Important Poisonous Plants of the Western United States Chemistry: Characterize, quantify & purify plant toxins, ELISA development Plant Biochemistry & Physiology: Genetic & environmental influences on toxins; chemical phenology; chemotaxonomy; toxin synthesis Vet Sci & Toxicology: Pathology (diagnosis/ prognosis), toxicokinetics, mechanism of action Core Solutions An interdisciplinary approach used by the Poisonous Plants Research Laboratory in Logan UT. The mission of the Poisonous Plant Research Laboratory is to identify poisonous plants and their toxins, determine how the plants poison animals, develop diagnostic and prognostic procedures, identify the conditions under which poisoning occurs, and develop management strategies and treatments for ranchers to reduce livestock losses. Reference for this lesson is available as a pdf. https://www.ars.usda.gov/is/np/poisonousplants/poisonousplants.pdf and can be downloaded as companion material in the rangeland teaching clearinghouse. Animal & Range Science: Effects of toxins on reproduction, animal physiology, behavior & nutrition; genetics; plant population ecology; consumption of toxic plants by grazing animals

Losses to Toxic Plants Death Impaired Gains Abortions Birth Defects Indirect Losses: Vet costs Change in management Increased risk Decreased land value Total losses to U.S. livestock industry exceed $300 million annually. 3-5 percent of all livestock that graze on western rangelands are adversely affected by toxic plants. USDA -ARS USDA -ARS This set of 25 slides will show and discuss some of the more economically important toxic plants according to the USDA-ARS Poisonous Plant Research Laboratory. It will take approximately 150 minutes to cover the material in this set of slides and another 35 minutes to administer and review the quiz in the noteguide. USDA -ARS USDA -ARS

The Dose Makes the Poison “All substances are poisons; there is none which is not a poison. The right dose differentiates a poison from a remedy.” Paracelsus (1493-1541) LD50 – Lethal dose, the amount of toxin needed to kill 50% of test population, usually expressed in mg/kg Active ingredient/toxin Alkaloid-accumulating plants Larkspur, locoweed, lupine Nitrate-accumulating plants Milkvetch, stressed annual crops such as oat hay, corn, sudangrass Selenium-accumulating plants Asters, princess plume, milkvetch Cyanide toxicity Chokecherry, arrow grass, service berry The importance of knowing the active ingredient or toxin helps in determining management strategies and possible remedies.

Larkspur (Delphinium spp.) Divided into three categories Tall - Found in moist mountain sites 6,000-10,000 feet elevation in the western U.S. grows 3-6 feet tall. (D. barbeyu, D. occidentale, D. glaucescens, D. glaucum, and D. ramosum) Low - Grows early in spring on foothill and mountain ranges 3,000-6,000 feet elevation 6-30 inches tall. With adequate moisture may persist for 6-8 weeks. (D. nuttallianum, D. andersonii, D. scaposum, and D. bicolor) Plains – Problem on high plains of Colorado and Wyoming, 2-3 feet tall. (D. geyeri) Responsible for $6-10 million in losses annually Marsh (1913) stated that larkspurs kill more cattle on western ranges than any other plant. Currently today larkspur is still the most toxic plant to cattle on western rangelands. However the plant that kills the most livestock in the U.S. is alfalfa.

Identifying larkspurs Upper sepals extend into a spur Petals bluish-purple Leaves alternate, simple, petiolate, blades palmately divided, divisions 3-9, divisions cleft, (petiole) Fruit pod-like follicle when dry looks like a Jester hat USDA -ARS It would be ideal to have some plant mounts to pass around the class to show the key identification characteristics of all the plants discussed in this set of slides. USDA -ARS USDA -ARS

Clinical signs of larkspur poisoning The relative toxicity and concentration of individual alkaloids varies among species of larkspur. The toxic alkaloids cause death by neuromuscular paralysis. Weakness and staggering gait; animal may fall suddenly Salivation Muscular twitching Difficulty breathing – rapid and shallow Nausea and vomiting Rapid irregular pulse Death occurs from respiratory paralysis and/or bloat Excitement intensifies all signs of poisoning The cholinergic drug “Neostigmine “(0.02mg/kg intermuscular) has been successfully used to reverse clinical larkspur intoxication. Drug therapy is not practical in most range situations, catching and constraining the animal will aggravate the symptoms and cause death. USDA -ARS

Factors that influence ingestion and toxicity to cattle Time of year and stage of growth Cattle eat less larkspur during drought Amount of larkspur present Current vegetation composition Some cattle breeds tend to be more tolerant than others Some species of larkspur are more toxic than others How many consecutive days larkspur is consumed The understanding of the toxic window has lead to cattle managers deferring grazing in high larkspur concentrated areas until after flowering. J.A. Pfister

Sheep resistance to larkspur Sheep must eat 4-5 times more larkspur to show symptoms of poisoning compared to cattle. Research has shown sheep have an affinity to bind methyllycaconitine (MLA) at neuromuscular junction. Thus reducing the effect of MLA on muscular paralysis. Methyllycaconitine is most common toxic alkaloid in larkspur (LD50 is about 4 mg/kg in mice) Symptoms of poisoning can be seen in sheep if they are herded or excited. Kay Benson

Management of larkspur Avoid toxic window Create larkspur free areas if possible Herbicides – 1oz Metsulfuron-methyl tank mixed with 1pint 2,4-D ester formulation sprayed in vegetative stage has resulted in 90% control. Dead plants are palatable and potentially toxic-no grazing for one year. Graze sheep before cattle Consider aversive conditioning Use rider to redistribute animals Do not excite animals it will exasperate the toxicity Low larkspur can be controlled with 2-4-D. Tall larkspur can be controlled with picloram. Both these herbicides will damage other broadleaf forbs and shrubs as well.

Lupine (Lupinus spp.) Five poisonous species (Lupinus sericeus), (L. caudatus), (L. leucophyllus), (L. argenteus), and (L. formosus) Species are not uniform in alkaloid composition Not all species contain teratogenic alkaloids Toxic species are toxic entire growing season, younger plants are more toxic than older plants. Lupine is a native legume that fixes nitrogen. It will form a seed pod and has a very characteristic palmate leaf. USDA -ARS USDA -ARS

Lupine induced crooked–calf syndrome Teratogenic alkaloids may cause death to sheep and cattle depending on the stage of growth and amount consumed. In cattle if consumed during day 40 -100 of gestation malformations such as cleft palate, torticollis and kyphosis may occur in the calf. Torticollis Kyphosis Cleft palate Lupine is very toxic to sheep and typically causes birth malformations in cattle. USDA -ARS USDA -ARS USDA -ARS

Lupine management Grazing occurs as a function of palatability and availability compared to other vegetation present. Cattle with higher Body Condition Scores (BCS) tend to consume less lupine than cows of lower BCS. Graze steers or bulls in pastures with teratogenic lupine species. Shift breeding dates to avoid toxic window for mother cows. No known treatment for lupine poisoning. USDA -ARS

Locoweed (Astragalus spp.) (Oxytropis spp.) Astragalus and Oxytropis species that contain the toxin swainsonine. Fungal endophyte isolated from toxic locoweeds that produce swainsonine. Rank order of toxicity, garbancillo (A.wootoni) > wooly loco (A. mollissimus), = spotted loco (A. lentiginosus) > white point loco (O. sericea) Locoweeds tend to grow cyclic, because many are short lived perennials or annuals depending on precipitation patterns. USDA -ARS

Locoweed production cycles Oxytropis, generally are long lived perennial plants. Green locoweed leaves are selected by cattle, horses, and sheep in grazing trials. Astragalus, generally are cyclical based on fall and spring precipitation. Many locoweeds begin growth before cool season grasses. Locoweeds remain palatable late in the fall after warm season grasses have gone dormant. Palatability is a function of other available forage. Healthy rangeland conditions with perennial bunchgrasses will reduce the consumption of locoweeds, therefore reducing the occurrence of poisoning. White point loco Spotted loco USDA -ARS USDA -ARS

Locoweed losses Spanish word “loco” means (crazy), which describes the behavior of poisoned animals. Abnormal behavior such as extreme nervousness, inability to eat and drink. Abortions and reduced libido Wasting type of condition, dull eyes and dry hair coat. There is no effective treatment for locoweed poisoning. USDA -ARS

Ponderosa pine (Pinus ponderosa) Abortions in cattle from pine needles Affects only cattle in mid to late gestation Weather forces cattle to take shelter under ponderosa pine trees Low BCS cows eat more needles than higher BCS cows Dead calves and retained placenta Prevent access to pine trees during last trimester of pregnancy Keep cows out of pastures with ponderosa pine trees during late gestation. USDA -ARS USDA -ARS

Broom snakeweed (Gutierrezia sarothrae) Threadleaf snakeweed (G Broom snakeweed (Gutierrezia sarothrae) Threadleaf snakeweed (G. microcephala) Toxins probably terpenes, similar to pine needle abortion More toxic on sandy soils than on limestone soils Abortions and retained placenta Another weather influence consumption of a plant that is normally not very palatable. USDA -ARS

False hellebore (Veratrum californicum) Sometimes called wild corn or cow cabbage Grows on moist open meadows and hillsides at 6,000-11,000 feet elevation Toxicity decreases as plant matures Causes monkey-faced lambs if ewe consumes it on 14th day of gestation Remember sheep are short day breeders, so false hellebore should not be present in fall breeding pastures. USDA -ARS USDA -ARS

Death camas (Zigadenus species) Contains toxic steroidal alkaloids Entire plant is toxic and dangerous at all times Begins growth early in the spring Causes salivation, nausea, vomiting, staggering, convulsions and death Sheep are most susceptible but cattle, horses and humans have been poisoned Can be confused with wild onion. Grows at high elevations and is usually early to green-up. Sheep carcasses USDA -ARS USDA -ARS

Yews (Taxus spp.) Shrubs used for landscaping Most poisoning occur from feeding livestock trimmings Most toxic of all poisonous plants Cardiovascular toxin Very small amount of plant material needed to be fatal Be careful with some of the ornamental shrubs grown in the west. Do not feed trimmings to livestock. Cattle fed clipping Japanese yew USDA -ARS

Halogeton (Halogeton glomeratus) Invasive annual plant, grows in disturbed area such as road sides and trails Thrives in saline soils Seed bank is viable up to 20 years Toxic substance is sodium oxalate Becomes more toxic as it matures Usually a problem on winter range allotments. 1200 dead sheep USDA-ARS

Nitrate accumulating plants Rapid growing annual crops/weeds (oat hay, corn, kochia, pigweed and nightshade) accumulate nitrates Drought conditions may cause nitrate accumulation Nitrates are converted to nitrite by rumen microbes Nitrite causes the production of methemoglobin Methemoglobin can not carry oxygen resulting in blue coloration of membranes around mouth and eyes If not fatal may cause abortion Test feed and do not feed if concentrations of KNO3 is greater than 1.5% on a dry weight basis Can diluted with low-nitrate forage Some aftermath feeds can be high in nitrates as well such as corn stalks and wheat straw. Be aware nitrate poisoning can be caused by high levels of nitrogen in water.

Selenium accumulating plants Plants containing more than 5 ppm selenium are potentially toxic Primary accumulator group includes milkvetchs (Astragalus spp), woody aster (Machaeranthera section Xylorrhiza) and princes plume (Stanleya pinnata) Secondary accumulator group includes saltbush (Atriplex spp), Indian paintbrush (Castilleja spp),and gumweed (Grindelia spp) Nonaccumulator group includes grasses such as western wheatgrass and small grains most problematic because they are readily consumed by livestock Sheep do not show the typical signs of poisoning, they are more susceptible to sudden death.

Symptoms of selenium toxicity Acute poisoning Abnormal posture Unsteady gate Diarrhea Increased pulse and respiration rate Death Chronic poisoning Dullness Rough hair coat Loss of long hair Hooves may become overgrown Lameness Use of soil maps may show pastures that may lend themselves to selenium accumulation in plants.

Cyanide toxicity Cyanogenic glycosides are converted to cyanogenic acid by rumen microbes resulting in poisoning Young plant tissue highest in HCN Frost and drought can increase HCN concentration Herbicides may increase HCN concentration Plants that are cyanide toxic Johnson grass (Sorghum halapense) Sudan grass (Sorghum vulgare) Chokecherry (Prunus virginiana) Service berry (Amelanchier alnifolia) Arrow grass (Triglochin spp.) Death is usually very rapid. Chokecherry leaves are the toxic part of the plant.