Project : USDA ARS

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Research Project: Developing Mitigation Strategies for Poisonous Plants in Livestock Production Systems

2024 Annual Report

Objectives
Objective 1: Develop science-based guidelines to reduce livestock losses on rangelands, including evaluating differences in toxin accumulation in poisonous plants. Sub-objective 1.A: Evaluate herbicides to determine efficacy in controlling Geyer larkspur (Delphinium geyeri) and determine if the toxicity of Geyer larkspur changes due to herbicide treatment. Sub-objective 1.B: Determine the effect of forage selenium concentrations on relative palatability, and subsequent productivity in livestock. Sub-objective 1.C: Characterize changes in norditerpene alkaloids in Delphinium species among geographical locations, plant parts, and over the growing season. Sub-objective 1.D: Screen herbarium specimens representing species of different genera (Delphinium, Zigadenus, Astragalus, Oxytropis, and Salvia) for suspected toxins. Objective 2: Enhance methods for analyzing plant and animal tissues for plant toxins, measuring toxicokinetics, assessing carcinogenic and genotoxic potential, as well as identifying plant toxin metabolites and biomarkers of toxicoses. Sub-objective 2.A: Evaluate the utility of earwax and hair as noninvasive specimens for diagnosis of livestock exposure to additional poisonous plants (death camas, locoweed, and lupine). Sub-objective 2.B: Characterize the carcinogenic potential of purified dehydro-pyrrolizidine alkaloids (DHPA’s) (lasiocarpine, seneciphylline, senecionine, heliotrine and their n-oxides) and compare these with known DHPA carcinogens. Sub-objective 2.C: Determine primary serum and rumen biomarkers for livestock poisoned by death camas. Sub-objective 2.D: Evaluate DNA metabarcoding technologies as a diagnostic method for poisoned animals and contaminated feeds. Objective 3: Develop improved diagnostic and prognostic procedures to reduce negative impacts of poisonous plants on livestock including early identification of poisoned animals, predicting poisoning outcomes, as well as best management and treatment options. Sub-objective 3.A: Compare the pathological changes in livestock poisoned by Ipomoea carnea with and without swainsonine. Sub-objective 3.B: Determine the effects of chronic exposure to excessive amounts of selenocompounds commonly found in supplements and forages, on spermatogenesis and sperm quality in sheep. Sub-objective 3.C: Develop drug treatments for livestock that are poisoned by poison hemlock. Sub-objective 3.D: Determine the potential toxicity and teratogenicity of hemp to livestock. Objective 4: Develop guidelines to aid producers and land managers in making evidence-based herd management decisions to improve livestock performance on rangelands infested with poisonous plants. Sub-objective 4.A: Determine if mineral supplementation can reduce plant-induced poisonings of livestock. Sub-objective 4.B: Characterize conditions that cause sheep to become poisoned when grazing on death camas-infested rangelands. Sub-objective 4.C: Compare the susceptibility of cattle that are native to larkspur-infested ranges to cattle that are naïve to larkspur-infested ranges. Sub-objective 4.D: Comparison of the susceptibility of taurine and indicine cattle to lupine toxicosis.

Approach
There are hundreds of genera of toxic plants, representing thousands of species. Plant poisonings occur worldwide including 333 million hectares infested with poisonous plants in China and 60 million hectares in Brazil. The livestock industry in the western United States loses over $500 million annually from death losses and abortions due to poisonous plants. Actual losses due to poisonous plants are much greater due to wasted forage, reduced animal performance, and increased management costs. 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 the scientific community. 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. Our mission is to develop research-based solutions to reduce livestock losses from toxic plants. There are four 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-containing plants utilizing the various scientific disciplines of the staff. The products of this research will help to 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
This report documents FY 2024 progress for project 2080-21500-001-000D, "Developing Mitigation Strategies for Poisonous Plants in Livestock Production Systems", which started December 2023 and continues research from project 2080-32630-014-000D, "Understanding and Mitigating the Adverse Effects of Poisonous Plants on Livestock Production Systems". In support of Objective 1, further work was conducted to evaluate the risk of animals being poisoned by different species of larkspur. Larkspurs (Delphinium spp) are one of the most problematic poisonous plants on the rangelands of the western United States, causing millions of dollars in losses to livestock producers annually. There are a number of different species of larkspur found throughout the western United States. The toxic components of larkspurs are the norditerpenoid alkaloids, of which there are more than 18, with greater than 30-fold differences in their toxicity. ARS scientists in Logan, Utah, have studied the toxic effects of larkspurs for many years, utilizing different methods of collecting, processing, analyzing the alkaloid content, and determining toxicity of the plants. These differences can contribute significantly to variations in responses. Consequently, the objective of this work was to collect, process, chemically analyze, and test the toxicity of 20 different species of larkspurs all using the same methods by the same researchers. This data will provide a more defined risk assessment for the various species of larkspurs found in the western United States. This data will be beneficial for scientists, livestock producers, extension agents, and veterinarians to evaluate the risk of grazing livestock in the various larkspur infested rangelands of the western United States. For Objective 2, further work was conducted to evaluate the acute toxicity of death camas. Death Camas (Zigadenus spp.) is a common poisonous plant found throughout North America in diverse habitats. The toxic alkaloids in foothill death camas are zygadenine, esters of zygadenine, including zygacine, angeloylzygadenine, and veratroylzygadenine. Zygacine is often the most abundant alkaloid in death camas and has been believed to be the primary toxic component. However, not all alkaloids in death camas have been identified, nor have their toxicities been determined. Even though zygacine is the major alkaloid in Z. paniculatus, previous research has shown that additional alkaloids in death camas contribute to its toxicity in a mouse model. Consequently, the objective of this study was to determine if there is a difference in the acute toxicity of zygacine and zygadenine to both mice and sheep and to evaluate the toxicity of angeloylzygadenine and veratroylzygadenine. Due to the fact that zygacine is rapidly metabolized to zygadenine via a first pass effect when administered orally, the acute toxicity of zygacine and zygadenine were compared in mice and sheep dosed intravenously in order to bypass the first pass effect. Overall, these data indicate that zygacine is more toxic than zygadenine; however, zygacine is metabolized very quickly, thus, if an animal has been exposed to zygacine and can live long enough to cleave the ester bond, the animal will survive. Additionally, the data suggest that the rank order of toxicity of the death camas alkaloids are veratroylzygadenine > angeloylzygadenine > zygacine > zygadenine. Under Objective 3, plant material was obtained to develop a drug treatment for livestock poisoned by poison hemlock and the plant material needed to test the hypothesis that phytocannabinoids present in hemp and hemp byproducts have the potential to cause craniofacial defects in livestock. The poison hemlock plant material was analyzed for piperidine alkaloid concentrations, and the hemp plant material was analyzed for cannabinoid concentrations. Supporting Objective 4, ARS researchers conducted further work to evaluate the acute toxicity of death camas. Livestock losses to death camas have been reported in numerous species including cattle and sheep, with the largest losses generally occurring in sheep. Clinical signs of poisoning are similar for all animal species studied. In a recent study to develop methods to aide in the diagnosis of animals poisoned by death camas, goats were dosed with death camas as a small ruminant model for method development purposes. In that experiment, the goats demonstrated less clinical signs of poisoning than had been noted in sheep given a similar dose in a previous experiment. Thus, ARS researchers hypothesized that goats may be more resistant to the toxic effects of death camas than sheep. The objective of this research was to compare the susceptibility of goats and sheep to the acute toxic effects of death camas. The data presented in a published manuscript demonstrates that goats are more susceptible to the acute toxic effects of death camas. Consequently, any rancher that may consider grazing goats in death camas infested pastures should use as much caution, if not more, than they would with sheep. Additionally, the data presented in the study, suggests that goats can be used as a small ruminant model to study the toxic effects of death camas. In additional support of Objective 4, the acute actions of lupine alkaloids were compared between temperate and tropical cattle. ARS scientists in Logan, Utah, used time to exercise fatigue at 24 hours after oral dosing to measure differences in the responses to lupine between the two landraces of cattle. Twenty-four hours following dosing, the steers were exercised, and upon experiencing exercise fatigue, the steers were allowed to stop, and the duration of their walk was recorded. Temperate cattle were somewhat resistant to the effects of lupine alkaloids; however, all of the tropical cattle died. The lethal nature of this dose of L. leucophyllus in tropical cattle has not been previously reported. The results from this study demonstrate that the acute, adverse effects of lupine alkaloids are more severe in tropical cattle. If cattle ranchers opt to manage the effects of increasing summer temperatures by grazing tropical cattle, additional care must be taken on rangelands with toxic lupine and larkspur populations to prevent significant losses to their cattle from these poisonous plants.

Accomplishments
1. Mitigation of lupine-induced crooked calf syndrome through intermittent grazing of cattle. Lupines, a diverse group of plants known for their adaptability to various environments, pose a significant risk to livestock, particularly pregnant cattle, and when ingested, certain species of lupines can cause a condition known as "crooked calf syndrome," characterized by skeletal malformations in newborn calves. ARS scientists in Logan, Utah, determined whether an intermittent cattle grazing schedule could mitigate the incidence and severity of lupine-induced malformations in calves. Pregnant cattle subjected to the intermittent grazing regimen exhibited a significant decrease in the incidence of severe skeletal malformations in their offspring. This temporary intermittent grazing was crucial in preventing the development of severe malformations and represents a significant step forward in the sustainable management of rangelands and the health of grazing livestock.

2. Published case report of Salvia reflexa-contaminated hay poisoning in cattle. Salvia reflexa, commonly known as lanceleaf sage, is an annual herb that has been implicated in severe, often fatal, liver toxicity in cattle. ARS scientists in Logan, Utah, were consulted to investigate two notable cases of cattle poisonings attributed to Salvia reflexa. Case 1 (December 2001, Montana): Out of a herd of 105 cows, 30 succumbed to poisoning. Case 2 (2023, Wyoming): This case was even more severe, with 111 cows out of 155 dying. Blood samples from Case 1 and liver samples from both cases showed pathological and biochemical changes consistent with known cases of Salvia reflexa poisoning, including elevated liver enzymes and necrosis, indicative of severe liver damage. Liver toxins associated with Salvia reflexa were detected in hay samples from both incidents and in the rumen contents of animals from Case 2, confirming ingestion of the toxic plant. Given that toxic Salvia reflexa specimens were found in 12 states, there is a need for widespread monitoring and control measures to manage this plant’s distribution and prevent its incorporation into cattle feed.

3. Death as a result of poisoning tropical but not temperate cattle after oral dosing with velvet lupine. With the progression of climate change and increasing summer temperatures, livestock management practices are evolving with tropical cattle grazing in regions traditionally occupied by temperate cattle. This change introduces tropical cattle to new environmental hazards and risks, including toxic plants they may not be accustomed to, such as velvet lupine. To address this risk, ARS scientists in Logan, Utah, conducted a comparative study on the toxicity of velvet lupine (Lupinus leucophyllus) in both temperate and tropical cattle. Tropical cattle exhibited a higher mortality rate upon ingestion of velvet lupine compared to temperate cattle, indicating a potentially lower tolerance or unfamiliarity with the plant's toxic compounds. The higher susceptibility of tropical cattle to velvet lupine poisoning highlights the need for increased care and proactive management when these cattle are grazed in new environments, and by implementing vigilant monitoring, and adaptive grazing strategies, producers can better protect their herds from the toxic threats posed by velvet lupine and ensure sustainable livestock practices in a changing climate.

4. Ruminant metabolism of zygacine, the major toxic alkaloid in foothill death camas (Zigadenus paniculatus). Death camas species (Zigadenus spp.) are common and highly toxic plants that poison cattle and sheep throughout North America, and the primary toxic constituents of death camas are zygacine and zygadenine. ARS researchers in Logan, Utah, investigated the metabolic fate of zygacine in livestock. They hypothesized that enzymes such as esterases present in the rumen, liver, and blood would metabolize zygacine into zygadenine. This work documented that zygacine was metabolized to zygadenine in the rumen, liver, and blood of both sheep and cattle, and the rapid metabolism of zygacine to zygadenine suggests that diagnosticians should focus on detecting zygadenine, rather than zygacine, in the rumen and sera of livestock suspected of being poisoned by death camas. By demonstrating that zygacine is metabolized to zygadenine in the rumen, liver, and blood, this research provides critical insights that can refine diagnostic procedures and improve the management of death camas poisoning and proactive grazing management to safeguard the health and well-being of livestock in regions where death camas is prevalent.

5. Consequences of pollen defense compounds for pollinators and antagonists in a pollen-rewarding plants. Plants have evolved a defense mechanisms to protect themselves from herbivores, pathogens, and other threats, and one intriguing aspect of plant defense is the presence of toxic compounds in pollen. ARS scientists in Logan, Utah, in collaboration with researchers from the University of Ottawa, Ontario, Canada, investigated this phenomenon by testing three main hypotheses. First, the spillover hypothesis postulating that the compounds are present in pollen due to spillover from adjacent plant tissues; second, the pollen thief hypothesis which postulates that the compounds protect pollen from being stolen; and third, the antimicrobial hypothesis postulating that the compounds act as antimicrobial agents. Results from the study indicate that the presence of alkaloids in pollen does not deter pollen thieves, and that pollen alkaloids are negatively associated with bacterial abundance, providing strong support for their antimicrobial role. Understanding the roles of these compounds can improve our knowledge of plant-pollinator interactions, plant-pathogen dynamics, and overall plant fitness.

6. Selenium (Se) supplementation. Supranutritional selenium supplementation during the second and third trimesters of gestation increased immune response in beef cattle. ARS researchers in Logan, Utah, collaborated with researchers at Oregon State University to show that selenium supplementation increased serum neutralization titers for some viral antigens and enhanced complement-mediated bacterial killing in cows at parturition. These results suggest that Se supplementation may help against infectious diseases in cows around the time of calving to help reduce losses for ranchers.

7. Analysis of the mycotoxin levels and expression pattern of SWN genes at different time points in the fungus Slafractonia leguminicola. Slafractonia leguminicola is a fungal pathogen known for producing two mycotoxins that have significant effects on animals: slaframine, which induces a condition known as slobbers, and swainsonine, responsible for locoism. ARS scientists in Logan, Utah, and collaborators from New Mexico State University examined the production of swainsonine in S. leguminicola associated with a set of genes collectively referred to as the "SWN" gene cluster. This cluster includes: swnK, a multifunctional gene encoding an NRPS-PKS hybrid enzyme essential for swainsonine biosynthesis, swnH1 and swnH2, genes which encode a nonheme iron dioxygenase involved in the oxidative modifications of intermediates, swnN and swnR which encode reductases that contribute to the reduction steps in the biosynthetic pathway, and swnT, a transmembrane transporter responsible for the export of swainsonine. The study revealed several important insights into the biosynthesis and expression of the toxins, the timing of gene expression in both cultured fungus and inoculated leaves showed similar patterns. This consistency suggests that the proposed biosynthetic pathway is active under both conditions. The comprehensive analysis of gene expression and mycotoxin production in Slafractonia leguminicola underscores the complexity of fungal biosynthetic pathways, and this research enhances our understanding of toxin biosynthesis but also opens avenues for developing effective management and biocontrol strategies.

8. Embryotoxic effects of Veratrum alkaloids on bovine embryos. ARS scientists in Logan, Utah, examined how selected teratogens derived from Veratrum californicum influenced oocyte maturation and pre-implantation embryo development with in vitro fertilization (IVF) techniques, which provided a controlled environment to observe the cellular and developmental impacts of these natural toxins. Results from this study demonstrated that exposure of oocytes to cyclopamine and its synthetic analog cyclopamine-4-en-3-one during maturation inhibited cleavage rates and subsequent pre-implantation embryo development in vitro. This research indicates that ingestion of natural toxins such as these steroidal alkaloids can adversely affect oocyte maturation and subsequent pre-implantation embryo development.

U.S. DEPARTMENT OF AGRICULTURE

Poisonous Plant Research: Logan, UT