Project : USDA ARS

ARS Home » Pacific West Area » Logan, Utah » Poisonous Plant Research » Research » Research Project #436003

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

Location: Poisonous Plant Research

2022 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 Objective 1, ARS researchers at Logan, Utah, grazed sheep on death camas (Zigadenus paniculatus) infested rangelands to determine if a state of hunger will increase an animal’s preference to consume death camas. Sheep were grazed at two locations in Utah in 2019 and 2021 as well as one location in Idaho in 2022. Sheep were grazed when the plant was in the early vegetative stage of plant growth and again when the plant was in the flower stage, to determine if the phenological growth stage of death camas affects a sheep’s preference to consume the plant. Under Sub-objective 1.2, ARS researchers at Logan, Utah, evaluated several herbicides for control of plains larkspur (Delphinium geyeri) at a location in Wyoming and another in Colorado to determine if newly developed herbicides can control plains larkspur. Plots were sprayed with herbicides in Wyoming during the summer of 2021. Those plots were evaluated for control during the summer of 2022. Plots in Colorado were sprayed with herbicides during the summer of 2022. The herbicides were applied at two different times of plant growth. First application was during the early vegetative growth stage and the second application was when plants were in the flowering stage. The results suggest that several herbicides can provide good control of plains larkspur. Under Sub-objective 1.3, ARS researchers at Logan, Utah, conducted experiments in a greenhouse which demonstrated that an iron soil amendment (zero valent iron) will inhibit selenium uptake into selenium-accumulating forages grown in soils containing high amounts of selenium. This soil amendment was also found to increase forage mass of non-accumulator forages in the same soil. In support of Objective 2, ARS researchers at Logan, Utah, continued research to characterize the alkaloid profiles from several Delphinium species that had not been investigated previously. Methyllycaconitine, the larkspur toxin most commonly associated with poisoning of cattle, was detected in most species tested. Additionally, two Delphinium species were collected over the growing season in 2020, 2021 and are currently being collected over the growing season of 2022 at nine different locations to determine how alkaloid concentrations change over the growing season and between years and how they might vary at different locations. Under Sub-objective 2.2, ARS researchers at Logan, Utah, surveyed several Astragalus species for swainsonine and selenium and are in the initial stages of preparing a publication. Under Sub-objective 2.4, ARS researchers at Logan, Utah, have completed an analysis of the macro and micro-nutrients from treated plants and are in the initial stages of preparing a publication. In support of Sub-objective 2.7, ARS researchers at Logan, Utah, have identified herbarium collections representing the taxa of interest and initial collections have started. Chemical analysis has been initiated on select samples. In support of Objective 3, ARS researchers at Logan, Utah, collected earwax in the fall of 2021 from 69 pregnant cows that grazed pastures containing teratogenic lupine plants throughout the summer of 2021. Nine of the 69 cows gave birth to malformed calves (terata). The earwax samples were analyzed for teratogenic alkaloids. Concentrations of teratogenic alkaloids in earwax samples were found to not correlate with cows that gave birth to malformed calves and those that had normal births. Under Sub-objective 3.4, ARS researchers at Logan, Utah, determined that inhibition of serum mannosidase by swainsonine is variable and under these conditions, correlation with tissue or species susceptibility to locoweed-induced disease is not apparent. More work is needed to increase sensitivity and better defining the inhibitory constant (Ki), as the marked variation is both tissue and species reaction to mannosidase inhibition suggests there are differences in swainsonine mannosidase binding affinity. Additionally under Sub-objective 3.4, ARS researchers at Logan, Utah, concluded studies to evaluate the carcinogenic nature of six different dehydropyrrolizidine alkaloids using a P53 knockout mouse model. Dosing of the last two experimental groups has begun and those animals will finish later this year. The histological analyses of previously treated mice are mostly completed. In support of Objective 4, ARS researchers at Logan, Utah, conducted an experiment to determine if cattle would decrease their overall feed intake after being poisoned by larkspur (Delphinium spp.). Samples are in the process of being analyzed for nutrition content and data is being prepared for statistical analysis. Under Sub-objective 4.3, ARS researchers at Logan, Utah, demonstrated that feeding high selenium containing forage to sheep causes early disruption of spermatogenesis resulting in decreased sperm motility and increased morphological abnormalities without causing other signs of toxicity. Similar trials in cattle had very little negative impact on sperm quality, however clinical signs of chronic selenium poisoning were observed. Testicular lesions were examined microscopically and have been classified as an early disruption of spermatogenesis. A grading method was also developed, and the second review and grading evaluation of these studies was completed. This histology work will be correlated with chemical analysis and those publications are in preparation. In support of Objective 5, ARS researchers at Logan, Utah, demonstrated that larkspur toxicity is both age and sex dependent in cattle. After evaluating the past 15 years of research, ARS researchers at Logan, Utah, have rejected their hypothesis that larkspur susceptibility in Angus cattle is a heritable trait. Efforts have been redirected towards using a mineral mix to reduce the impact of larkspur on cattle.

Accomplishments
1. Mineral-salt supplementation protects against larkspur poisoning in cattle. Larkspurs (Delphinium spp.) are toxic to cattle and cause the livestock industry millions of dollars in losses every year. Finding inexpensive solutions to help reduce cattle losses would be beneficial to the livestock producer and the food supply chain. In pen feeding trials, ARS researchers in Logan, Utah, found animals supplemented with a mineral-salt were more resistant to larkspur toxicosis than non-supplemented animals. Animals supplemented with the mineral during a rangeland grazing study were found to consume less larkspur. These results suggest that a good mineral supplementation program could provide a protective effect for animals grazing in larkspur-infested rangelands.

2. A new method for detection and quantification of larkspur toxins. Larkspurs contain toxic norditerpene alkaloids, which have most recently been analyzed by a Fourier infrared spectroscopic method. ARS researchers in Logan, Utah, developed an alternative method to measure toxic and total alkaloids was developed using flow-injection mass spectrometry and validated to replace the older method. The new method is more rapid and requires less sample preparation than the previous method. The new method will provide better and less expensive support for research projects and diagnostic cases.

3. Diazepam as a treatment for water hemlock poisoning. Water hemlock (Cicuta maculata) is one of the most toxic plants in north America to livestock and humans. ARS researchers in Logan, Utah, evaluatded therapeutic options to determine what drug is best for treating livestock poisoned by water hemlock. The actions of several benzodiazepines and barbiturates on water hemlock poisoning in goats were compared. The benzodiazepine, diazepam, was effective at managing the clinical signs of water hemlock poisoning. The results of this research suggest that diazepam could be an effective treatment for water hemlock poisoning in livestock species and humans.

4. Swainsonine containing Ipomoea species and their association with fungal symbionts. Understanding host symbiont relationships is critical to our basic understanding of the synthesis of some plant toxins such as swainsonine. ARS researchers in Logan, Utah, in collaboration with New Mexico State University researchers investigated the association of the fungal symbiont in its host using different types of microscopy. This research provides valuable basic information to other scientific researchers about the nature of the symbiosis between a host (plant) and a symbiont (fungus). Understanding these associations may provide important understanding of mechanisms to disrupt the association, which would render the plant less toxic.

5. Swainsonine containing Ipomoea species. Understanding the chemical composition of plant taxa is required to better predict risk of poisoning and make recommendations to reduce livestock losses. ARS researchers in Logan, Utah, in collaboration with other researchers surveyed over 200 Ipomoea species for the toxin swainsonine. Swainsonine was identified in 32 species, most of which were previously not known to contain swainsonine. The information learned from this research may be helpful to extension agents and range scientists at various government agencies, as well as livestock producers, and other investigators studying toxic plants and natural products. This research has significant impact as it has saved the lab several hundred-man hours and tens of thousands of dollars that would have been used making field collections.

6. Salt desert shrub plant communities are influenced by precipitation. Drought conditions are altering vegetation dynamics on salt desert shrub plant communities. There is a lack of long-term data sets following vegetation dynamics on these plant communities. ARS researchers in Logan, Utah, examined thirty years of plant foliar cover and found that native shrub cover and warm-season grass cover increased when cool-season precipitation was available. Climatic conditions were a dominant influence on the vegetation in the salt desert shrub plant community. This data will provide valuable information for future science-based policy decisions with regards to the management of salt desert shrub plant communities.

7. Broom snakeweed does not directly cause late term abortions in cattle. Broom snakeweed (Gutierrezia sarothrae) and threadleaf snakeweed (G. microcephala) are found on many rangelands in western North America, and there are field reports that pregnant cows that graze snakeweeds may abort calves. Snakeweeds are generally unpalatable; however, animals will graze them when other forage is not available. ARS researchers in Logan, Utah, fed late-term pregnant cattle with plant material or with solvent extracted compounds from snakeweeds to test the extracts for abortifacient activity in late-term pregnant cattle. Neither the plant material, nor the dosed extracts, appear to be able to directly cause abortions in cattle. This research suggests that broom snakeweed plants are unlikely to be directly responsible for cattle abortions observed in cattle grazing snakeweed infested rangelands. It is more likely that cattle may be affected by rumen toxicity and/or might suffer from poor nutritional factors given the lack of quality forage available on rangelands with high snakeweed infestation.

8. Identification of two death camas chemotypes in a plant population. Foothill death camas (Zigadenus paniculatus) is a bulbous perennial forb that is toxic to both sheep and cattle. A population of death camas with two different chemical profiles (chemotypes) was found growing within the same location. ARS researchers in Logan, Utah, conducted experiments to determine if there was a difference in toxicity between the two chemotypes in multiple species of animals. Based on the results of the study, caution should be taken when livestock are grazing death camas, as both chemotypes appear to pose a similar risk of poisoning to grazing livestock.

U.S. DEPARTMENT OF AGRICULTURE

Poisonous Plant Research: Logan, UT