Location: Poisonous Plant Research2013 Annual Report
Objective 1: Develop science-based guidelines for grazing livestock on rangelands infested with toxic plants (particularly Lupinus, Senecio, Delphinium and swainsonine and selenium-containing plants) and evaluate the potential for establishing improved forage species on infested sites to improve livestock gains, reduce the risk of livestock loss, and improve other rangeland ecosystem services. Objective 2: Reduce the risks of livestock losses due to variations in quantitative and qualitative differences in toxin accumulation over time and plant species by quantifying the influence of endophytes, climate changes, and genotype on plant toxin accumulation (particularly swainsonine-containing plants and Delphinium and Lupinus species). 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. 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 toxicosis. Objective 5: Develop guidelines to aid producers and land managers in making genetic-based herd management decisions to improve livestock performance and safety on grazed rangelands infested with poisonous plants through the use of identified animal genes, physiological pathways, and molecular mechanisms of action that underlie Conium, Cicuta, Delphinium, Lupinus, and Nicotiana, and other neurotoxic plant effects.
Livestock poisoning by plants results in over $503,000,000 lost to the livestock industry annually in the 17 western United States from death losses and abortions alone (Holechek, 2002). Plant poisonings extend worldwide to include 333 million poisonous plant-infested hectares in China and 60 million hectares in the central western region of Brazil, to name a few. There are over 6,000 species of pyrrolizidine alkaloid (PA)-containing plants, and over 350 individual PAs causing diseases in animals and humans have been identified. Economic losses are much larger as significant amounts of nutritious forage are wasted and management costs are increased due to the threat of toxic plant-related livestock losses. The Poisonous Plant Research Laboratory (PPRL) has provided worldwide leadership in poisonous plant research to the livestock industry and consumers including numerous solutions to toxic plant problems using an integrated, interdisciplinary approach (see Figure below). The research team investigates plant poisonings in a systematic matter by identifying the plant, describing the effects in animals, determining the toxin(s) and evaluating the mechanisms of action. 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 genetic-based management. 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.
Losses to livestock producers continue to plague the industry reducing the economic viability of rural ranching communities. ARS researchers at the Poisonous Plant Research Lab in Logan, UT continue to mitigate losses through team research using an integrated, interdisciplinary approach. Five coordinated objectives have been defined to develop research based solutions to reduce livestock losses from poisonous plants. Research progress over the last year include establishment of seeding plots using introduced grass and forb species to improve rangeland conditions and provide alternative high quality forages for livestock to reduce grazing of poisonous plants. An endophyte (Undifillum) was shown to produce the locoweed toxin swainsonine. In the last year similar endophytes that produce swainsonine have been discovered in other plant species including Ipomoea in Brazil, Swainsona in Australia and Sida and Turbina in Africa and South America. Breed and individual animal to animal variation in response to larkspur poisoning suggests a genetic basis for these differences and 5 breeds of cattle have now been screened. Juniper species have been shown to cause abortion in cattle and chemical analysis of juniper collections in Oregon demonstrated that the toxin (isocupressic acid) was the same as that found in Ponderosa pine needles. Pyrrolizidine alkaloids poison animals and people throughout the world. Research screening individual PA’s through cell culture methods and using a cancer P53 transgenic mouse model has provided new information on mechanism and structure activity relationship of selected PA’s. Over 15 benzofuran ketones have been identified in white snakeroot and rayless goldenrod and the toxicity and role of each ketone is being evaluated in a Spanish goat small ruminant model. Plants that accumulate selenium have been evaluated for the chemical form, concentration of selenium in plant parts and the effect of different chemical forms on toxicity in sheep, cattle and horses.
1. Rangeland restoration to reduce losses to livestock from poisonous plants. ARS researchers at Logan, UT established seeding and demonstration plots using improved rangeland grasses and forbs to demonstrate that restoration of rangelands to a healthy ecosystem will reduce or prevent losses from poisonous plants. Replicated seeding plots and larger demonstration plots were established on the Channeled Scablands in eastern Washington State where lupine-induced “crooked calf syndrome” is endemic and occasional catastrophic losses occur. Evaluation of replicated plots and demonstration plots indicated that varieties of wheat grasses including Hycrest and Siberian, mixed with palatable forbs such as forage Kochia, will establish and persist in this harsh environment. Seeding plots have been evaluated over two years including biomass and nutrient value. This research is important to ranchers over the 2000 square mile rangeland called the Channeled Scablands and will improve forage quality, biomass and reduce losses from lupine-induced crooked calf syndrome.
2. Analysis of pyrrolizidine alkaloid (PA) in contaminated feeds. Pyrrolizidine alkaloid (PA)-containing plants have global distribution, and they often poison animals and humans by contaminating pastures, feeds, food, herbal products, and medicinal products. Toxicity is characterized by liver failure; several PAs are also carcinogenic. ARS scientists in Logan, UT developed in vitro and in vivo models of poisoning including a transgenic mouse model of carcinogenesis and confirmed that several PA are carcinogenic. This research explains a disease called “Unidentified Liver Disease” in poor populations in the northwest region of Tigray, Ethiopia and it is suspected that the disease is related to natural toxins in food. In cooperation with the Centers for Disease Control and Prevention, samples were collected and screened from the Tigray region of Ethiopia, including millet, teff, sorghum, maize, sesame, honey and an alcoholic drink called tella. Samples were analyzed by ARS scientists in Logan, UT for the presence of toxic PA’s which will cause liver disease. Because PA-containing plants are worldwide in distribution and impact, this research is important to national and international animal and human health organizations.
3. Poisoning in livestock by plants that accumulate selenium. Selenium is an essential micronutrient in the diet of animals and people. ARS researchers in Logan, UT, determined the blood profiles of various seleno-compounds in sheep and cattle. Pathology in poisoned animals was described and characterized based on the different types of selenium. The elimination of selenium following exposure to high Se levels in plants is slow requiring a relatively long period for selenium to clear from the animal’s system. Additionally, high levels of selenium in the diet of sheep suppressed reproductive performance. This research is important to assess risk on ranges and reclamation sites where soils are high in selenium.
4. Diagnosis of pine needle and juniper induced abortions. Sera samples from aborted fetuses and their damns were analyzed for metabolites of isocupressic acid (ICA), the abortifacient toxin in pine needles. In a number of cases diagnostic metabolites were detected and established cause of premature parturition or abortion. In particular ARS scientists in Logan, UT established that common juniper was the cause of plant induced abortion in the Rioja mountain region of Spain. This research is important to cattle producers in the western U.S. and Spain and identified the cause of cattle abortions from juniper.
5. Identification of swainsonine producing endophytes in Swainsona canescens. Legumes belonging to the Astragalus, Oxytropis and Swainsona genera cause livestock poisoning in the Americas (locoism), Asia (locoism) and Australia (peastruck). The toxin in S. canescens is swainsonine, and was shown to be produced by a fungus related to the Undifilum found in Astragalus and Oxytropis. The fungus cultured from S. canescens was shown to produce swainsonine in vitro and represents a new species of Undifilum and has significant importance to solving the problem of livestock poisoning in the U.S., Asia and Australia.
6. Genetic predisposition to larkspur poisoning in cattle. ARS Scientists at Logan, UT have conducted research on breed differences for susceptibility to larkspur poisoning. Five breeds have been tested thus far and while there are significant breed differences there are also differences between individuals within each breed. The number of larkspur sensitive animals may vary in each individual herd/breed due to the genetic background of that herd/breed. These differences are likely due to each individual animal’s genetic predisposition for larkspur poisoning which could potentially be predicted from its DNA sequence. We intend to exploit this variation between breeds and individuals within breeds to eventually provide a gene based method to select animals with resistance to larkspur poisoning and other neurological plant toxins to ultimately reduce or prevent cattle losses to larkspur.
7. Common Juniper trees contain the pine needle abortion toxin ICA. Surveys of western juniper trees across the state of Oregon demonstrated that western juniper trees will cause late-term abortions in cattle, similar to ponderosa pine trees. The risk is not well characterized and it is unclear how much variation there is in the abortifacient compounds in western juniper trees. Thus, ARS researchers in Logan, UT collected samples of bark, needles, and berries from western juniper trees from 35 locations across the state of Oregon in order to determine the variation in abortifacient compounds in western juniper trees. Results indicated that western juniper trees throughout the state of Oregon should be considered a risk to induce late-term abortions in cattle. This knowledge will allow livestock owners and others to better understand the potential abortion risk from western juniper trees.
8. Selenium (Se)-containing plants are reputed to be unpalatable to livestock. A study was conducted by ARS Scientists to determine if sheep and cattle could discriminate between forages and feeds with different concentrations of Se. Initially, freshly-harvested forages (intermediate wheatgrass, Thinopyrum intermedium; alfalfa, Medicago sativa; western aster, Symphyotrichum ascendens) with different Se concentrations were offered to cattle and sheep in preference trials. The Se concentrations ranged from 0.8 to 50 parts per million (ppm) in grass, 1.4 to 275 ppm in alfalfa, and 4 to 4,455 ppm in aster. The Se concentration had no influence on the initial or subsequent preferences of sheep or cattle for grass or alfalfa. Cattle developed an aversion to aster after consuming 95% of the offered plant material during the first brief exposure, and subsequently refused to eat any aster plants. Sheep consumption of aster was variable, but their preference was not driven by Se concentration. After initial exposure, cattle may have generalized an aversion based on shared flavors in the low- and high- Se asters. In the second trial, cattle and sheep were offered pellets containing various concentrations of Se. A trial with pellets was conducted using concentrations of 0, 5, 25, 45, 110 ppm Se. When given Se pellets, initial responses were variable, but animals adjusted their intake over time to allow for detoxification when over ingesting Se. A more thorough understanding of diet selection as a function of selenium concentration will provide information to land managers and stakeholders about the risk associated with selenium containing forage.
9. Understanding the metabolism and toxicity of pyrrolizidine alkaloids (PA’s) in fireweed. Fireweed (Senecio madagascariensis) is an invasive weed on the island of Hawaii that causes liver disease in cattle and results in large losses because of liver condemnation at the slaughter plants. ARS scientists from Logan, UT in collaboration with scientists from the U. of Hawaii isolated and characterized a mixture of PA’s from fireweed and determined how much ingested plant would result in toxicoses. Synthesis of PA adducts and their pyrrole metabolites were completed for future research. Detection and identification of PA metabolites in the liver of diseased animals is an important diagnostic tool for all diagnostic labs in the U.S. This research impacts the international scientific community also and resulted in collaborations between PPRL and the Institute for Risk Assessment in Germany to validate and screen for PA’s in other food products consumed by animals and people.
10. Identification of swainsonine-producing endophytes in other plant species. Some plant species within the Convolvulaceae (morning glory family) from South America, Africa, and Australia cause a neurologic disease in grazing livestock similar to locoweed poisoning in the western U.S. The morning glory plant, Ipomoea carnea, contains the toxins swainsonine and calystegines, inhibitors of key enzymes in protein metabolism. Swainsonine, the locoweed toxin, has been shown to be produced by a fungus that grows within the Astragalus and Oxytropis genera, and causes a neurologic disease in grazing livestock called locoism. Research by ARS scientists in Logan, Utah determined that the swainsonine producing fungus was detected in I. carnea by cell culture methods and PCR. It was also determined that plants derived from fungicide-treated seeds did not produce swainsonine. This research impacts livestock production systems in the western U.S. as well as large agricultural areas in South America, Africa and Australia.
11. Determining seed germination rates in seleniferous soils. Historical reclaimed mine sites contain high concentrations of selenium making it difficult to establish and maintain forages safe for grazing when they are reclaimed. Seeds of eleven different plant species were germinated in seleniferous soils containing 16, 35 and 70 ppm Se. ARS researchers in Logan, UT determined that there were no differences in germination rates of the different plant species in soils containing 16, 35 ppm Se. However, in soils containing 70 ppm Se there were differences as the mean rate of seedling emergence were highest in the intermediate wheat grass > Russian Wildrye > big bluegrass > Siberian wheat grass > prairie junegrass > mountain brome > western wheat grass> slender wheat grass > meadow brome > western aster > tufted hairgrass. This information will be helpful in determining forages that will establish in seleniferous soils commonly found on old phosphate mine sites and provide safe forage for livestock and wildlife.
12. White snakeroot and rayless goldenrod poisoning in livestock. White snakeroot (Ageratina altissima var. altissima) and rayless goldenrod (Isocoma pluriflora) are common North American plants that contain potent toxins that poison livestock and people. ARS scientists in Logan, UT identified and characterized these toxins as benzofuran ketones. Methods to detect low concentrations of these toxins in plants, feed, and animal tissues were developed. Research trials were completed to determine which chemical fractions contained the most bioactive compounds. This information will be used by livestock producers, veterinarians, diagnosticians, and human health scientists across the U.S. to monitor feeds and food for contamination, diagnose poisoning, and better predict the prognosis of poisoned animals. This research is essential to evaluate risk for livestock producers and veterinarians to identify and avoid exposure to toxic populations of white snakeroot and rayless goldenrod.
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