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

2021 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 scientists in Logan, Utah, established study plots at two locations and sprayed them with herbicides to determine if herbicides can aid in the establishment of newly seeded grass species in revegetated rangelands infested with poisonous pants. The first- and second-year evaluations have occurred. Study plots were also established at two locations and sprayed with herbicides to determine their efficacy in controlling death camas, and to determine if the toxicity of death camas changes due to herbicide treatment. Initial evaluations indicated that the herbicides 2,4-D, Crossbow, and Plateau were effective in controlling death camas, and there was not a difference between the early vegetative and flowering application time. In support of Objective 2, ARS scientists in Logan, Utah, continued research to determine 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. ARS scientists in Logan, Utah, surveyed several Astragalus species for swainsonine and selenium. Under Sub-objective 2.4 ARS scientists in Logan, Utah, have completed the macro and micro-nutrient analyses of the plants. Under Sub-objective 2.7, herbarium collections representing the taxa of interest have been identified and initial collections have been started. In support of Sub-objective 3.2, ARS scientists in Logan, Utah, conducted a series of studies to identify the major diterpene acids in broom snakeweed and their metabolites in serum. A manuscript describing the chemotypes in two snakeweed species was published. Large sample collections of the two most prominent chemotypes were collected and extracts were prepared for dosing in cattle. In vivo testing of both chemotypes in late-term pregnant cattle was completed. One of the chemotypes was found to be extremely toxic to the bovine rumen. Neither chemotype was found to induce abortions in the cattle. A manuscript summarizing the results is in preparation. Under Sub-objective 3.3, studies demonstrated that the in vitro inhibition of serum mannosidase by swainsonine in different animal species correlates with in vivo swainsonine toxicosis. Serum mannosidase activity and sensitivity to swainsonine has been characterized in horses, cows, goats and sheep. Studies to further characterize the inhibition of serum mannosidase by swainsonine are being conducted. Under Sub-objective 3.4, ARS scientists in Logan, Utah, further evaluated the carcinogenicity of specific pyrrolizidine alkaloids, including studying the carcinogenicity of purified individual toxins in a P53 knockout mouse model. In support of Objective 4, studies were conducted to characterize the effect of low-dose selenium intake in cattle and sheep. Mineral, biochemical, and histological analyses of the samples are underway. Additionally, ARS scientists in Logan, Utah, measured the therapeutic actions of several drugs for the control of water hemlock poisoning in a goat model. This research identified diazepam as a good drug treatment for goats acutely poisoned by water hemlock. This research suggests that diazepam can be used as an effective treatment for water hemlock poisoning in livestock species, and potentially humans. In support of Objective 5, ARS scientists in Logan, Utah, continue to determine if there is a genetic contribution to the susceptibility of cattle to larkspur poisoning. The ability of cattle to pass along genes to their offspring that would result in either susceptibility, or resistance, to larkspur poisoning is being further evaluated. Additionally, grazing studies were conducted with cattle previously characterized as susceptible or resistant to larkspur poisoning in a pen setting, to determine if there is a difference in their susceptibility in a grazing setting as well. Also, a grazing study was conducted to determine if good, or poor, mineral supplementation can affect susceptibility of cattle to larkspur poisoning.

Accomplishments
1. Acute liver toxicity in cattle by Salvia reflexa. The weedy plant Salvia reflexa was identified by ARS scientists in Logan, Utah, as the cause of poisoning in cattle by weed-contaminated alfalfa hay that had resulted in the death of 165 cattle from a herd of 500. Four toxic compounds were identified, and a direct link was established to implicate Salvia reflexa as the toxic weed in the contaminated hay. Salvia toxicity was confirmed in mice, goats, and cattle. The identification of the cause of poisoning allowed the cattle owners to recover the losses which “saved the ranch”. This is the first report of Salvia causing liver injury, and this information will be useful to veterinary practitioners and diagnostic laboratories in solving future cases where Salvia poisoning may be involved.

2. Herbarium specimens as a tool to investigate phytochemical composition. Understanding the chemical composition of plant taxa is required to better predict risk and make recommendations to reduce livestock losses. ARS researchers in Logan, Utah, summarized how herbarium specimens can be used as a tool to facilitate poisonous plant research. Herbarium specimens have been used to characterize the chemical composition of hundreds of species representing several groups (genera) of plants. The information learned from these phytochemical screens has been helpful to extension agents and range scientists at the various government agencies, as well as livestock producers, and other investigators studying toxic plants and natural products. This research has significant impact as it can save several hundred-man hours and tens of thousands of dollars that would be required to make field collections of a similar extent.

3. Soil amendments reduce the uptake of selenium by forages growing on seleniferous soils. ARS scientists in Logan, Utah, treated high selenium-containing soils from reclaimed mine sites with various amendments in an attempt to reduce the uptake of selenium by forages that grow on these sites, as forages grown on these soils can be toxic to livestock. The addition of iron as an amendment to high selenium soil resulted in 60 to 90% decrease in selenium concentrations in several forages, while simultaneously increasing the biomass of desired forages. The information obtained from this study indicates that iron treatment of soils with high selenium content can be used to decrease selenium concentrations in forages growing on these soils, which would decrease the risk to livestock, and wildlife, grazing on these ranges.

U.S. DEPARTMENT OF AGRICULTURE

Poisonous Plant Research: Logan, UT