Location: Poisonous Plant Research2019 Annual Report
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.
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.
This is a new project which began in February 2019. This project continues research from a bridging project 2080-32630-013-00D. Under Sub-objective 1.1, ARS scientists at Logan, Utah, evaluated 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 will occur later this summer. Under Sub-objective 1.2, the scientists evaluated herbicides to determine efficacy in controlling death camas, and 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 chemical analysis. Under Sub-objective 1.3, ARS scientists conducted greenhouse studies to grow western aster, alfalfa, and intermediate wheat grass in seleniferous soils from contaminated phosphate mine sites. Amendments were added to the soil and the addition of zero valent iron decreased the uptake of selenium in each of the forages. Under Sub-objective 2.1, ARS scientists initiated research to determine norditerpene alkaloid profiles from numerous, previously uncharacterized Delphinium species. Methyllycaconitine, a primary larkspur toxin, 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 other Astragalus species for swainsonine. Swainsonine was not detected in any of the additional species surveyed. Under Sub-objective 2.5, the ARS scientists collected water hemlock plants from six different geographical locations in the western U.S. at the various phenological growth stages. The plant samples have been processed and chemically evaluated for cicutoxin concentrations. Under Sub-objective 2.6, ARS scientists collected death camas plants from two different geographical locations in the western USA at the various phenological growth stages. The plant samples have been processed and chemically evaluated for zygacine concentrations. Additionally, under this objective ARS scientists at Logan, Utah initiated a multi-year study in 2011 to measure plant density and life history of Delphinium andersonii populations in southern Idaho. In five of nine years, essentially no plants emerged and flowered because of drought conditions. During the four years when some plants emerged and flowered, plant densities were high enough to pose a serious threat to grazing cattle. Approximately 10 percent of the marked plants remained dormant for two to four years, then emerged when precipitation was favorable. Understanding the life history and weather conditions that promote Delphinium andersonii populations will enable livestock producers to better manage risk of cattle deaths. Under Sub-objective 3.1, ARS scientists initiated studies to evaluate several types of animal tissues/specimens, such as ear wax, nasal mucous and saliva, as potential matrices for the detection of exposure to poisonous plants, including: larkspur, lupine, death camas, and water hemlock. Under Sub-objective 3.2, ARS scientists continued research on the isolation and identification of potential toxins from broom snakeweed that may cause abortion in cattle. Plants have been collected, with most of the potential toxins isolated and identified from the major plants. Plants are now being classified by geographic location, species, and chemical types. Under Sub-objective 3.3, the scientists made progress evaluating serum mannosidase activity and sensitivity to swainsonine in horses, cows, goats and sheep. Under Sub-objective 3.4, the scientists established a mouse breeding colony of P53 knockout mice to be used in determining the carcinogenic potential of pyrrolizidine alkaloids. Over 150 heterozygous male mice have been dosed with control material, riddelliine and lasiocarpine and the mice are being monitored for cancer development. Under Sub-Objective 4.2, the ARS scientists continued research on the identification of the toxins in Salvia plants using bioassay-guided isolation of the toxic compounds. Under Sub-objective 4.3, the scientists fed male sheep (rams) with high selenium (Se) feeds for 12 weeks. When rams were fed greater than 10 parts per million (ppm) Se feed spermatogenesis was negatively impacted. There was a decrease in the percentage of progressively motile sperm and an increase in abnormal sperm. Additionally, under Objective 4, Convolvulaceous species have been reported to contain several bioactive principles thought to be toxic to livestock including the calystegines, swainsonine, ergot alkaloids, and indole diterpene alkaloids. To further explore the biodiversity of species that may contain indole diterpenes, ARS scientists analyzed several Convolvulaceous species (n=30) for indole diterpene alkaloids, representing four genera, Argyreia, Ipomoea, Stictocardia, and Turbina, that had been previously reported to contain ergot alkaloids. Ergot alkaloids were detected in 18 species representing all four genera screened. Indole diterpenes were detected in two Argyreia species and eight Ipomoea species, of the 18 that contained ergot alkaloids. Swainsonine was detected in two Ipomoea species. Additionally, under Objective 4, ARS scientists determined goat, sheep, and cattle preferences for endophyte positive or endophyte negative Oxytropis sericea, Ipomoea carnea, and Ipomoea asarifolia. Goats and sheep rejected all forage choices regardless of endophyte status, except for grass and alfalfa hay. Endophyte status had no influence on cattle forage preferences. Cattle rejected all Oxytropis sericea endophyte positive and endophyte negative choices, and preferred Ipomoea carnea to Ipomoea asarifolia regardless of endophyte status. Nutritional composition, including non-structural carbohydrate concentrations, did not explain cattle preferences. This work suggests that for these toxic plant species, endophyte status plays no part in preferences of grazing livestock. Under Sub-Objective 5.2, ARS scientists determined the susceptibility or resistance to larkspur poisoning of cattle. Susceptible and resistant heifers were artificially inseminated with semen from similarly responding bulls. We are currently waiting for some of these calves to be born. Calves from this last year are being trained and their susceptibility will be determined.
1. Larkspur poisoning is sex-dependent in yearling Angus cattle. Female cattle respond differently to larkspur than males. ARS scientists in Logan, Utah, tested yearling Angus bulls, steers and heifers (a total of 123 cattle) with the same dose of larkspur. The severity of the poisoning depended on the sex of the cattle. Heifers had a 3.3-fold increased risk of susceptibility to larkspur poisoning compared to bulls. The 3.3-fold greater relative risk for larkspur poisoning emphasizes the importance of the careful management needed when grazing Angus heifers on larkspur-infested rangelands.
2. Larkspur poisoning in cattle is age-dependent. ARS scientists in Logan, Utah, dosed Angus steers with the same dose of larkspur as yearlings and again when they were two years of age. The results from this experiment indicated that yearling steers are more susceptible to larkspur poisoning than two-year-old steers. There were also age-dependent changes in the ability of the steers to clear the larkspur alkaloid from their body as they aged. These results suggest that older cattle are more tolerant of larkspur and thus better suited to graze in larkspur-infested rangelands.
3. Evaluation of noninvasive specimens to determine livestock ingestion of toxic plants. Poisoning of livestock by plants often goes undiagnosed because there is a lack of appropriate or available specimens for analysis, especially in dead animals. ARS scientists in Logan, Utah, detected Lupine alkaloids in the earwax, hair, oral fluid, and nasal mucus in cattle that were administered a single dose of Lupinus leucophyllus. In addition, alkaloids from lupine were detected in the earwax of cattle that grazed lupine-infested rangelands. Larkspur alkaloids were detected in the earwax, hair, oral fluid, and nasal mucus in cattle that were administered single doses of Delphinium barbeyi and Delphinium ramosum. 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. Special equipment is not required, and untrained personnel can easily collect the samples for analysis.
4. Larkspurs contain mixtures of toxic alkaloids that differentially intoxicate cattle. Larkspurs contain mixtures of toxic alkaloids and these mixtures can change based upon the geographic location and species of the plants. A chemical fingerprint/chemotype for larkspur plants from six geographic locations was determined by ARS scientists in Logan, Utah. A model was developed to predict chemotype toxicity based upon alkaloid concentrations and alkaloid subtypes. Each of the six plant chemotypes was evaluated in cattle. Results from this experiment showed that a chemotype of D. geyeri (plains larkspur) possessed the greatest toxic potential, as was predicted by the model.
5. Correlation of available selenate with uptake by western aster. Western aster with potentially lethal amounts of selenium grow on historic reclaimed phosphate mine sites in the western U.S. Understanding the correlation between soil and forage selenium concentrations is limited. An ARS scientist in Logan, Utah, used a hydroponic model to demonstrate the correlation between solution selenate concentrations and leaf selenium concentrations in western aster. This information is helpful to regulatory agencies and mining officials to better understand the potential risk that soils with high selenate concentrations may present if selenium accumulator species, such as western aster, grow on these soils.
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