Research Project: The Roles of Forage and Phytochemicals at the Plant-Microbe-Animal Nexus for Sustainable Ruminant

Location: Forage-animal Production Research

2023 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
Sub-objective 1.A: Investigate the interaction of serotonin and ergot alkaloid exposure to determine if serotonin can compete with ergot alkaloid (EA) at the receptor level. 80% of the myograph experiments have been completed. Early results indicate that duration of exposure to the ergot alkaloid ergovaline influences the vasoactivity of serotonin, but serotonin does not appear to alter the vasoactivity of ergovaline. It is anticipated that the remainder of necessary experiments will be completed before 2024. Sub-objective 1.B: Determination of the optimum dose of levodopa (L-DOPA), and the use of L-DOPA to mitigate the decrease of feed intake provoked by EA. Experiments have been conducted, data analyzed, and paper published. L-DOPA supplementation did successfully raise circulating dopamine levels, but this did not alter feed intake. Sub-objective 1.C: Determine the effect of leucine, glucose, and acetate infusion on mammalian target of rapamycin (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. Funds were transferred to initiate work. 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. Year one cows have been outfitted with remote sensing technology ear tags (activity, eating, rumination, etc.). Pasture (percent tall fescue, ergovaline), weather and phenotypic information are being collected. Blood samples have been collected from all cows and stored at -20 C. Samples are pending shipment to the U.S. Meat Animal Research Center for DNA genotyping. 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. Hypothesis 2A.1.: Year 1 grazing experiment is currently underway. Pasture and animal samples are pending analyses. Hypothesis 2A.3.: Year 1 of Experiment #1 is completed. All samples and data were successfully collected for year 1 and are currently undergoing analyses. 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. Lamb carcasses were collected from year 1 of Experiment #1 (completed) and year 1 of the grazing experiment (ongoing). Measurements of meat quality, carcass traits and proteome analyses are currently undergoing analyses. Sub-objective 2.C: Evaluate the impact of dietary isoflavone supplementation on the rates of antimicrobial resistance (AMR). Lamb carcasses were sampled in the abattoir using two types of media for tetracycline-resistant bacteria. Data are pending analysis. Fecal and rumen samples were obtained for quantitative polymerase chain reaction (qPCR) analysis of AMR-associated genes. Sub-objective 3.A: Investigate the impacts of pre-weaning nutritional management on microbial development, health and performance of beef calves and lambs. Hypothesis 3A.1.: Year 1 of the field experiment is complete. All cow and calf performance data, rumen, fecal, blood, and forage samples were successfully collected and are currently undergoing analyses. Hypothesis 3A.2.: Year 1 of the experiment is complete. All ewe and lamb performance data, rumen, fecal, blood, and feed samples were successfully collected and are currently undergoing analyses. 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. All preparations for the field experiment in year 2 have been completed. Heifers from both Kentucky and Montana have been selected, the ear tag based continuous remote monitoring system is installed, the experimental pastures have been prepared, and hay has been harvested. Sub-objective 3.C: Determine how ergot alkaloid exposure, grazing system, and environment influence calf microbial development, health, and performance. All preparations for the field experiment in year 2 have been completed. Heifers from both Kentucky and Montana have been selected, the ear tag based continuous remote monitoring system is installed, the experimental pastures have been prepared, and hay has been harvested. Sub-objective 3.D: Evaluation of the form of supplemental selenium to ameliorate fescue toxicosis in lactating beef cows consuming toxic endophyte-infected tall fescue (E+ TF). Funds were transferred to initiate work. Sub-objective 3.E: Manipulation of the form of supplemental selenium (Se) to increase fertility in beef cattle. Setting up the animals this year was delayed as there was insufficient time to start the animal experiment (after notification of funding). Instead, we are working on validating the proposed assays (cholesterol, cholesterol esters, high-density and low-density lipoproteins (HDL and LDL, respectively)), all the required primers sets for qPCR, and fine tuning the luteal culture methodology. Our plan is to run the animal experiment and collect all the tissues in Year 2.

Accomplishments
1. Killing tetracycline-insensitive bacteria using a natural compound from clover. It is known that animals, like soils and water, typically have some antibiotic-resistant bacteria even when there are no antibiotics present. ARS researchers in Lexington, Kentucky, fed cattle diets with increasing concentrations of cracked corn that would normally increase the numbers of antibiotic-resistant bacteria in the rumen (first “stomach”). Bacteria that could grow in the presence of the antibiotic tetracycline were counted. Cattle that received the clover compound biochanin A had up to 99.99% fewer bacteria that could resist tetracycline. This latter result is consistent with the action of biochanin A, which blocks drug efflux pumps, making some antibiotic-resistant bacteria sensitive to antibiotics again. These results support the idea that biochanin A from clover, a normal forage plant, can reduce the number of antimicrobial-resistant (AMR) bacteria in the gastrointestinal tracts of the animals.

2. Loose mineral incorporating red clover leaf prevents fescue toxicosis. Grazing endophyte-infected tall fescue (E+TF) grass pastures can persistently constrict blood vessels in animals and consequently fescue toxicosis. Pasture legumes, including red clover, contain phytochemicals (isoflavones) that reverse this effect when they are fed with contaminated fescue. However, alternative supplementation strategies have not been explored. ARS researchers in Lexington, Kentucky, determined if low levels of red clover leaf (14 – 28 g head d-1) in conventional loose mineral could mitigate fescue toxicosis symptoms. Results indicated that loose mineral containing red clover leaf prevented the adverse effects of fescue toxicosis and blood vessel constriction. Toxic endophyte-infected tall fescue grass is the most prevalent cool season grass in the United States and fescue toxicosis is thought to cost the U.S. beef industry $2 billion annually. Therefore, the application of a red clover leaf loose mineral in E+ TF grazing systems could have significant animal health and economic implications.

3. Red clover optimizes rumen fermentation and increases feed efficiency in finishing ram lambs. Red clover contains bioactive isoflavones (biochanin A) that selectively modify rumen fermentation and increase average daily gain in steers. ARS researchers in Lexington, Kentucky, along with University of Kentucky collaborators conducted an experiment to evaluate the impacts of two levels of red clover hay supplementation (7.5% and 15.0%, w/w, of the total diet) on rumen function and feed efficiency of finishing ram lambs. Adding red clover hay to high concentrate finishing diets inhibited rumen protein-wasting and promoted overall rumen fiber and starch utilization. Thus, ram lambs consuming red clover hay containing rations had increased average daily gain and reduced feed intake resulting in a 25% improvement in feed efficiency compared to control rams. Ram performance and rumen effects of red clover were consistent regardless of supplementation level in the diet. These results indicate that low levels of red clover hay can produce significant production benefits in lamb finishing systems.

4. Infusion of dopamine did not increase feed intake in cattle. The ability to improve feed intake in livestock is very desirable and can give producers the ability to improve production efficiency, because it reduces the time to reach a desired weight. Dopamine is known to influence feed intake. The dopamine precursor compound levodopa (L-DOPA) can be used to increase dopamine synthesis, but there are few studies of its effect on feed intake in cattle. ARS researchers in Lexington, Kentucky, and University of Kentucky collaborators evaluated the post-ruminal infusion of L-DOPA on circulating metabolites, energy metabolism and feed intake. The results showed that post-ruminal infusion of L-DOPA increased circulating dopamine long after L-DOPA had been cleared from the blood; however, there were no effects on other energy metabolites or feed intake. Thus, modification of dopamine does not appear to be a way to directly increase feed intake in cattle.

5. Muscle protein synthesis is not affected by ergot alkaloids in fescue toxicosis. Cattle suffering from ergot alkaloid exposure or fescue toxicosis frequently have lower rates of average daily gain (ADG). One strategy to improve the gains has been to use steroidal implants to increase ADG while on toxic tall fescue pastures. University of Kentucky researchers and ARS researchers in Lexington, Kentucky, fed cattle a fixed feed intake and different combinations of ergot alkaloid and growth promoting anabolic steroid treatments to study the effects that ergot alkaloids have on muscle protein synthesis and whether this is affected by the growth promoting implants. Muscle protein synthesis was not affected by the ergot alkaloid treatment, but it did cause a disruption in glucose and insulin clearance indicating a possible disturbance in the uptake and metabolism of glucose, the primary energy source of skeletal muscle. Steers with implants showed no effect on protein synthesis but did have decreased protein turnover and degradation that contributed to an overall accumulation of muscle protein and improved ADG. When feed intake is controlled, decreased ADG due to fescue toxicosis appears to be better explained by changes in glucose metabolism in muscle and not changes in protein synthesis. These findings indicate that future research should place more emphasis on glucose and skeletal muscle metabolism over protein synthesis to better understand decreased performance in cattle suffering from fescue toxicosis.

6. Toxins in tall fescue grass influence contraction and possibly relaxation of blood vessels. It has been previously shown that ergot alkaloids (a class of toxins) like ergovaline, which cause fescue toxicosis, cause constriction of blood vessels by interacting with receptors for the neurotransmitter serotonin in cattle and sheep. ARS researchers in Lexington, Kentucky, and University of Kentucky collaborators exposed bovine blood vessels to ergovaline for 24 hours followed by serotonin treatment or simultaneously with serotonin treatment. Results demonstrated that ergovaline exposure before serotonin treatment alters the ability of serotonin to stimulate blood vessel reaction. If ergovaline and serotonin treatments occur simultaneously, ergovaline can act as a stimulant or an inhibitor of serotonin-mediated constriction, depending on the type of blood vessel tested. In contrast, when serotonin exposure occurs after ergovaline treatment, serotonin appeared to induce relaxation of blood vessels. Understanding how complex interactions between ergovaline and serotonin occur and affect vascular function will aid in the development of solutions designed to prevent toxins like ergovaline from interacting with receptors. This could prevent or mitigate sustained vasoconstriction caused during fescue toxicosis.

Review Publications
Valente, E.E., Klotz, J.L., Egert-McLean, A.M., Costa, G.W., May, J.B., Harmon, D.L. 2023. Influence of intra-abomasal administration of L-DOPA on circulating catecholamines and feed intake in cattle. Frontiers in Animal Science. 4. Article 1127575. https://doi.org/10.3389/fanim.2023.1127575.
Klotz, J.L., MacAdam, J.W., Flythe, M.D. 2023. Editorial: Natural products in animal feed and production systems. Frontiers in Animal Science. 4. Article 1204663. https://doi.org/10.3389/fanim.2023.1204663.
Flythe, M.D., Davis, B.E., Kagan, I. 2023. Reduction in rumen tetracycline-insensitive bacteria during a grain challenge using the isoflavone biochanin A. Veterinary Sciences. 10(4). Article 273. https://doi.org/10.3390/vetsci10040273.
Sarmikasoglou, E., Ferrell, J.L., Vinyard, J.R., Flythe, M.D., Tuanyok, A., Faciola, A.P. 2022. Effects of ruminal lipopolysaccharides on growth and fermentation end products of pure cultured bacteria. Nature Scientific Reports. 12. Article 15932. https://doi.org/10.1038/s41598-022-20073-2.
Weinert-Nelson, J.R., Ely, D.G., Flythe, M.D., Hamilton, T.A., May, J.B., Ferrell, J.L., Hamilton, M.C., Jacks, W.L., Davis, B.E. 2023. Red clover supplementation modifies rumen fermentation and promotes feed efficiency in ram lambs. Journal of Animal Science. 101. Article skad036. https://doi.org/10.1093/jas/skad036.
Britt, J.L., Greene, M.A., Klotz, J.L., Justice, S.M., Powell, R.R., Noorai, R.E., Bruce, T.F., Duckett, S.K. 2022. Mycotoxin ingestion during late gestation alters placentome structure, cotyledon transcriptome, and fetal development in pregnant sheep. Human and Experimental Toxicology. 41. https://doi.org/10.1177/09603271221119177.
Trotta, R.J., Harmon, D.L., Ji, H., Klotz, J.L. 2023. Duration of ergovaline exposure influences serotonin-mediated vasoactivity of bovine mesenteric vasculature. Journal of Animal Science. 100. https://doi.org/10.1093/jas/skad100.
Ferguson, T.D., Loos, C.M., Vanzant, E.S., Urschel, K.L., Klotz, J.L., McLeod, K.M. 2023. Impact of ergot alkaloid and steroidal implant on whole-body protein turnover and expression of mTOR pathway proteins in muscle of cattle. Frontiers in Veterinary Science. 10. Article 1104361. https://doi.org/10.3389/fvets.2023.1104361.