Research Project: Understanding and Mitigating the Adverse Effects of Poisonous Plants on Livestock Production Systems

Location: Poisonous Plant Research

2020 Annual Report

Objectives
Objective 1: Develop science-based guidelines for grazing livestock on rangelands infested with toxic plants and evaluate the potential for establishing improved forage species on infested sites to improve livestock productivity, reduce the risk of livestock loss, and improve other rangeland ecosystem services. See project plan for Sub-Objectives 1.1, 1.2, 1.3, 1.4. Objective 2: Evaluate the risks of livestock losses due to variations in quantitative and qualitative differences in toxin accumulation in various plant species. See project plan for Sub-Objectives 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7. Objective 3: Enhance feed and food safety by improving risk assessment and diagnosis of plant-induced poisoning to livestock by improving analytical methods for analyzing plant and animal tissues for toxins; measuring toxicokinetics, assessing carcinogenic and genotoxic potential, and identifying toxin metabolites and biomarkers of toxicoses. See project plan for Sub-Objectives 3.1, 3.2, 3.3, 3.4. Objective 4: Develop improved procedures with guidelines for diagnostic and prognostic evaluation to reduce negative impacts of poisonous plants on livestock reproduction and embryo/fetal growth by improving early identification of poisoned animals, predicting poisoning outcomes, and management and treatment options through improved understanding of clinical, morphological and molecular alterations of plant-induced toxicoses. See project plan for Sub-Objectives 4.1, 4.2, 4.3. Objective 5: Develop guidelines to aid producers and land managers in making genetic-based herd management decisions to improve livestock performance on rangelands infested with poisonous plants through the use of animal genetics, physiological pathways, and molecular mechanisms of action that underlie the effects of toxic plants. See project plan for Sub-Objectives 5.1, 5.2.

Approach
The livestock industry in the western United States loses over $500,000,000 annually from death losses and abortions due to poisonous plants (Holechek, 2002). Actual losses due to poisonous plants are much greater due to wasted forage and increased management costs. Plant poisonings occur worldwide and include 333 million poisonous plant-infested hectares in China (Xing et al. 2001; Lu et al. 2012) and 60 million hectares in Brazil (Low, 2015). There are hundreds of genera of toxic plants representing thousands of species. The Poisonous Plant Research Laboratory (PPRL) provides numerous solutions to toxic plant problems using an integrated, interdisciplinary approach representing several scientific disciplines and continues to provide worldwide leadership in poisonous plant research to the livestock industry and consumers. The PPRL research team investigates plant poisonings in a systematic manner by identifying the plant, determining the toxin(s), evaluating the mechanisms of action, and describing the effects in animals. The ultimate goal is to develop research-based solutions to reduce livestock losses from toxic plants. There are five coordinated objectives in this project plan providing guidelines for potential scientific-based management. The project focuses on several toxic plants including larkspur, locoweed, lupine, and dehydro-pyrrolizidine alkaloid (DHPA)-containing plants utilizing the research disciplines at the PPRL. This research will reduce livestock losses from plants and enhance the economic well-being of rural communities, improve rangeland health by combating invasive plant species, and help to provide safe animal products free from potential plant toxins for consumers.

Progress Report
In support of Sub-objective 1.1, ARS scientists evaluated numerous herbicides to determine if they will aid in establishment of newly seeded grass species in revegetated rangelands infested with annual grasses that also contain populations of poisonous plants (e.g., Lupinus). Plots were established at two locations and sprayed with herbicides. The first-year evaluations occurred last summer. The second-year evaluations will occur later this summer if allowed due to maximized telework travel restrictions. Under Sub-objective 1.2, ARS scientists evaluated numerous herbicides to determine efficacy in controlling death camas and to determine if the toxicity of death camas changes due to herbicide treatment. Plots were established at two locations and sprayed with herbicides. Plots were evaluated 10 days after herbicide treatment and death camas plants were collected for chemistry analysis. The herbicides 2,4-D, Crossbow, and Plateau were effective in controlling death camas and there was no difference between the early vegetative and flowering application time. A manuscript has been submitted for publication in a peer reviewed journal. Under Sub-objective 1.3, ARS scientists collected and analyzed samples from an experiment in which alfalfa, intermediate wheat grass, and western aster were grown on selenium-contaminated soils. Additionally, samples were collected and analyzed from feeding trials in which rams were fed a high selenium-containing diet. In support of Sub-objective 2.1, ARS scientists continued research to determine the toxic larkspur alkaloid profiles from numerous, previously uncharacterized Delphinium species. Methyllycaconitine, the larkspur toxin most commonly associated with poisoning of cattle, was detected in most species with varying ratios of the toxic to non-toxic-type alkaloids. Under Sub-objective 2.2, ARS scientists surveyed several Astragalus species for selenium. Selenium was detected in several species. In support of Sub-objective 3.2, ARS scientists identified the major diterpene acids in broom snakeweed, and the common metabolites found in serum of animals fed broom snakeweed. Work has been completed on defining the chemotypes in two broom snakeweed species. Samples have been collected throughout Wyoming, Colorado, Texas, New Mexico and Utah. Plants were taxonomically identified and then classified into eight different chemotypes based on the diterpene acid profiles. The completed structural identities of 21 diterpene acids isolated from the two broom snakeweed species has been completed. A publication has been submitted and is under review. Under Sub-objective 3.3, ARS scientists characterized and compared the serum mannosidase activity and sensitivity to the toxin swainsonine in horses, cows, goats, and sheep. Under Sub-objective 3.4, ARS scientists evaluated riddelliine in P53 knockout mice. A detailed examination for cancer-type lesions has been performed. Approximately 40% of the mice were euthanized early and several had hepatic and other tissue neoplastic diseases. In support of Sub-objective 4.2, ARS scientists determined that the plant Salvia reflexa contains hepatotoxic compounds. One publication describing the case history of poisoning by Salvia-contaminated hay has been submitted for publication in a peer reviewed journal. A second publication on chemical identification of the toxins is being prepared. Under Sub-objective 4.3, ARS scientists analyzed samples from animals fed high selenium containing diets and are working on the histology analyses of the samples. In support of Sub-objective 5.2, ARS scientists continue to determine the susceptibility, or resistance, of cattle to larkspur poisoning. Susceptible and resistant cows and heifers were inseminated with semen from similarly responding bulls. After maximum telework concludes, the calves will be evaluated to determine their susceptibility to larkspur.

Accomplishments
1. Analysis of rumen contents and ocular fluid for toxic alkaloids from goats and cows dosed with larkspur, lupine, and death camas. Larkspurs, lupines, and death camas can be acutely toxic to livestock and are serious poisonous plant problems in western North America. ARS scientists in Logan, Utah, treated goats and cows with sub-lethal amounts of larkspur, lupine, and death camas. Rumen contents and ocular fluid samples were collected from these animals, and analytical methods were developed for the detection of toxic alkaloids in these samples. The toxins were detected in the rumen contents and ocular fluid samples from the goats and cows dosed with larkspur, lupine, and death camas. In addition, results from a case report where rumen contents were analyzed from a cow that was suspected to have died due to larkspur was reported. This demonstrates the utility of the methods described for the diagnosis of acute plant poisonings and will be valuable information for extension agents and veterinarians, especially diagnostic laboratories to aid in the diagnosis of poisoned animals, as well as livestock producers.

2. Evaluation of earwax, hair, oral fluid, and nasal mucus as noninvasive specimens to determine livestock exposure to poisonous plants. Poisoning of livestock by plants often goes undiagnosed because there is a lack of appropriate or available specimens for analysis. ARS researchers at Logan, Utah, detected larkspur alkaloids in the earwax, hair, oral fluid, and nasal mucus in cattle that were administered single doses of several species of larkspur plants. Lupine alkaloids were detected in the earwax, hair, oral fluid, and nasal mucus in cattle that were administered a single dose of lupine plants. In addition, alkaloids from lupine were detected in the earwax of cattle that had grazed in lupine-infested rangelands. The advantage of using earwax, hair, oral fluid, and nasal mucus for chemical analysis is that these biological specimens are noninvasive and are simple to collect, no special equipment is required, and untrained personnel can easily collect the samples for analysis.

3. Comparison of the geographical and seasonal variation in the toxins in foothill death camas plants. Death camas is a common poisonous plant in North America with plants occurring in a wide variety of habitats with species of toxic concern occurring primarily in meadows, grasslands, shrublands, and mountains. ARS scientists in Logan, Utah, compared the concentration of the known toxins in death camas in the different plant parts, over the growing season and across several locations. The results suggest that the toxic risk associated with death camas is greatest in the early vegetative growth stages followed by the flower and pod stages. There is a toxic risk to livestock as long as the plant is present, and caution should be taken when grazing livestock in areas with death camas as long as the plant is green. A similar toxic risk was observed in all locations evaluated. This information will be helpful to extension agents and range scientists at the various government agencies, as well as livestock producers.

4. Comparison of the geographical and seasonal variation in the toxins in water hemlock plants. Water hemlock is one of the most toxic plants in North America. ARS scientists at Logan, Utah, compared the variation in the toxic compounds in the different plant parts and water hemlock populations across western North America. There is a difference in the amount of the toxins in different plant parts, with the tubers from water hemlock being the most significant risk to poison livestock. The results also suggest that although there is variation in toxin concentration from location to location, all water hemlock populations across western North American likely pose a similar poisoning risk to livestock. This information will be helpful to extension agents and range scientists at the various government agencies, as well as livestock producers.

5. Comparison of Astragalus lentiginosus and Ipomoea carnea poisoning in goats. The toxin swainsonine, found in some Astragalus and Oxytropis (i.e., locoweed) species, is a potent cellular toxin that often poisons many livestock throughout the world every year. Other toxic plant genera, such as some Ipomoea species, also contain swainsonine as well as calystegines which are similar toxic alkaloids. The toxicity of calystegines is poorly characterized. ARS scientists in Logan, Utah, directly compared A. lentiginosus and I. carnea poisoning in goats to better characterize the role of the calystegines. The findings suggest that I. carnea-induced clinical signs and lesions are due to swainsonine and that calystegines contribute little, or nothing, to toxicity in goats in the presence of swainsonine. Understanding the contribution of different active compounds to toxicity aids in diagnosis. This information will be helpful to veterinarians, extension agents and range scientists at the various government agencies, as well as livestock producers.

6. Evaluation of the lethality/toxicity of water hemlock in goats. Water hemlock is one of the most toxic plants to livestock and humans. However, little is known regarding the amount of plant required to cause death. ARS investigators in Logan, Utah, determined the amount of water hemlock needed to kill a goat. The results from this study suggest that 1–2 fresh tubers would be lethal to goats, which is consistent with case reports of human poisonings. This information is useful as it provides a relative risk assessment of the plant. This information will be helpful to veterinarians, extension agents and range scientists at the various government agencies, as well as livestock producers.

7. The toxicity of Isocoma plant species was determined in cattle. Isocoma plant species often cause significant livestock losses in the southwestern United States. The toxicity of different Isocoma species in cattle has not been previously determined. ARS researchers at Logan, Utah, compared the relative toxicity of different Isocoma species while also determining the concentrations of the putative toxins in the plant material. This information is valuable for land managers, veterinarians and extension agents when determining the risk associated with grazing certain rangelands and when diagnosing potential cases of poisoning by Isocoma species.

8. Comparative process to evaluate toxicity of riddelliine in primary mouse, rat and chick hepatocytes developed. Dehydropyrrolizidine alkaloid (DHPA) producing plants commonly poison livestock, wildlife and humans. Poisoning occurs when DHPAs are ingested as feed or food, or when they contaminate medicinal or herbal products. Direct toxicologic comparison of individual DHPAs is essential to estimate their actual health risks, but this has been problematic due to varying models and difficulties in DHPA isolation or synthesis. ARS scientists in Logan, Utah, characterized the effect of riddelliine, a common DPHA, on primary mouse, rat, and chick hepatocyte cultures, with the aim of developing a suitable, sensitive model for assessing DHPA-related cytotoxicity. This model may be useful to directly compare panels of DHPAs, including rare or difficult to isolate alkaloids. This information will valuable for scientists studying DHPAs, extension agents and veterinarians at diagnostic laboratories.

9. Characterization of the development of tolerance of cattle to larkspur poisoning. The severity of larkspur poisoning depends on the genetic background of the cattle, the amount of plant consumed, the rate of consumption, and the concentrations of toxic alkaloids in the plants. Identifying cattle which are naturally resistant to larkspur intoxication would improve grazing animal welfare on these rangelands and reduce losses to poisonous plants. ARS researchers at Logan, Utah, have identified and characterized the development of tolerance to larkspur alkaloids by the cattle. This information will be useful for scientists studying larkspur toxicosis as well as land managers, extension agents, and livestock producers.

10. Evaluation of the toxic principle found in white snakeroot and rayless goldenrod in cell culture models. Tremetone is a putative toxin in white snakeroot and rayless goldenrod. ARS scientists in Logan, Utah, tested the actions of these toxins in two different cell lines. Tremetone did not require activation to be toxic to the cells. This suggests that tremetone is directly toxic without metabolism. This work helps in the understanding of the mechanism by which white snakeroot and rayless goldenrod are toxic to animals, which will aid in the development of therapies for poisoned animals.

11. Analysis of Convolvulaceous (morning glory) species for bioactive alkaloids that cause poisoning. Some Convolvulaceous species have been reported to contain several bioactive principles that are toxic including swainsonine, ergot alkaloids, and indole diterpene alkaloids. ARS researchers at Logan, Utah, analyzed thirty Convolvulaceous species for these alkaloids. The ergot alkaloids were detected in 18 species, the indole diterpenes were detected in 10 species, and swainsonine was detected in two species. The data suggested that there was an association between the occurrence of the respective bioactive principle and the genetic relatedness of the respective host plant species. This information provides a reference list of potentially toxic species and provides a better understanding of the composition of bioactive principles in some Convolvulaceous species.

12. An evaluation of the susceptibility of goats to larkspur poisoning. Larkspurs are a major cause of cattle losses in western North America, whereas sheep have been shown to be resistant to larkspur toxicosis. Goats are often used as a small ruminant model to study poisonous plants, even though they can be more resistant to some poisonous plants. It is not known how susceptible goats are to the adverse effects of larkspurs. ARS scientists in Logan, Utah, evaluated the susceptibility of goats to larkspur poisoning. None of the goats treated in this study, exhibited clinical signs typical of larkspur poisoning. We conclude that goats are resistant to larkspur toxicosis, and thus it is very unlikely that goats would be poisoned by larkspur.

13. Detection of swainsonine-producing endophytes in South American Astragalus species. Swainsonine, a toxic indolizidine alkaloid, has been detected in several South American Astragalus species. ARS researchers in Logan, Utah, in collaboration with colleagues from Argentina, investigated several swainsonine-containing species for the presence of a fungal symbiont. A fungal symbiont, Alternaria section Undifilum, was detected by both culturing techniques and PCR in species containing swainsonine and was found to produce swainsonine. This is important information that is valuable to scientists studying plants that contain swainsonine, which includes the locoweeds found throughout the United States.

Review Publications
Stegelmeier, B.L., Jones, M., Womack, C.P., Davis, T.Z., Gardner, D.R. 2019. North American hard yellow liver disease: an old problem readdressed. Poisonous Plant Research. 2:1-13. https://doi.org/10.26077/6ksg-1685.
Carvalho Nunes, L., Stegelmeier, B.L., Cook, D., Pfister, J.A., Gardner, D.R., Riet-Correa, F., Welch, K.D. 2019. Clinical and pathological comparison of Astragalus lentiginosus and Ipomoea carnea poisoning in goats. Toxicon. 171:20-28. https://doi.org/10.1016/j.toxicon.2019.09.016.
Green, B.T., Lee, S.T., Davis, T.Z., Welch, K.D. 2019. Microsomal activation, and SH-SY5Y cell toxicity studies of tremetone and 6-hydroxytremetone isolated from rayless goldenrod Isocoma pluriflora and white snakeroot Agertina altissima, respectively. Toxicon: X. 5. https://doi.org/10.1016/j.toxcx.2019.100018.
Green, B.T., Pfister, J.A., Gardner, D.R., Welch, K.D., Cook, D. 2020. Dynamics of larkspur (Delphinium barbeyi) pellet consumption and tolerance of the inhibitory effects of larkspur alkaloids on muscle function in cattle. Poisonous Plant Research. 3:28-41. https://doi.org/10.26077/zsrd-d783.
Green, B.T., Gardner, D.R., Stonecipher, C.A., Lee, S.T., Pfister, J.A., Welch, K.D., Cook, D., Davis, T.Z., Stegelmeier, B.L. 2020. Larkspur poisoning of cattle: plant and animal factors that influence plant toxicity. Rangelands. 42(1):1-8. https://doi.org/10.1016/j.rala.2020.01.004.
Davis, T.Z., Green, B.T., Stegelmeier, B.L., Lee, S.T. 2020. The comparative toxicity of Isocoma species in calves. Toxicon: X. 5. https://doi.org/10.1016/j.toxcx.2019.100022.
Stonecipher, C.A., Welch, K.D., Lee, S.T., Cook, D., Pfister, J.A. 2020. Geographical and seasonal variation in water hemlock (Cicuta maculata) toxins. Biochemical Systematics and Ecology. 89. https://doi.org/10.1016/j.bse.2020.104012.
Welch, K.D., Stonecipher, C.A., Gardner, D.R., Green, B.T., Cook, D. 2020. An evaluation of the susceptibility of goats to larkspur toxicosis. Poisonous Plant Research. 3:19-27. https://doi.org/10.26077/y7pp-q806.
Pessoa, D.A., Lopes, J.R., Souza, E.M., Campos, E.M., Medeiros, R.M., Cook, D., Lee, S.T., Riet-Correa, F. 2019. Herbaspirillum seropedicae as a degrading bacterium of monofluoracetate: effects of its inoculation in goats by ingesting Amorimia septentrionalis and the concentrations of this compound in plants sprayed with the bacterium. Pesquisa Veterinaria Brasileira. 39(10):802-806. https://doi.org/10.1590/1678-5150-pvb-6305.
Stonecipher, C.A., Cook, D., Welch, K.D., Gardner, D.R., Pfister, J.A. 2020. Seasonal variation in toxic steroidal alkaloids of foothill death camas (Zigadenus paniculatus). Biochemical Systematics and Ecology. 90. https://doi.org/10.1016/j.bse.2020.104044.
Welch, K.D., Stonecipher, C.A., Lee, S.T., Cook, D. 2020. The acute toxicity of water hemlock (Cicuta douglasii) in a goat model. Toxicon. 176:55-58. https://doi.org/10.1016/j.toxicon.2020.02.010.
Lee, S.T., Welch, K.D., Stonecipher, C.A., Cook, D., Gardner, D.R., Pfister, J.A. 2020. Analysis of rumen contents and ocular fluid for toxic alkaloids from goats and cows dosed larkspur (Delphinium berbeyi), lupine (Lupinus leucophyllus), and death camas (Zigadenus paniculatus). Toxicon. 176: 21-29. https://doi.org/10.1016/j.toxicon.2020.01.003.
Marin, R.E., Micheloud, J.F., Vignale, N.D., Gimeno, E.J., O'Toole, D., Gardner, D.R., Woods, L., Uzal, F.A. 2020. Intoxication by Astragalus garbancillo var. garbancillo in llamas. Journal of Veterinary Diagnostic Investigation. 32(3):467-470. https://doi.org/10.1177/1040638720914338.
Neyaz, M., Cook, D., Creamer, R. 2020. Molecular differentiation of Astragalus species and varieties from the Western United States: the chloroplast DNA bridge between evolution and molecular systematics. Poisonous Plant Research. 3:1-18. https://doi.org/10.26077/6vtc-b962.
Stonecipher, C.A., Lee, S.T., Green, B.T., Cook, D., Welch, K.D., Pfister, J.A., Gardner, D.R. 2019. Evaluation of noninvasive specimens to diagnose livestock exposure to toxic larkspur (Delphinium spp.). Toxicon. 161:33-39. https://doi.org/10.1016/j.toxicon.2019.02.013.
Heiling, J.M., Cook, D., Lee, S.T., Irwin, R.E. 2019. Pollen and vegetative secondary chemistry of three pollen-rewarding lupines. American Journal of Botany. 106(5):643–655. https://doi.org/10.1002/ajb2.1283.
Mendonca, F.S., Siva Filho, G.B., Chaves, H.A., Aires, L.D., Braga, T.C., Gardner, D.R., Cook, D., Buril, M.T. 2018. Detection of swainsonine and calystegines in Convolvulaceae species from the semiarid region of Pernambuco. Pesquisa Veterinaria Brasileira. 38(11):2044-2051. http://doi.org/10.1590/1678-5150-PVB-5945.
Cook, D., Lee, S.T., Panaccione, D.G., Leadmon, C.E., Clay, K., Gardner, D.R. 2019. Biodiversity of Convolvulaceous species that contain ergot alkaloids, indole diterpene alkaloids, and swainsonine. Biochemical Systematics and Ecology. 86. https://doi.org/10.1016/j.bse.2019.103921.
Stegelmeier, B.L., Reseager, W.S., Colegate, S.W. 2020. The comparative cytotoxicity of riddelliine in primary mouse, rat, and chick hepatocytes. Poisonous Plant Research. 3:43-57. https://doi.org/10.26077/p9te-bv07.
Martinez, A., Robles, C., Roper, J.M., Gardner, D.R., Neyaz, M., Joelson, N., Cook, D. 2019. Detection of swainsonine-producing endophytes in Patagonian Astragalus species. Toxicon. 117:1-6. https://doi.org/10.1016/j.toxicon.2019.09.020.
Vikuk, V., Young, C.A., Lee, S.T., Nagabhyru, P., Krischke, M., Mueller, M.J., Krauss, J. 2019. Infection rates and alkaloid patterns of different grass species with systemic Epicloë endophytes. Applied and Environmental Microbiology. 85(17). https://doi.org/10.1128/AEM.00465-19.
Spackman, C., Monaco, T.A., Stonecipher, C.A., Villalba, J.J. 2020. Plant silicon as a factor in Medusahead (Taeniatherum caput-medusae) invasion. Invasive Plant Science and Management. 13(3):143-154. https://doi.org/10.1017/inp.2020.20.
Salinas, L.M., Balseiro, A., Jiron, W., Peralta, A., Munoz, D., Fajardo, J., Gayo, E., Martinez, I.Z., Riet-Correa, F., Gardner, D.R., Marin, J.F. 2019. Neurological syndrome in goats associated with Ipomoea trifida and Ipomoea carnea containing calystegines. Toxicon. 157:8-11. https://doi.org/10.1016/j.toxicon.2018.11.291.
Gardner, D.R., Cook, D., Larsen, S.W., Stonecipher, C.A., Johnson, R. 2020. Diterpenoids from Gutierrezia sarothrae and G. microcephala: chemical diversity, chemophenetics and implications to toxicity in grazing livestock. Phytochemistry. 178. https://doi.org/10.1016/j.phytochem.2020.112465.
Buroni, F., Gardner, D.R., Boabaid, F.M., Oliveira, L.G., De Nava, G., Lopez, F., Riet-Correa, F. 2020. Spontaneous abortion in cattle after consumption of Hesperocyparis (Cupressus) macrocarpa (Hartw.) Bartel and Cupressus arizonica (Greene) needles in Uruguay. Toxicon. 181:53-56. https://doi.org/10.1016/j.toxicon.2020.04.104.
Stonecipher, C.A., Ransom, C., Thacker, E., Welch, K.D. 2020. Herbicide control of broom snakeweed (Gutierrizia sarothrae). Poisonous Plant Research. 3:74-81. https://doi.org/10.26077/ze5v-af64.
Pfister, J.A., Cook, D., Lee, S.T., Gardner, D.R., Riet-Correa, F. 2020. Livestock preference for endophyte-infected or endophyte-free Oxytropis sericea, Ipomoea carnea, and Ipomoea asarifolia. Poisonous Plant Research. 3:58-73. https://doi.org/10.26077/8h4g-v983.