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. Poisonous plants are estimated to affect 3-5% of cattle, sheep, goats, and horses in the western US. (Panter et al., 2011). Direct losses are due to decreased weight, reduced reproduction, failure to thrive, and sometimes death. Indirect costs include medical treatment, increased feed reequirements, altered grazing plans, increased fencing, and decreased forage availability (Panter et al., 2011). 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. Some of these plants produce toxins directly such as larkspur and lupine, while for others, such as locoweeds, the plants contain fungal endophytes that produce the toxic agents. Fungal endophytes of grasses (such as fescue) produce alkaloids that are toxic to grazing animals. Other poisonous plants are toxic due to the accumulation of nitrates or selenium from the soils in which the plants grow. Poisonous plants continue to cause large losses to the livestock industry through death, reduced production efficiency, reproductive dysfunction, and compromised harvesting of rangeland and pasture forages. New Mexico State University researchers concluded that calf and lamb crops in the western United States are reduced 7% overall from toxic plants, including birth defects, negatively impacting ranchers and rural economies (Holechek, 2002).  Other economic losses are substantial, but difficult to quantify, as significant amounts of nutritious forage are underutilized, and management costs are increased due to the threat of toxic plant-related livestock losses.  These direct and indirect losses from poisonous plants adversely affect the economic viability of individual ranches and nearby rural communities that rely on the livestock industry as a substantial portion of their economic base. Current management grazing strategies could be further refined to reduce livestock losses due to poisoning and to enhance animal welfare.  This in turn ensures proper, safe, and efficient use of available rangeland forage and feeds to provide the production of toxin-free animal products. This project will focus on poisonous plants in the western US that induce toxicoses in cattle, horses, sheep, and goats.

Larkspur and lupine are plants that directly produce toxic agents that are important in the western US. Larkspur (Delphinium spp.) poisons cattle, and sometimes horses, throughout western North America due to the toxic alkaloids that they produce (Green et al. 2009). Symptoms include muscle weakness, paralysis, and ultimately death. Grazing recommendations have been developed based upon the relative palatibility and toxicity of the plant resulting in a signficant reduction of losses (Pfister et al. 2002). Several toxic species of larkspur have been identified, as have the alkaloids they produce (Panter et al, 2002). However, not all populations are toxic or have the same alkaloid profile, and toxicity varies with time of the year. This information has also been used to help ranchers limit their losses.

Lupine (Lupinus spp.) are toxic to all livestock species with sheep being affected most often. Lupines are found in diverse habitats such as mountains and foothills in both wooded and open areas. While most species are toxic, only some contain contain the alkaloids that cause the tetragenic effects, including cleft palates and leg and muscule deformities (Panter et al., 2011). Consumption of lupines causes problems to the offspring of pregnant cattle because of quinolizidine alkaloids in the plant that harm the fetus (Pfister et al, 2016). Factors that influence symptom severity include stage of plant maturity and timing and amount of lupine consumed, as well as stage of pregnancy of the animal.

Locoweeds are Astragalus and Oxytropis spp. that are poisonous due to the fungal-produced indolizidine alkaloid swainsonine. Other species of Astragalus may accumulate selenium or nitro compounds (Fox et al., 1998). Locoweeds are the most widespread group of poisonous plants in the western United States (Graham et al., 2009) and also cause significant problems to sheep in China and Inner Mongolia. Consumption of the swainsonine-containing plants induces locoism in grazing animals such as cattle, sheep, and horses. Locoism symptoms include reproductive problems, cellular vacuolization, neurological damage, and lack of coordination (James et al., 1992). In New Mexico in 1985, over 10% of the cow/calf and 40% of the cow stocker operations reported losses of over $20 million from locoism (Torell et al., 2000). The fungal endophytes (Alternaria section Undifilum sp.) of the locoweeds that produce swainsonine are seed transmitted and do not harm their plant host (Pryor et al., 2009; Oldrup et al., 2010).

Several other plants are toxic due to the presence of plant-associated fungi that produce swainsonine and other toxins. The fungus, Slafractonia leguminicola, produces both swainsonine, causing locoism, and slaframine, inducing slobbers, in cattle and horses. The fungus also causes a plant disease, black patch, which is found in the southeastern US. In Australia, Alternaria sp. that inhabit Swainsona sp. produce swainsonine, inducing pea struck disease in sheep.

Perennial rygrass and tall fescue can contain fungal endophytes that produce alkaloids toxic to grazing mammals. These are problems in the southeastern US, Australia, and New Zealand. The fungi, Neotyphodium coenophialum, produces loline alkaloids, ergovaline, and other toxins that cause high respiration rates, intolerance to heat, poor animal gains, reduced milk production, depressed feed intake, and low conception rates in cattle, and tetragenic effects to horses. The fungal endophyte also has shown benefits to its grass hosts including herbivore defense (Clay 1990), increased heat and drought tolerance (Bacon and White, 2000), and improved plant vigor and resistance to some pathogens (Molyneux et al., 2007).

Effective management of poisonous plants has been difficult to implement and costly despite knowledge of which plants are toxic. Recommendations include restricting access to pastures for grazing, supplementing cattle feed so that they don’t graze on the poisonous plants, spraying herbicides, making sure plants have adequate salt and water, and reducing stress on the animals (Graham et al., 2009; Panter et al., 2011). Behavior modification of cattle and horses has also been attempted as a management option for plants such as locoweeds. Sustainable management programs that can be implemented in multiple states or regions are needed for these difficult problems.

Much more research on poisonous plants is necessary to adequately develop management programs. Rapid identification of plants, understanding the conditions under which the plant is most dangerous to animals, better knowledge of which toxins are present, and the mechanisms of toxicoses would greatly improve management. Understanding locoweed-fungal endophyte interactions and the tall fescue-fungal endophyte interactions can significantly impact plant/microbe interactions, secondary metabolite production and the continuum between mutualistic and commensalistic interactions.

      We propose establishment of a multi-state project to study poisonous plants, their impact, ecology, and management. Poisonous plants cause problems over a large geographic area and the researchers that are experts in the fields that address the problems are spread over many disciplines, many states, and over different groups, ie. state, county, universities, and government agencies. A multistate project will improve communication and research efficiency which are needed to determine the impacts on the rangeland grazing communities and for develoment of management solutions. This group will meet annually to discuss, assess, and prioritize research topics such as as toxicology, diagnostics, toxin detection, range management, as well as plant and fungal ecology and physiology. The group will develop an action plan to determine who will accomplish which aspects of the research, including identifying research of highest impact for management, and who will work together to seek funding for the highest priority research. The group will coordinate research to provide preliminary information needed to secure grant funding. The group will also bring together research resources including plant samples collected from various locations, and provide periodic written documents reviewing the status of plants, and management both for dissemination among collaborating institutions and throughout range communities. Incorporating research from multiple states will contribute to management solutions for local, state-wide, and national poisonous plant problems as well as decreasing duplication of research and increasing dissemination of results. This work can benefit society by helping to more completely understand poisonous plants which in turn may ultimately protect the food supply by aiding ranchers whose livestock is impacted.