Location: Forage-animal Production Research
2024 Annual Report
Objectives
Objective 1: Determine how secondary metabolites influence positive and negative changes in grazing livestock physiology; and how biological and genetic factors influence the incidence of fescue toxicosis and develop strategies to reduce impacts.
Sub-objective 1.A: Investigate the interaction of serotonin and ergot alkaloid exposure to determine if serotonin can compete with EA at the receptor level.
Sub-objective 1.B: Determination of the optimum dose of L-DOPA, and the use of L-DOPA to mitigate the decrease of feed intake provoked by EA.
Sub-objective 1.C: Determine the effect of leucine, glucose, and acetate infusion on mTOR pathway activation in muscle and adipose tissue, determine infusion rates of leucine, glucose, and acetate required to achieve submaximal and maximal activation of mTOR and downstream proteins in muscle and adipose tissue, determine the effects of fescue-derived alkaloids on muscle and adipose mTOR activation.
Sub-objective 1.D: Use remote sensing technology to generate a phenotype of ergot alkaloid exposure that can be used to characterize genetic tolerance to these toxins.
Objective 2: Effects of clover isoflavones on development, finishing and meat quality in fescue-based pastures.
Sub-objective 2.A: To determine the effect of isoflavone supplementation via red clover during post-weaning management on nutrient utilization and performance of grazing and confinement-finished lambs.
Sub-objective 2.B: Examine the effect of isoflavone supplementation during post-weaning management on carcass traits, muscle proteome, and meat quality of grazing and confinement-finished lambs.
Sub-objective 2.C: Evaluate the impact of dietary isoflavone supplementation on the rates of antimicrobial resistance (AMR).
Objective 3: Identify the impacts of environmental and nutritional adaptation on development and develop strategies to improve reproductive and growth performance.
Sub-objective 3.A: Investigate the impacts of pre-weaning nutritional management on microbial development, health and performance of beef calves and lambs.
Sub-objective 3.B: Investigate the role of adaptation to grazing system and environment on rumen microbial communities, nutrient utilization, reproductive, and growth performance in first calf beef heifers.
Sub-objective 3.C: Determine how ergot alkaloid exposure, grazing system, and environment influence calf microbial development, health, and performance.
Sub-objective 3.D: Evaluation of the form of supplemental selenium to ameliorate fescue toxicosis in lactating beef cows consuming toxic E+ TF (TF).
Sub-objective 3.E: Manipulation of the form of supplemental selenium (Se) to increase fertility in beef cattle.
Approach
Forages are a key component to many livestock production operations. There are numerous bioactive compounds in forages that are consumed by grazing animals. Some of these compounds benefit the pasture at the expense of the grazer. Others have beneficial effects in the plant as well as the animal, but their efficacy may be limited to certain production settings. The overall goal of this project plan is to study bioactive compounds consumed during grazing at the microbial and animal levels to improve productivity and sustainability of forage-based enterprises. Ergot alkaloids (EA) are mycotoxins frequently found in pasture grasses and are credited with imparting persistence that makes tall fescue (TF) grass very sustainable. Unfortunately, EA also cause fescue toxicosis, an ergotism syndrome with significant negative impacts on animal productivity and welfare that is not completely understood. Conversely, isoflavones are legume-derived secondary metabolites that have been shown to have antimicrobial activity, growth promotion potential, and the ability to mitigate negative effects of EA. Isoflavones are phytoestrogens and their potential influences on livestock reproduction and on muscle development and composition are of interest. How phytochemicals integrate into livestock management practices is also important. Exposure of naïve livestock during gestation or grazing to EA and isoflavones, phytochemical influences on development and production, and interactions with mineral supplements are not clearly defined. These unknowns will be studied at the animal and gut microbial levels, in stocker steer, cow-calf and small ruminant models. They will be evaluated at genetic, genomic, cellular, tissue, and whole animal aspects. The research results will be both an improved mechanistic understanding of pasture-based phytochemicals and transferable technologies that minimize negative and maximize positive attributes. As pasture forages and their secondary metabolites continue to be optimized, researchers will have better tools to offer livestock producers allowing them to produce more with less.
Progress Report
For Sub-objective 1.A, all myograph experiments have been completed. The ergovaline accumulation analysis has been completed. We have been able to show that as the level of ergovaline in the incubation media increases the amount of ergovaline recovered from the vein also increases and is independent of the amount of serotonin in the media. A manuscript is being prepared.
For Sub-objective 1.B, experiments have been conducted, data analyzed, and paper published. L-DOPA supplementation did moderately raise feed intake in cattle with fescue toxicosis. A manuscript has been published.
For Sub-objective 1.C, a post-doctoral associate was hired in April and experimental plans are actively being made. Progress in expected later in fiscal year 2024.
For Sub-objective 1.D, phenotype, blood samples, weather data and pasture data have been collected from 300+ animals to date.
For Sub-objective 2.A Hypothesis 2A.1, year 1 grazing experiment is completed and pasture and animal samples have been analyzed. Year 2 grazing experiment is scheduled to start July 2024. Hypothesis 2A.3.: Year 1 of Experiment #1 is completed. All samples have been analyzed.
For Sub-objective 2.B, all of Experiment 1 has been completed. The longissimus muscles from lambs have been collected 24-h postmortem and subjected to retail storage under refrigeration. Instrumental color and biochemical attributes have been evaluated. Manuscripts are being prepared. Year 2 has not be initiated. The associated grazing study is scheduled to start in July 2024. Findings indicate that feeding milk replacer can be successfully utilized as an artificial raising strategy in lamb production without compromising fresh meat color. Additionally, results suggest that supplementation of red clover can be a promising feeding strategy in lamb production without compromise of the fresh lamb meat color.
For Sub-objective 2.C, samples from lamb carcasses have been analyzed for tetracycline-resistant bacteria. Results were very high for resistant bacteria.
For Sub-objective 3.A, year 2 of the field experiment is complete. All cow and calf performance data, rumen, fecal, blood, and forage samples were successfully analyzed from Year 1. Hypothesis 3A.2.: Year 2 of the experiment is complete. All ewe and lamb performance data, rumen, fecal, blood, and feed samples were successfully analyzed from Year 1.
For Sub-objective 3.B, heifers from Montana have been received and Year 1 of sample/data collection is ongoing.
For Sub-objective 3.C, heifers from Montana have been received and have been successfully bred.
For Sub-objective 3.D, Non-Assistance Cooperative Agreement-funding has been delayed as a consequence of the Princeton, Kentucky, farm not back to a fully functional status following the tornado damage sustained in December 2021. Pastures have been fertilized and cows are scheduled to be bred and sampled in summer of 2025.
For Sub-objective 3.E, animals have been purchased and graduate student has been identified who be responsible for the analyses. The heifers are currently in the “adaptation” phase of the selenium supplementation program – that takes more than six months. Once this is completed, the heifers will be bred and killed as indicated in the sub-objective.
Accomplishments
1. Compared diarrhea-causing bacterium, C. difficile, to its relatives. To compare similar living things to each other, they must be grown in the same way. Bacteria are in solid or liquid media that is like a broth. Clostridioides difficile, commonly called C. diff, causes life-threatening diarrhea in humans, horses, and calves. It is well studied in medical laboratories, but many of its close relatives are harmless bacteria from the bovine gastrointestinal tract. ARS scientists in Lexington, Kentucky, examined the growth and waste products made by C. diff in the media that are typically used to grow its relatives. This research allows us to compare C. diff to its cousins that do not cause disease to better understand the basic biology of both. By comparing C. diff to related bacteria we can learn how to prevent it from growing and causing disease.
2. Discovered gut microorganisms of exercising mice reduce muscle atrophy in non-exercising mice. Regular exercise yields a multitude of systemic benefits, many of which may be mediated through the gut microbiome. ARS and University of Kentucky researchers in Lexington, Kentucky, report that cecal microbial transplants (CMTs) from exercise-trained vs. sedentary mice have modest benefits in reducing skeletal muscle atrophy in mice that were prevented from moving one back leg. Direct administration of microbial-derived compounds from an exercise-trained gut microbiome prevented muscle atrophy in the immobilized back leg. The impact of this research will be for elderly patients who suffer muscle loss when bedridden (e.g., after surgery). Further research will be needed to determine if the microbial-derived compounds can be given to humans to reduce muscle atrophy and improve outcomes.
3. Assessed the accuracy of and impacts of measuring heat stress on the eating and rumination behavior in confined cattle. Cattle subjected to elevated temperature and humidity may exhibit changes in head position and movement as well as patterns of feeding behavior, but little is known about impacts of environmental conditions on the accuracy of precision management technologies. ARS scientists at Lexington, Kentucky, in collaboration with University of Kentucky researchers, assessed the accuracy of a noseband sensor in quantifying feeding behaviors under heat stress conditions. The sensor reported both eating and rumination time with very high accuracy under both thermoneutral and heat stress conditions. This study was a first step, validating the use of this technology as a benchmark to assess impacts of heat stress on other technologies with research and/or production relevance. Additionally, this research substantiated the use of this technology for future investigations of feeding behavior in cattle subjected to heat stress and will be of interest to other researchers looking to understand and improve feeding behavior in cattle.
4. Identified a supplement that overcomes the decreased weight gain associated with fescue toxicosis in cattle. Tall fescue grass is the predominant forage in the southeast United States that contains a fungus that is beneficial to the plant by preventing overgrazing but produces toxins (ergot alkaloids) that cause fescue toxicosis in grazing livestock. A costly problem associated with fescue toxicosis is a reduction of feed intake and a decrease in weight gain. The ergot alkaloid ergovaline (primary ergot alkaloid in tall fescue) interacts with serotonin receptors and decreases circulating levels of serotonin in cattle. We have shown previously that the supplementation of the serotonin precursor 5-hydroxytryptophan can increase serotonin. ARS scientists at Lexington, Kentucky, in collaboration with University of Kentucky researchers conducted a study where cattle that were exposed to ergovaline and treated with 5-hydroxytryptophan, resulted in increased serotonin and feed intake levels compared to cattle that received ergovaline and did not receive 5-hydroxytryptophan. This is the first report of a treatment for fescue toxicosis that increases intake. Application of 5-hydroxytryptophan as a treatment for fescue toxicosis will be of interest not only to other researchers, but also to producers that graze cattle where tall fescue is the major forage.
5. Determined serotonin receptor 4 causes vasorelaxation in bovine lateral saphenous vein. Serotonin is a neurotransmitter involved in a variety of physiological functions. It is heavily involved in the regulation of vascular tone (vasoconstriction and relaxation). Livestock that graze tall fescue can be exposed to ergot alkaloid toxins that disrupt normal serotonin receptor function. There are 14 different serotonin receptors. ARS scientists at Lexington, Kentucky, in collaboration with University of Kentucky researchers characterized the relaxation caused by serotonin using isolated bovine lateral saphenous veins and selective stimulants for serotonin receptors. Serotonin can cause both contraction and relaxation in blood vessels, but serotonin- induced vasorelaxation is primarily caused by receptor subtype 4. Understanding the mechanisms of normal serotonin regulation of vascular tone will aid in the development of receptor-driven strategies to mitigate the negative impact of ergot alkaloids and this will be primarily of interest to other researchers looking to better understand how ergot alkaloids cause the negative effects seen in livestock that consume them.
6. L-DOPA attenuated the feed intake reduction caused by ergot alkaloids in cattle. Dopamine plays important roles in many biological systems and those are involved with reward sensations and energy nutrition are of interest. This is of value in livestock where control of feed intake is desired. The role of dopamine in control of feed intake is very complex and not completely understood. The dopamine precursor compound L-DOPA can be used to increase dopamine synthesis and has been shown to be effective at increasing dopamine in cattle. Ergot alkaloids are toxins that cause fescue toxicosis in grazing livestock. One of the symptoms of fescue toxicosis is decreased feed intake. ARS scientists at Lexington, Kentucky, in collaboration with University of Kentucky researchers conducted a study to determine if giving L-DOPA to cattle with fescue toxicosis would raise dopamine levels and offset some of the negative symptoms like lower feed intake. L-DOPA given to cattle did raise blood dopamine levels and did not cause any negative effects. Further, the L-DOPA treatment moderately increased feed intake in cattle with fescue toxicosis. A better understanding of intake-related problems like fescue toxicosis in grazing animals will help producers improve control of feed intake of their livestock. This research will be of interest to other researchers that study problems like fescue toxicosis in grazing animals and to producers interested in improving control of feed intake of their livestock.
Review Publications
Valente, E.L., Klotz, J.L., Markmann, R.C., Edwards, J.L., Harmon, D.L. 2024. 5-hydroxytryphophan mitigates ergot alkaloid-induced suppression of serotonin and feed intake in cattle. Journal of Animal Science. 102. Article skae083. https://doi.org/10.1093/jas/skae083.
Valente, E.L., Klotz, J.L., Markmann, R.C., Trotta, R.J., Edwards, J.L., May, J.B., Harmon, D.L. 2024. Levodopa attenuates the feed intake reduction caused by ergot alkaloids in cattle. Journal of Animal Science. 102. Article skae078. https://doi.org/10.1093/jas/skae078.
Trotta, R.J., Swanson, K.C., Klotz, J.L., Harmon, D.L. 2023. Postruminal casein infusion and exogenous glucagon-like peptide 2 administration differentially stimulate pancreatic a-amylase and small intestinal a-glucosidase activity in cattle. Journal of Nutrition. https://doi.org/10.1016/j.tjnut.2023.08.009.
Greene, M.A., Worley, G.A., Udoka, A., Powell, R.R., Bruce, T., Klotz, J.L., Bridges, Jr., W.C., Duckett, S.K. 2023. Use of agomir and antagomir technologies to alter satellite cell proliferation in vitro, mirna expression and muscle fiber hypertrophy in intrauterine growth restricted lambs. Frontiers in Molecular Biosciences. 10. Article 1286890. https://doi.org/10.3389/fmolb.2023.1286890.
Trotta, R.J., Harmon, D.L., Klotz, J.L. 2024. Serotonin receptor-mediated vasorelaxation occurs primarily through 5-HT4 activation in bovine lateral saphenous vein. Physiological Reports. 12: Article e16128. https://doi.org/10.14814/phy2.16128.
King, M.E., Herzing, H.M., McLoed, K.R., Klotz, J.L., Foote, A.P., Edwards, J.L., Harmon, D.L. 2024. Impact of endophyte-infected tall fescue seed consumption on endocrine changes associated with intake regulation and post-absorptive metabolism in growing steers. Domestic Animal Endocrinology. 89. Article 106873. https://doi.org/10.1016/j.domaniend.2024.106873.
Lakes, J.E., Ferrell, J.L., Flythe, M.D. 2023. Growth and metabolism of Clostridioides difficile in hungate-style media. Applied Microbiology. 4(1):85-95. https://doi.org/10.3390/applmicrobiol4010006.