has vast expertise and publications records in the different areas of this project. Thus, the available resources and complementary expertise of our group are especially conducive to the successful completion of the proposed investigations.We plan to accomplish our overall objective for this project by pursuing the following four supporting objectives:Objective 1: Production and purification of immunogens and 2-hydroxyethylphosphonate (HEP) Objective 2: Optimization of the dose and impact on microbiome and digestibilityObjective 3: Deployment and delivery of new additives Objective 4: Extension and Outreach to assess adoption rate and impact on stakeholdersThe expected results from this study are that these additives may contribute to a reduction of a minimum of 25% in U.S. enteric methane emissions, which would amount to 48 million metric tons of carbon dioxide equivalent per year. Put in context, these emission reductions are equivalent to the total emissions produced by the state of Nebraska in one year, including all the different segments of the state's economy (energy, transportation, agriculture, etc.).The anticipated impact of this project is the ability to maintain the current levels of animal protein production that have made the U.S. agriculture so competitive over the years, while reducing significantly the emissions associated with it. The world is currently desperately searching for alternatives to decrease the carbon footprint of food production. The development of affordable and ready-to-use additives for the livestock industry with the potential to decrease enteric methane will position the U.S. as a leader in climate-smart agriculture, while providing its producers with a competitive advantage in terms of technology.
Animal Health Component
30%
Research Effort Categories
Basic
50%
Applied
30%
Developmental
20%
Goals / Objectives
Our long-term goal is to reduce the enteric CH4 emissions in the U.S. livestock industry with concomitant improvements in the sustainability of cow-calf and stocking systems. Our overall objective is to develop the next generation of safe, efficacious, and affordable feed additives to mitigate enteric methane emissions in ruminants.We plan to accomplish our overall objective for this project by pursuing the following four supporting objectives:Objective 1: Production and purification of immunogens and HEP Objective 2: Optimization of the dose and impact on microbiome and digestibilityObjective 3: Deployment and delivery of new additives Objective 4: Extension and Outreach to assess adoption rate and impact on stakeholders
Project Methods
Objective 1: Production and purification of immunogens and 2-hydroxyethylphosphonate (HEP) Obj. 1a: Identification and purification of target immunogens to produce avian polyclonal antibody preparations.Antibodies against whole cells and/or membrane fragments of ruminal methanogensWhole cells or membrane fragments of methanogens can be used to induce avian PAP. Using this approach, antibodies can be quickly produced allowing field testing trials. Ruminal methanogens will be grown according to procedures available in the literatureAntibodies against methanogen target peptides or proteins/protein domains expressed in Escherichia coliWhile raising antibodies against whole cells and/or membrane fragments of methanogens is viable, a more targeted approach focusing on specific methanogenic surface proteins may elicit a stronger and more specific immune response. Several extracellular methanogen protein targets have been identified and validated as targets of antibodies for methane mitigation.Antibodies against specific methanogen proteins or protein domains expressed in M. maripaludisNot all methanogen proteins express well in E. coli. Also, if there are any methanogen-specific post-translational modifications of the target proteins (e.g., glycosylation), the mature proteins must be expressed in a methanogen host. There are two well-established methanogenic systems for heterologous protein expression: Methanosarcina acetivorans and Methanococcus maripaludis.Antibodies against specific proteins isolated directly from ruminal methanogens.Sometimes even the expression of methanogen proteins in a methanogen host does not always work. If needed, individual ruminant methanogens will be grown, and specific proteins will be isolated from the membrane fraction for use in antibody development. Some target membrane proteins have been well characterized in the literature and assays have been developed that can be used to identify enriched protein fractions. Where no activity assays are available, mass spectrometric fingerprinting will be used for protein identification.Obj. 1b: Mass production of avian polyclonal antibody preparations (PAP)The partnership with Camas Inc. in this grant proposal will be crucial for the development of PAP based on the target immunogens produced.Obj. 1c: Testing and production of 2-hydroxyethylphosphonate (HEP)In the proposed research, the potential of several HEP-based methane mitigation strategies in cattle will be evaluated. These strategies will include 1) direct use of HEP as a feed additive, 2) feeding of dried mycelia of wild-type and engineered Streptomyces strains (over)producing HEP, and if successful 3) engineering of native Streptomyces spp. in the cow/cattle microbiome for the stable production of HEP.Objective 2: Dose-response studies to assess optimal dose for methane mitigation, microbiome changes, and impact on nutrient digestibilityExperimental design and enteric CH4 measurements: These studies will be conducted simultaneously at the University of Florida and at Clemson University to assess a dose-response for each novel additive. Angus crossbred steers, cows, or growing heifers will be used in each of the studies, depending on the production system being assessed. The series of studies to be conducted at both universities will adopt a similar experimental design: a replicated 4 × 4 Latin square, and measuring the same variables: enteric methane emissions, ruminal microbiome changes, and total tract nutrient digestibility. These variables will provide a complete assessment of the potential of each additive to impact methanogenesis and performance. Variables of interest in terms of methane will be methane yield (per unit of DM intake), and methane per unit of OM digested. For the assessment of enteric CH4 emissions, all studies will include the use of GreenFeed units (C-Lock Inc., Rapid City, SD), located at the University of Florida-NFREC, and Clemson University.Ruminal microbiome analyses: Microbial functions will be monitored by 16S metagenomics and shotgun sequencing of samples collected from each animal at the beginning and end of each experimental period. To understand the bacterial community, a dual-index sequencing strategy will be used (Kozich et al., 2013). Briefly, the V4 region of the 16S rRNA gene will be amplified by polymerase chain reaction (PCR) with dual-index primers (Kozich et al., 2013).Total tract digestibility of nutrients: Apparent total tract digestibility of nutrients will be assessed during the last 5 d of methane emissions collection. This technique is routinely used by the DiLorenzo research group and involves the collection of feed and fecal samples for 4 continuous days in the morning and afternoon to create a composite within animal. Indigestible neutral detergent fiber (iNDF) will be used as an internal digestibility marker, after a 288 h in situ ruminal incubation (Krizsan and Huhtanen, 2013). Apparent total tract digestibility of dry matter, organic matter, crude protein, neutral detergent fiber, acid detergent fiber, and starch (when appropriate) will be calculated.Cow-calf phase: Studies to assess the impact of developed feed additives on cow-calf systems will be conducted over 2 years and studies will be divided into 3 measurement periods (in chronological order from the beginning of calendar year): a) grazing of winter annual forages, b) summer grazing of warm season perennial forages, c) hay feeding during fall forage gap.Stockpiling phase: Stockpiling is a practice that is gaining ground among beef producers, in an attempt to reduce feed costs and better utilize forage resources. The best two treatments from the dose-titration studies will be tested in a grazing setting using stockpiled 'Gibtuck' limpograss (Hemarthria altissima), which is a commonly used grass in beef operations in the southeastern U.S. The third treatment will be the control, without using any feed additive. Treatments will be allocated in a randomized complete block design, with three blocks. Each one of the nine experimental units (pasture) will measure 1 acre and have water and minerals available.Backgrounding phase: These production segments are becoming more and more relevant in the U.S. beef production system, due to the continued increase in beef cattle harvest weights. The use of silages and byproducts in this segment is very common, not only in the Midwest but also in many regions across the U.S. Enteric methane mitigation in this segment will be addressed at the University of Florida and Clemson University. Studies in this phase will include conserved winter forages fed to replacement beef heifers (Clemson) and corn-silage and byproduct-based diets fed to growing steers and heifers (UF). In all cases methane emissions will be measured using the GreenFeed System (C-Lock Inc.), and feed intake and animal growth performance will be measured on an individual basis.Feedlot finishing studies: A feedlot finishing study will be conducted at the University of Florida, Feed Efficiency Facility to assess the methane mitigation impact in this phase. A total of 120 Angus crossbred steers will be used in a randomized block design with 24 concrete-floored pens (111 m2 each) of 5 steers each, and 6 pens/treatment. Pen will be considered the experimental unit, and four treatments will be tested in each study (the three most promising additives/dose from all previous phases, plus a control). Steers will be fed ad libitum a feedlot finishing diet comprised of (DM basis) 70% dry-rolled corn, 15% dry distillers grains plus solubles, 5% cottonseed hulls, 5% ground hay, and 5% of a vitamin-mineral supplement containing monensin. Enteric methane will be measured using the GreenFeed system and feed intake will be monitored using SmartFeed bunks (C-Lock Inc.). Feed intake, average daily gain, feed conversion, and methane emissions intensity will be assessed for each additive.