Poisonous plants are among the important causes of economic loss to the production animal industry and should be considered when evaluating illness and decreased productivity. Poisonous plants can affect animals in many ways, including the following:
death
chronic illness and debilitation
decreased weight gain
abortion
birth defects
increased parturition interval
photosensitization
Other considerations include loss of forage, additional fencing, increased labor and management costs, and, frequently, interference with proper harvesting of forage.
Most poisonous range plants fall into two general categories: those that are indigenous to a range and increase with heavy grazing and those that invade after overgrazing or disturbance of the land. Among those not in these categories are certain locoweeds and larkspurs, both of which form part of the normal range plant community. Poisonous plants can be found in most plant communities and should be considered in most grazing situations.
Poisoning of production animals by plants often can be traced to problems of management or range condition, rather than simply to the presence of poisonous plants. Usually, animals are poisoned because hunger or other conditions cause them to graze abnormally. Overgrazing, trucking, trailing, corralling, or introducing animals onto a new range tends to induce hunger or change behavior, and poisoning may occur.
Pearls & Pitfalls
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Not all poisonous plants are unpalatable, and they are not restricted to overgrazed ranges and pastures. Furthermore, poisonous plants do not always kill or otherwise harm animals when consumed; the dose determines toxicity. Many plants can be either useful forage or toxic. For example, plants such as lupine and greasewood may be part of an animal’s diet, and the animal is poisoned only when it consumes too much of the plant too fast. To prevent poisoning, it is important to understand the factors involved when a useful forage becomes a poisonous plant.
Poisonous Range Plants of Temperate North America
Scientific and common names | Habitat and Distribution | Affected Animals | Important Characteristics | Toxic Principle and Effects | Comments and Treatment |
|---|---|---|---|---|---|
Dangerous Season: Spring and Fall | |||||
Allamanda cathartica, A blanchettii (Apocynaceae) Allamanda, Yellow allamanda, Golden trumpet, Purple allamanda | Native to tropical America (2 cultivated taxa in North America); indoors and as ornamentals. | Sheep, cattle, and goats | Perennial, evergreen shrub, climbing; leaves simple, whorled; leathery, margins entire, axillary glands at base; large showy yellow or purple petal flowers; fruit is spiny capsule with numerous winged seeds. | The entire plant contains alkyliridoid-type terpenoids (allamandin, allamandacin), iridioids plumericin and plumieride, and little cardiotoxin. GI irritants in all parts (highest concentrations in the sap and roots). On ingestion, causes excess salivation, ruminal atony, abdominal cramps, diarrhea, dehydration, and electrolyte imbalance. Little cardiotoxic effect and no deaths. | Supportive, antidiarrheals |
Cicuta spp Water hemlock | Open, moist to wet environments; throughout North America | All | White flower, umbels. Veins of leaflets ending at notches. Stems hollow except at nodes. Tuberous roots from chambered rootstock. | Resinoids (cicutoxin, cicutol) in roots, stem base, young leaves. Toxicity retained when dry, except in hay. Rapid onset of clinical signs, with death in 15–30 min. Salivation, muscular twitching, dilated pupils. Violent seizures, coma, death. Poisoning in humans common. | Sedatives to control spasm and heart action. Prognosis good if alive 2 h after ingestion. |
Hymenoxys odorata Bitter rubberweed | Roadways, lake beds, flooded areas, overgrazed range; southwestern US | Sheep, rarely cattle | Multibranched annual or perennial up to 60 cm high. Yellow flower head. Leaves divided into narrow glandular segments. | Sesquiterpene lactone (hymenovin) in fresh or dry plant. Salivation, vomiting, green nasal discharge, listlessness, anorexia, abdominal pain. Lesions include inflammation of GI tract, foreign body pneumonia, renal degeneration. | Toxin cumulative. Avoid overgrazing. Remove from pasture. |
Hymenoxys richardsonii Pingue, Colorado rubberweed | Arid foothills (1,800–2,400 m; western US | Sheep, cattle, goats | Perennial herb. Leaves bright green, divided into narrow glandular segments. | Same as for H odorata (above). | Same as for H odorata. |
Oxalis spp, O corniculata (Oxalidaceae) Wood sorrel, Creeping lady’s sorrel, Creeping yellow wood sorrel | Herb or ornamentals found as weeds, growing from rhizomes/bulbs in fields or grazing pasture; worldwide | Sheep, rarely cattle | Annual or perennial with palmately compound leaves with 3 leaflets on erect or ascending stem. Inflorescence cymes or umbel or solitary flower; fruits are capsules with many seeds. | High oxalate contents throughout. Acute, subacute, or chronic signs after chronic ingestion. Clinical signs—progression from listlessness, weakness, labored respiration to prostration, coma, and death in 1–2 days in acute cases. Chronic cases—weight loss, anorexia, polyuria, edema, increased BUN and creatinine concentrations, failure to concentrate urine, presence of oxalate crystals in urine sediments, and renal failure. | Parenteral calcium solution. Supportive care to allow for tubular regeneration. |
Zephyranthes atamasca (Amaryllidaceae) Atamasco lily, Rain lily, Zephyr lily, Easter lily | Ornamental, commonly grows from bulbs in low woods and wet meadow areas. | Horses, cattle, and indoor pets (cats) | Basal leaves with star-shaped white flowers turning pink on fading. | Phenanthridine (lycorine, tazettine) and other alkaloids primarily in the bulbs but also in the leaves and flowers. Anticholinergic-type effects (inhibitor of protein synthesis, decreases heart rate, and cardiac abnormalities) in cats. Vomiting, excess salivation, bloody diarrhea (dehydration and electrolyte imbalance), seizures, cardiac function changes, and dermatitis. | Prompt resolution of dermatologic signs with discontinued exposure. Supportive care—antiemetics, antidiarrheals, and electrolyte replacement. Rarely lethal. |
Dangerous Season: Spring | |||||
Baptisia spp (Papilionoideae, Leguminosae, Fabaceae) False indigo, Wild indigo, Rattle weed, Yellow indigo, Indigo weed | Open woods in eastern North America on clay, loam, and sandy soils | Horses, cattle, goats | Herbaceous perennials, branched solitary stem, palmately compound sessile or short petiole, 3-leaflet leaves; terminal or axillary raceme inflorescence. Flowers with variably colored petals; legumes stipitate with one to many seeds. Plants black-gray or silvery gray when dry in the field or as hay. | Contains quinolizidine alkaloid cytisine, pyridine alkaloids anagyrine and baptifoline, and other related nicotine-like alkaloids. Interact with nicotinic, muscarinic, and acetylcholinergic receptors. On ingestion, causes severe diarrhea in cattle, decreased appetite, excess salivation, incoordination, and tremors. Fetal anomalies can be produced. | Remove animals from plant source. Supportive care. |
Caesalpinia spp (Leguminosae) Nikals, Gray nicker bean | Grown in the tropics in dry, open shrub or lowland rain forest. Found in southwestern US. Ornamentals cultivated in warmer areas. | Cattle, sheep, probably horses | Perennial tree, shrub, or herb armed with thorns, erect or climbing stem, 2 pinnately compound leaves, terminal racemes, showy yellow to orange or red flowers, legumes ovate with 2 to many seeds. | Gallotannins (30%–50%), phytohemagglutinins in fruit and flowers, and diterpenoids pulcherralpin and caesalpin in the leaves. Within a few hours of ingestion, patients show vomiting, with or without bloody diarrhea, abdominal discomfort, and dehydration. Not reported to cause death. | Supportive care—IV fluids, electrolytes, antiemetics, and antidiarrheals. |
Nolina texana Sacahuista, Beargrass | Open areas on rolling hills and slopes; southwestern US and Mexico | Cattle, sheep, goats | Perennial with many clustered, long narrow leaves. Stem mostly underground. Several flower stems with many small, white flowers in clusters. | Unidentified hepatotoxin (buds, flowers, fruit). Photosensitization, anorexia, icterus, prostration. Dark urine, yellowish discharge from eyes, nostrils. Lesions include hepatic and renal degeneration, GI inflammation. | Remove animals from area where plant grows during blooming season. Zinc oxide (not zinc sulfate) supplementation (30 mg/kg body wt, q 24 h) appears promising. |
Peganum harmala African rue | Arid to semiarid ranges; western US | Cattle, sheep, probably horses and camels | Multibranched, leafy, perennial, bright green, succulent herb. Leaves divided. Flowers white, single. | Related beta-carboline indole alkaloids (seeds, leaves, stems; seeds more toxic). Anorexia, hind leg weakness, knuckling of fetlock joints, listlessness, excess salivation, subnormal temperature, pollakiuria. Lesions include gastroenteritis, with hemorrhages on heart and under liver capsule. | Unpalatable. Eaten only under drought conditions. General supportive care most helpful. |
Phytolacca americana Pokeweed, Poke | Disturbed rich soils such as recent clearings, pastures, waste areas; eastern half of US | Pigs, cattle, sheep, horses, humans | Tall (up to 3 m), glabrous, green, red-purple, perennial herbs. Berries black-purple, staining, in drooping racemes. | Oxalic acid, a saponin (phytolaccatoxin), and an alkaloid (phytolaccin) in all parts; roots most toxic. Vomiting, abdominal pain, bloody diarrhea, hemolytic anemia, drop in production (dairy cattle). Terminal seizures, death from respiratory failure. Lesions include ulcerative gastritis, mucosal hemorrhage, dark liver. | No specific remedy for intoxication. Supportive care helpful. Monitor for hypotension and other cardiac effects. Oils and protectants (GI tract). Dilute acetic acid PO, stimulants. Blood transfusion (hemolytic anemia). |
Quercus spp Oaks | Most deciduous woods; throughout North America | All grazing animals, mostly cattle | Mostly deciduous trees, rarely shrubs, with 2–4 leaves clustered at tips of all twigs. Diverse leaf shape. Acorn fruiting body. | Gallotannin thought to be the toxin (young leaves and swollen or sprouting acorn). Anorexia, rumen stasis, constipation, followed by dark tarry diarrhea, dry muzzle, frequent urination, rapid weak pulse, death. Lesions include perirenal edema, nephrosis, gastroenteritis. | Diet must consist of > 50% oak buds and young leaves for a period of time. Increased BUN concentration with diet history diagnostic. Supportive care. Oral administration of ruminatorics helpful. See also Quercus Poisoning. |
Sarcobatus vermiculatus Greasewood, Black greasewood | Alkaline or saline bottom soils, not in higher mountains; arid west. Dangerous season spring; may be year-round. | Sheep, cattle | Large deciduous shrub with spiny stems. Fleshy, alternate, round in cross-section. Flowers inconspicuous. | Oxalates (sodium and potassium) 10%–15% dry weight (leaves primarily, less so in stems and fruits). Dyspnea, weakness, listlessness, some salivation, atony of GI tract, coma, death (neurologic effects and renal failure). Hyperkalemia, hypocalcemia, increased BUN concentration. Lesions include hemorrhage and edema of rumen wall, ascites, swollen kidneys (renal tubular necrosis and dilation). | Toxic when large quantity consumed in short time. Do not allow hungry animals to graze plant. Parenteral calcium solution offers temporary relief but relapses. |
Xanthium spp Cocklebur | Fields, waste places, exposed shores of ponds or rivers; throughout North America. Dangerous season spring and occasionally fall. | All animals, more common in pigs | Coarse annual herb. Fruit covered with spines, 2-beaked, with 2 compartments. | Carboxyatractyloside (seeds and young seedlings). Anorexia, listlessness, nausea, vomiting, weakness, rapid weak pulse, dyspnea, muscle spasms, seizures. Lesions include GI inflammation, acute hepatitis, nephritis. | Seedlings or grain contaminated with seeds. Oils and fats PO may be beneficial; parenteral glucose and bicarbonate are reported helpful; warmth, stimulants IM. |
Zigadenus spp Death camas, Meadow death camas, Grassy death camas | Foothill grazing lands, occasionally boggy grasslands, low open woods; throughout North and Central America | Sheep, cattle, horses | Perennial, bulbous, unbranched herbs with basal, flat, grasslike leaves. Flowers greenish, yellow, or pink; in racemes or panicles. No onion odor. | Cevanine-type veratrum azasteroid alkaloids, steroidal alkaloids, glycoalkaloids, and ester alkaloids (all parts). Salivation, vomiting, muscle weakness, ataxia or prostration, fast weak pulse, coma, death (central respiratory depression). No distinctive lesions. | Seeds most toxic. Leaves and stems lose toxicity as plant matures. Atropine sulfate and picrotoxin SC. |
Dangerous Season: Spring and Summer | |||||
Aesculus spp Buckeye | Woods and thickets; eastern US and California | All grazing animals | Trees or shrubs. Leaves opposite and palmately compound. Seeds large, glossy brown, with large white scar. | Glycoside, aesculin; also alkaloids and saponins in all parts, especially seeds and leaves. Listlessness, incoordination, twitching, paralysis, inflammation of mucous membranes. | Young shoots and seeds especially poisonous. Treatment only in severe cases. Stimulants and purgatives. Prevent access to toxic plant. Recovery in days. Rarely fatal. |
Amianthium muscaetoxicum Fly poison, Staggergrass, Crow poison, Gray fly poison | Open woods, fields, and acid bogs; eastern US | All grazing animals | Bulbous perennial herb. Leaves basal, linear. White flowers in a compact raceme, the pedicels subtended by short, brownish bracts. | Unidentified alkaloid, similar to those with Zigadenus (all parts). Salivation, vomiting, rapid and irregular respiration, weakness, death from respiratory failure. | No practical treatment. Especially dangerous for animals new to pasture. Keep animals well fed. |
Delphinium spp Larkspurs | Either cultivated or wild, usually in open foothills or meadows and among aspen; mostly western US. Dangerous season spring and summer; also seeds in fall. | All grazing animals, mostly cattle; sheep are somewhat resistant. | Annual or perennial erect herbs. Flowers each with 1 spur, in racemes. Perennial with tuberous roots. Leaves palmately lobed or divided. | Polycyclic diterpenoid alkaloids (eg, delphinine) in all parts, fresh or dry. Straddled stance, arched back, repeated falling, forelegs first. Constipation, bloat, salivation, vomiting. Death from respiratory and cardiac failure. Most often no lesions. | Young plants and seeds more toxic. Toxicity decreases with maturity. Antidote physostigmine (rather than atropine). |
Descurainia pinnata Tansy mustard | Dense stands, especially in wet years; arid southwestern US | Cattle | Annual to 60 cm tall, stem and leaves covered with fine pubescence. Leaves alternate, deeply pinnately dissected. Inflorescence on elongated raceme. Flower small with 4 spreading yellow to yellow-green petals. Fruit is copula with 2 carpels and long waxy seeds in 2 rows. | Toxic principle unknown; must be grazed over relatively long period. Partial or complete blindness, inability to use tongue or swallow, “paralyzed tongue,” “blind staggers,” wandering, head pressing, emaciation, death if not treated. | Administer water (8–12 L with stomach tube q 12 h). Include nourishment if patient weak. Prognosis good if treatment started early. Possibly mustards cause same condition. |
Lantana spp Lantana | Ornamentals and wild; in lower coastal plain of southeast US, and southern California | All grazing animals except horses | Shrubs. Young stems 4-angled. Leaves opposite. Flowers in flat-topped clusters, yellow, pink, orange, or red. Berries black. | Triterpenes (lantadene A and B) and unknowns in all parts, especially leaves and green berries. Anorexia, jaundice, watery feces, photosensitization. Lesions include degenerative changes in liver and kidneys. Death due to liver insufficiency, renal failure, myocardial damage. | Remove plants from pasture (herbicide 2,4-D susceptible). Keep patients out of light sources after eating plant. |
Senna obtusifolia Coffeepod, Sicklepod | Found in cultivated (corn, soybean, or sorghum) and abandoned fields, along fences, roadsides; naturalized in eastern US | All grazing animals, mostly cattle; also poultry | Annual shrub frequently found in same fields as S occidentalis. Distinguishing features include leaflets fewer in number and more rounded. Seed pods long, round to 4-sided, and more curved. Seeds shiny, brown, and rhomboid. | Toxic principles thought to be same as in S occidentalis. Clinical signs, although similar, less severe with S obtusifolia. | Treatment ineffective in down patients; salvaging most economic. Heat labile toxins not known to persist as residue. Meat from affected animals should be safe for human consumption. |
Senna occidentalis Coffee senna, Coffee weed, Styptic weed, Wild coffee | Common along roadsides, waste areas and pastures; naturalized in eastern US | Cattle, horses, chickens, goats, sheep, rabbits | Annual herb > 90 cm tall, with glandular, alternate pinnately compound leaves (8–12 ovate to lanceolate leaflets, terminal pair largest). Flowers are yellow, axillary, solitary, or in short racemes. Long, flat, straight to slightly curved pods with clearly outlined seed contents. Of the pods, seeds, and wilted foliage, seeds are most toxic. | Anthraquinones (emodinglycosides and oxymethylanthraquinone), chrysarobin and lectin (toxalbumins), and alkaloids are associated with GI dysfunction and myodegeneration. Afebrile, ataxic, with diarrhea and coffee-color urine, recumbent but eating and alert shortly before death. Increased serum creatine kinase and isocitric dehydrogenase activities; hyperkalemia and myoglobinuria frequent. Lesions include cardiac and skeletal muscle degeneration. Congestion, fatty degeneration, and centrilobular necrosis (liver) in addition to tubular degeneration (kidneys) also reported. Death probably due to hyperkalemic heart failure. | No specific treatment known. Supportive care essential. Although gross lesions similar to those of vitamin E/selenium deficiency, this treatment is contraindicated. Mineralocorticoid treatment may facilitate potassium excretion. Remove patients from source. Salvaging for economic reasons (see Senna obtusifolia, above). |
Tetradymia spp Horsebrush | Arid foothills and higher desert and sagebrush ranges, dense stands along trails; western US | Sheep | Shrubs with yellow flowers in spring, not later. Leaves spiny, silvery white. Early deciduous. | Furanoeremophilanes (tetradymol and others). Photosensitization, “bighead,” loss of hair and wool, skin ulcerations, blindness, secondary infections. Lesions include dermal necrosis and edema, hepatic and renal degeneration. Abortions may occur. | Photosensitization observed with concurrent ingestion of other green forages. Remove animals from plant source and sunlight. Antihistamines, topical antimicrobials, and parenteral corticosteroids beneficial. Recovery slow and possibly incomplete. |
Veratrum spp False hellebore, Skunk cabbage | Low, moist woods and pastures, and high mountain valleys; western US | Sheep, cattle | Erect herbs. Leafy throughout, leaves large and plaited. Flowers small and white or greenish. | Steroidal alkaloids. Vomiting, excess salivation, cardiac arrhythmia, bradycardia, dyspnea, muscle weakness and paralysis, coma, congenital cyclops in lambs from ewes exposed to V californicum. | Respiratory and heart stimulants. |
Dangerous Season: Summer and Fall | |||||
Acer rubrum Red maple | Moist land and swamps; eastern US | Horses | A large tree at maturity. Leaves opposite, 5–15 cm across, palmately 3- or 5-lobed each, roughly triangular, and coarsely toothed. Red to yellow polygamous flowers. Fruit, a pair of 1-seeded winged units connected at base. | Unknown toxic principle(s) in wilted leaves. Methemoglobinemia, Heinz body anemia, and intravascular hemolysis; weakness, polypnea, tachycardia, listlessness, icterus, cyanosis, brownish discoloration of blood and urine. | Not common. Methemoglobinemia a prognostic indicator. Isotonic fluids, oxygen, and blood transfusion can be helpful. Methylene blue treatment not rewarding. Early ascorbic acid treatment essential for recovery. |
Apocynum spp Dogbanes | Open woods, roadsides, fields; throughout North America | All | Erect, branching, perennial herb with milky sap arising from creeping underground root stock. Leaves opposite. Flowers white to greenish white in terminal clusters. Fruit long, slender, paired, with silky-haired seeds. | A resinoid and glucoside with some cardioactivity found in leaves and stems of green or dry plants. Increased temperature and pulse, dilated pupils, anorexia, discolored mucous membranes, cold extremities, death. | Supportive care with IV fluid therapy (cardiotoxin) and gastric protectants suggested. |
Centaurea repens Russian knapweed | Waste areas, roadsides, railroads, and overgrazed rangeland; not common in cultivated or irrigated pastures; mostly western and upper midwestern US | Horses | Perennial weed with slender rhizomes. Stems erect and well branched. Leaves pinnately lobed to entire, not spiny, narrowed basally but not petioled and of decreasing length up the plant. Thinly pubescent or glabrous. Blue, pink, or white flowers. One-seeded fruit with whitish, slightly ridged attachment scar. | Unidentified alkaloid in fresh or dried plant. Chronic exposure, acute onset of clinical signs. Inability to eat or drink, facial dystonia, chewing, yawning, standing with head down, severe facial edema, gait normal, head pressing, aimless walking or excitement most severe the first 2 days, become static thereafter. Death from starvation, dehydration, aspiration pneumonia. | More toxic than C solstitialis (below) but with similar pathology and prognosis. Some relief with massive doses of atropine but not an effective treatment. Euthanasia recommended. |
Centaurea solstitialis Yellow star thistle, Yellow knapweed | Waste areas, roadsides, pastures; mostly western US | Horses | Annual weed. Leaves densely covered with cottony hair. Terminal spreading cluster of bright yellow flowers with spines below. Branches winged. | Unidentified alkaloid. Involuntary chewing movements, twitching of lips, flicking of tongue. Mouth commonly held open. Unable to eat; death from dehydration, starvation, aspiration pneumonia. | Horses graze because of lack of other forage. Extended period of consumption essential for toxicity. Liquefactive necrosis of substantia nigra and globus pallidus (brain) pathognomonic. No treatment. Euthanasia recommended. |
Eupatorium rugosum White snakeroot | Woods, cleared areas, waste places, usually the moister and richer soils; eastern US | Sheep, cattle, horses | Erect perennial herb. Tremetol leaves, opposite, simple, serrated. Flowers small, white, and many. Often grows in large patches. | Complex benzyl alcohol (tremetol in leaves and stems). Excreted via milk; cumulative. Weight loss, weakness, trembling (muzzle and legs) prominent after exercise, constipation, acetone odor, fatty degeneration of liver, partial paralysis of throat, death in 1–3 days. | “Milk sickness” or “trembles.” Treatment nonspecific and supportive. Heart and respiratory stimulants and laxative may be necessary. Remove patient from access to plant, discard milk (hazardous to humans). |
Hypochaeris radicata Flatweed, Cat’s-ear, Gosmore | Native to the Mediterranean and South America; widely distributed in the US: Pacific states, eastern/southeastern | Horses | Perennial herb with viscid sap, stemless. Simple, serrated to lobed, basal, alternate leaves. One to several bright yellow flowers per plant. | Unknown; associated with but not proven cause of a neurologic condition in horses—stringhalt (hypermetria/hyperflexion of pelvic limb)—in dry years. Sudden onset of abnormal gait; flexion/delayed extension of hocks, knuckling of carpal joints,laryngeal hemiplegia; spontaneous recovery possible, but condition could be permanent. | Tranquilizers, sedatives, mephenesin, and thiamine (questionable effectiveness); longterm phenytoin treatment seems helpful. Treatment with baclofen also reported helpful. Surgery (pelvic tenotomy of the lateral digital extensors) reported helpful. |
Oxytenia acerosa, Iva acerosa Copperweed | Arid, alkaline soils in foothills, sagebrush plains; western US | Cattle, sheep | Tall, annual or perennial herb with narrow leaflets. Flowers in many heads resembling goldenrod. | Unknown (pseudoguaianolide sesquiterpene lactones found in species–-consistent clinical signs with these toxins); all above-ground parts, green or dry. Metabolic disease, anorexia, marked listlessness, weakness, coma; death without struggle within 1–3 days. | No specific treatment. Supplement diet or change pasture. |
Perilla frutescens Perilla mint, Beefsteak plant | Ornamental originally from India, escaped to moist pastures, fields, roadsides, and waste places; southeastern US | Cattle primarily, horses and other grazing animals susceptible | Annual, freely branched, squared stems. Opposite, purple or green, coarsely serrated leaves. White to purple flowers. Strong pungent odor when crushed. | Green or dry, 3-substituted furans (perilla ketone, egomaketone, isoegomaketone). Clinical signs 2–10 days after exposure include dyspnea (especially on exhaling), open-mouth breathing, lowered head, reluctance to move, death on exertion. Lesions include pulmonary emphysema and edema. | Treatment ineffective once clinical signs severe. Parenteral steroids, antihistamines, and antimicrobials may help. Handle gently (prevents exertion and death). Avoid or limit grazing during flowering and fruiting period. |
Prosopis glandulosa Mesquite | Dry ranges, washes, draws; southwestern US | Primarily cattle, also goats; sheep resistant | Perennial, deciduous shrub or small tree with smooth or furrowed gray bark, paired spines. Leaves divided. Legume pod long, constricted between seeds. | Unknown principle in the beans. Chronic wasting with rumen atony, excess salivation, continual chewing. Partial paralysis of tongue, facial muscle tremor, submandibular edema, anemia. Lesions include emaciation, small firm kidneys and liver, gastroenteritis, filled rumen. | High sucrose content of beans alters rumen microflora, inhibiting cellulose digestion and B vitamin synthesis if grazed for extended period. |
Robinia pseudoacacia Black locust, False acacia, Locust tree | Open woods, roadsides, pinelands, on clay soils preferably; eastern US | All grazing animals, mostly horses | Tree or shrub. Deciduous, alternate, pinnately compound leaves (> 10 elliptic to ovate leaflets). Pair of spines at base of each leaf. Flowers in loose, fragrant, white to cream, drooping racemes. Flattened, brown pods containing 4–8 seeds. | The glycoside robitin, a lectin (hemagglutinin), and the phytotoxins robin and phasin found throughout plant, although flowers have been suggested as the toxic principles. Diarrhea, anorexia, weakness,hindquarters paralysis, listlessness, mydriasis, cold extremities; frequently laminitis and weak pulse. Death infrequent; recovery period extensive. Postmortem lesions restricted to GI tract. | Laxatives and stimulants suggested. Supportive care. |
Rumex crispus Curly dock, Dock, Sorrel | Commonly found on acid or sterile, graveled, seasonally moist soils of waste places, pastures, and fields throughout US | Cattle, sheep | Perennial herb with erect stems, 90–120 cm tall. Leaves alternate, lanceolate to elliptic, finely crisped margins, base obtuse to cuneate, petioles form sheath around stem. Flowers small, numerous, greenish, in long terminal panicles; fruit an achene, papery 3-winged, with lustrous brown seeds. | Oxalic acid and soluble oxalate in leaves, stem, and seeds. Acute course (hypocalcemia, labored breathing, anorexia, listlessness, muscle fasciculation, tremor, weakness, teeth grinding, pulmonary edema, tetany, seizure, recumbency, and prostration); subacute (hypocalcemia, altered kidney function) or chronic course (renal fibrosis, renal insufficiency, and urolithiasis). Hemorrhage, edema (rumen and abomasal walls), and ascites (intestinal mucosa) observed in toxic cases. Death resulting from shock and hemorrhagic rumenitis. | In acute cases, death is too rapid for any treatment. Supportive care can be helpful. Remove patients from source. Calcium IV to correct hypocalcemia is ineffective. Administer lime water to precipitate oxalate and prevent absorption. Allow animals to develop tolerance to oxalate by exposure to small amounts over time. Do not allow animals to graze pasture or offer hay highly contaminated with oxalate-producing plants. |
Solanum spp Nightshades, Jerusalem cherry, Potato, Horse nettle, Buffalo bur | Fencerows, waste areas, grain and hay fields; throughout North America | All | Fruits small; yellow, red, or black when ripe; structurally like tomatoes; clustered on stalk arising from stem between leaves. | Glycoalkaloid solanine (leaves, shoots, unripe berries). Acute hemorrhagic gastroenteritis, weakness, excess salivation, dyspnea, trembling, progressive paralysis, prostration, death. | Pilocarpine, physostigmine, GI protectants. Seeds may contaminate grain. |
Dangerous Season: Fall and Winter | |||||
Allium cepa, A canadense Onions (cultivated and wild) | Cultivated and grown on rich soils throughout US | Cattle, horses, sheep, dogs | Biennials and perennials, bulb plants, onion odor. Leaves basal, green, hollow, cylindrical (A cepa), lustrous green, flat (A canadense); flowers on hollow stalks, terminal umbels of many small blooms; fruits 3-celled capsules with many seeds. | N-propyl disulfide, an oxidant, in all parts. Anemia develops within days of exposure. Toxicosis in cattle associated with prolonged ingestion of large amounts of onions. N-propyl disulfide inhibits RBC glucose-6-phosphate dehydrogenase, leading to hemolysis and formation of Heinz bodies. Clinical signs are hemoglobinuria, diarrhea, loss of appetite, jaundice, ataxia, collapse, and possible death if untreated. Hemolytic anemia reported in production animals ingesting wild onions. Heinz body anemia; swollen, pale, necrotic liver; hemosiderin in liver, kidneys, and spleen are reported pathologic lesions. | Clinical signs similar to toxicity induced by S-methylcysteine sulfoxide (a rare toxic amino acid in Brassica spp) in production animals. Susceptibility to onion poisoning varies across animal species: cattle more susceptible than horses and dogs, which are more susceptible than sheep and goats. Remove animals from source and prevent future access to cull onions. Supportive care essential. |
Astrolepis cochisensis ssp. cochisensis Jimmy fern, Cochise scaly cloak fern | Dry rocky slopes and crevices, chiefly limestone areas; southwestern US | Sheep, goats, cattle | Evergreen from rhizomes, perennial, erect fern with divided leaves, folding when dry. Leaflets about as wide as long, scaly on back. | Unknown (excreted in milk). Nervous syndrome, incoordination, arched back, trembling, increased respiratory rate and pulse. Death when not allowed to rest. | No specific treatment. Supportive and general nursing care helps. Avoid driving during danger period. Provide ample watering, placed to avoid long walks. Allow rest if clinical signs occur. |
Daubentonia punicea Rattlebox, Purple sesbane | Cultivated and escaped, in waste places; southeastern US coastal plain | All | Annuals or perennials, shrub. Leaves pinnately compound with ≥ 20 leaflets. Flowers orange-red, rose, or purple. Legume pods (≥ 5 seeds) longitudinally 4-winged. | S punicea most toxic species (0.1% body wt toxic to sheep and cattle). Toxins not fully characterized, but saponins are primary suspects; 12–24 h delay in clinical signs after ingestion. Rapid pulse, weak respiration, diarrhea, death. | Supportive care; specific cause unknown. Seeds poisonous. Remove animal from source. Fluids and electrolytes for dehydration. |
Glottidium vesicarium Bladderpod, Rattlebox, Sesbane, Coffeebean | Mostly open, low ground, abandoned cultivated fields; southeastern US coastal plain | All | Tall annual. Legume pods flat, tapered at both ends, 2-seeded. Leaves pinnate, divided. Flowers yellow. | Unknown (green plant and seeds). In ruminants, hemorrhagic diarrhea, shallow rapid respiration, fast irregular pulse, coma, death. Lesions include hemorrhages in abomasum and intestines, dark tarry blood. | Green seeds are more toxic. Remove animal from source immediately. General supportive treatment—saline purgatives, rumen stimulants, IV fluid therapy. |
Halogeton glomeratus Halogeton | Deserts, overgrazed areas, winter ranges, alkaline soils; western US | Sheep, cattle | Annual herb. Leaves fleshy, round in cross-section, tip with stiff hair. Axillary flowers inconspicuous. Fruits bracted and conspicuous. | Oxalic acid, oxalate. Acute course. Rapid labored respiration, listlessness, weakness, coma, death. Lesions include hemorrhages and edema of rumen wall, swollen kidneys, oxalate crystals in kidneys and rumen wall. | Toxic dose consumed over short period. Increase water consumption. Standard treatment IV calcium borogluconate (helpful in cattle, delay deaths in sheep). Calcium supplement (83% alfalfa, 15% calcium carbonate, 2% molasses) in feed before grazing. Halogeton forage can be helpful. Herbicide 2,4-D control. |
Isocoma pluriflora (Haplopappus heterophyllus) Rayless goldenrod, Burroweed, Jimmyweed | Dry plains, grasslands, open woodlands, and along irrigation canals; alkaline soils; southwestern US and northern Mexico | Cattle, sheep, horses | Bushy perennial 60–120 cm tall, with many yellow flower heads. Leaves alternate, linear, sticky. | Complex benzyl alcohol (tremetol); resin acid; primarily nursing young and nonlactating animals. Reluctance to move, trembling, weakness, vomiting, dyspnea, constipation, prostration, coma, death. | “Milk sickness.” Treatment similar to E rugosum intoxication. Prevent access to plants (growing season). Remove young and discard milk (hazardous to humans). |
Juglans nigra Black walnut | Native to eastern US; now from eastern seacoast, west to Michigan and most of the Midwest, south to Georgia and Texas | Horses | Tree with deciduous, alternate, pinnately compound leaves (numerous lanceolate leaflets with serrated margins); leaflets in middle are largest. Male and female flowers on same tree but different inflorescences. Thick husked nut does not open when ripe. Twigs have chambered pith. | Juglone, phenolic derivative of naphthoquinone. Shavings with as little as 20% black walnut toxic within 24 h of exposure. Reluctance to move; listlessness; increased temperature, pulse, respiration rate, abdominal sounds, digital pulse, hoof temperature; distal limb edema; lameness. Severe laminitis with continued exposure. | Nonfatal; laminitis and edema of lower limbs. Remove shavings promptly (relief signs). Treat for limb edema and laminitis. Improvement in 24–48 h with no sequelae. NSAIDs are mainstay; prazosin, nifedipine are promising. Avoid corticosteroids (worsen existing vasoconstriction). |
Melilotus officinalis and M alba Sweet clover, White sweet clover | Commonly found on alkaline soils, fields, roadsides, and waste places; forage crop in southern and northern US | Most commonly cattle, also horses and sheep | Annual or biennial herb 1–2 m tall. Leaves alternate, pinnately compound with 3 obovate leaflets, serrated margins. Yellow or white flowers on racemes. Small 1-seeded pods. | See sweet clover poisoning content. | See sweet clover poisoning content. |
Sophora secundiflora Mescal bean, Coral bean, Sophora, Frijolito, Texas mountain laurel | Hills and canyons, limestone soils; southwestern Texas into Mexico | Cattle, sheep, goats | Evergreen shrub or small tree. Leaves alternate, divided, and leathery. Flowers violet-blue, fragrant. Seeds large and bright red with hard seed coat, in legume pod. | Quinolizidine alkaloid (seeds and probably leaves). Violent trembling, stiff gait, falling on exercise, recumbent for a few minutes, becoming alert and eating. | Supportive. Toxic effect not cumulative, consume large amounts quickly. Seeds more dangerous when crushed. |
Dangerous Season: Fall, Winter, and Spring | |||||
Melia azedarach Chinaberry | Fencerows, brush, waste places; southern US | Pigs and sheep, others (dogs) less susceptible | Small to medium deciduous tree. Fruit cream or yellow with a furrowed globose stone, persisting on tree through winter. Large amount required for intoxication. | Several alkaloids and a saponin (all parts), fruit most toxic. Restlessness, vomiting, constipation, cyanosis, rapid pulse, dyspnea, death within 24 h. | Gastroenteritis usual. Recovery may be spontaneous. Laxatives and GI protectants suggested. |
Dangerous Season: All Seasons | |||||
Acacia berlandieri Guajillo, Catclaw, Blackbrush, Acacia | Semiarid rangelands; southwestern Texas into Mexico | Sheep, goats | Deciduous shrub or small tree. Leaf divided. Flowers white to yellowish in dense heads. Fruit a legume with margins thickened. | Amine, N-methyl-beta-phenylethylamine. Chronic course. Ataxia of hindquarters (limberleg), marked excitation, prostration, remain alert, death from starvation. | Dominates vegetation in some areas. Valuable to sheep industry due to high nutritive value and dominance. Supplement during drought to decrease possibility of poisoning. |
Agave lechuguilla Lechuguilla | Low limestone hills, dry valleys, and canyons; southwestern US. Dangerous all seasons, especially spring. | Sheep, goats, cattle, usually during drought | Perennial, stemless, with thick, fleshy, tapered leaves having sharply serrated margins. Flowers infrequently with tall terminal panicle. | Unidentified hepatotoxin (causing photosensitivity) and a toxic saponin (abortifacient action). Subacute course. Listlessness, anorexia, icterus, yellow discharge from eyes and nostrils, photosensitization, coma, death. | Remove animals from range and provide shade. |
Agrostemma githago Corn cockle | Weed, grainfields, and waste areas; throughout North America | All | Green winter annual with silky-white hairs, opposite leaves, purple flowers, black seeds. | Saponin (githagenin) in seeds. Acute course. Profuse watery diarrhea, vomiting, listlessness, general weakness, tachypnea, hemoglobinuria, death. | Maintain hydration (fluids and electrolytes) and control diarrhea. Oils and GI protectants. Neutralize toxin (dilute acetic acid PO). Blood transfusions may be necessary. |
Asclepias spp Milkweeds | Dry areas, usually waste places, roadsides, streambeds, western US | All | Perennial erect herbs, shrubs, vines, or small trees with milky sap. Leaves simple, opposite or whorled with entire margins. Seeds silky-hairy from elongated pods. | Steroid glycosides and toxic resinous substances (all parts), green or dry. Staggering, tetanic seizures, bloating, dyspnea, dilated pupils, rapid and weak pulse, coma, death. | Sedatives, laxatives, and IV fluids suggested. Prevent plant consumption. Do not feed milkweed-contaminated hay. |
Astragalus spp, Oxytropis spp (certain species only) Locoweed | Mostly western US | All grazing animals | Stemmed or stemless perennial herbs. Leaves alternate and pinnately compound. Flowers leguminous. Chronic intoxication. | Swainsonine. Listlessness, emaciation, incoordination, dry lusterless hair. Abortions. Neurovisceral cytoplasmic vacuolation, congestive right heart failure in cattle grazing at high altitudes. | Avoid grazing of source. Both green and dry plants toxic. |
Astragalus spp (certain species only) Milkvetch, etc (many common names) | Nearly all | All grazing animals | Stemmed or stemless perennial herbs. Leaves alternate and pinnately compound. Flowers leguminous. Chronic intoxication. | Miserotoxin, other aliphatic nitro compounds. Hindquarters paralysis, goose-stepping, listlessness, rough coat, pulmonary emphysema, acute death, cord demyelination. | Avoid grazing of preflower stage. |
Astragalus spp (certain species only—selenium accumulators) Many common names | Seleniferous areas, mostly western and midwestern US | All grazing animals | Stemmed or stemless perennial herbs. Leaves alternate and pinnately compound. Flowers leguminous. Chronic intoxication. | Selenium (chronic). Slow growth, reproductive failure, loss of hair, sore feet, acute death. | Avoid grazing seleniferous plants for extended periods. See selenium toxicosis content. |
Baccharis spp Silverling, Baccharis, Yerba-de-pasmo | Open areas, often moist; southeastern and southwestern US | Cattle | Shrubs. Numerous small, whitish flowers. Leaves resin-dotted and persistent southward. | Unidentified. Acute course. Rumen stasis, bloat, anorexia, excess salivation, diarrhea, staggering, trembling, restlessness, polypnea, tachycardia, death. | Most dangerous in early growing stage. Toxin concentrated in leaves and flowers. No specific treatment. Treatment toward relief of diarrhea is best. |
Brassica spp, Raphanus spp, Descurainia spp, Berteroa incana Mustards, Crucifers, Cress; and for B incana, Hoary alyssum, Hoary false alyssum | Fields, waste areas, hay meadows, roadsides; throughout North America | Cattle, horses, pigs | Annual/biennial herbaceous weeds with terminal clusters of yellowish flowers and slender, elongated seed pods. | Glucosinolates (isothiocyanate, thiocyanates, nitrites) in seeds and vegetative parts, fresh or dry. Acute or chronic course. Anorexia, severe gastroenteritis, salivation, diarrhea, paralysis, photosensitization, hemoglobinuria. Unknown toxic principle in B incana causes rapid onset of transient distal limb edema, laminitis (horses), and severe GI disturbances with continued exposure. Late abortions or weak, premature foals at birth. | No specific treatment (B incana disease in horses). Phenylbutazone, flunixin, furosemide or other diuretics helpful in relieving pain, inflammation, and edema. Remove from source. Administer GI protectants (mineral oil). |
Cestrum diurnum, C nocturnum Day-blooming jessamine and night-blooming jessamine, respectively | Open woods and fields; Gulf Coast states (Florida, Texas) and California | Cattle, horses, and dogs (ingesting cholecalciferol-based rodenticides) | Evergreen shrubs or tall bush; leaves alternate, ovate smooth-edged; flowers white, tubular, small clusters, fragrant by day; fruit, a greenish-white to lavender (immature), becoming dark purple to black (mature), fleshy berry, with several small, black, oblong seeds, dispersed by birds in droppings. Leaves longer, night fragrant flowers, white fruits at maturity (C nocturnum). | Atropine-like alkaloids (fruit), saponins (fruit and sap), and glycosides of 1,25-dihydroxycholecalciferol (leaves primarily, stem, fruits, and roots) are found. Gastroenteritis develops on ingestion of fruits. Vomiting, listlessness, anorexia, chronic weight loss with normal appetite, choppy stiff gait, increased pulse, persistent hypercalcemia and hyperphosphatemia, calcinosis (aorta, carotid and pulmonary arteries, tendons, ligaments, and kidneys). Parathyroid atrophy, thyroid (C-cell) hypertrophy, and osteopetrosis reported with chronic ingestion of leaves. | Prevent further access of animals to plants. In early stages, treatment might be effective and cost-effective. Correct fluid and electrolyte imbalances in cases with persistent vomiting or diarrhea. Decrease or prevent hypercalcemia (calciuresis, diuretics, steroids, calcitonin). Maintenance treatment of diuretics and steroids may be necessary. |
Conium maculatum Poison hemlock | Roadside ditches, damp waste areas; throughout North America | All | Purple-spotted hollow stem. Leaves resemble parsley, parsnip odor when crushed. Taproot. Flowers white, in umbels. | Piperidine alkaloids (coniine and others) in vegetative parts. Acute course. Dilated pupils; weakness; staggering gait; slow pulse, progressing to rapid and thready. Slow, irregular breathing; death from respiratory failure. Teratogenic in cattle. | Coniine excreted via lungs and kidneys, mousy odor of breath and urine diagnostic. Administer saline cathartics; neutralize alkaloids with tannic acid, together with stimulants. |
Crotalaria spp Crotalaria, Rattlebox | Fields and roadsides; eastern and central US | All | Annual or perennial legume. Yellow flowers in racemes, pods inflated. Bracts at base of pedicels of flowers and fruits persistent. Leaves simple or divided. Seeds in harvested grain. | Pyrrolizidine alkaloid (monocrotaline) and other unidentified alkaloids (all parts, especially seeds). Chronic course. Chickens: diarrhea, pale comb, ruffled feathers; horses: unthriftiness, ataxic, walking in circles, icterus; cattle: bloody diarrhea, icterus, rough coat, edema, weakness. Death may occur from a few weeks to months after ingestion. | Cumulative, fresh or dry. No treatment. |
Cynoglossum officinale Hound’s tongue | Common in waste places, roadsides, and pastured areas throughout US | Cattle, sheep, horses | Annual or biennial herbaceous plant, rough hairy stem and foliage,90–120 cm tall. Leaves alternate, oblanceolate, narrowed to petiole (lower), lanceolate, sessile, clasping (upper). Flowers numerous in coiled racemes, without bracts, blue, purple, or white blooms. Fruit, burrlike from 4 nutlets, thickly covered with hooked prickles. | Pyrrolizidine alkaloids (0.6%–2.1% of dry matter) including heliosupine and echinatine in the foliage. Unpleasant odor discourages consumption when fresh, becomes palatable in hay and is readily consumed. Toxic insult primarily hepatic and chronic in nature. Pyrrolizidine alkaloids (inactive) undergo hepatic metabolization to active intermediates—pyrroles (alkylating agent), which are toxic. Clinical signs are anorexia, listlessness, rough coat, hemorrhage, tenesmus, bloody feces, ataxia, jaundice, death. Hepatic lesions of necrosis, edema, megalocytosis, bile duct hyperplasia, and cytoplasmic vacuolation reported. | Know source and quality of hay. Supportive care. Affected animals seldom recover. |
Datura stramonium Jimson weed, Thorn apple | Fields, barn lots, trampled pastures, and waste places on rich bottom soils; throughout North America | All | Leaves wavy. Flower large (10 cm), white, tubular. Fruit a spiny pod, 5 cm long. | Tropane alkaloids (atropine, scopolamine, hyoscyamine) in all parts, seeds in particular. Acute course. Weak rapid pulse and heartbeat, dilated pupils, dry mouth, incoordination, seizures, coma. | All parts, mainly in hay or silage. Urine from animal dilates pupils of laboratory animals (diagnostic). Treatment nonspecific; cardiac and respiratory stimulants (physostigmine, pilocarpine, arecoline). |
Drymaria pachyphylla Inkweed, Thickleaf drymary | Heavy alkaline clay soil in low areas or dry, overgrazed pastures; southwestern US | Cattle, sheep, goats | Multibranched, succulent, prostrate annual. Opposite or whorled appearing leaves. Small white flowers. | Problem in heavily overgrazed areas. Unknown toxic principle. Sudden onset of diarrhea, restlessness, listlessness, coma, death. Lesions include gastroenteritis with congestion of liver, kidneys, spleen. Petechial hemorrhages on heart. | Dangerous during drought, after rain, or at night. Avoid overstocking to improve range. In well-fed and watered animals, little or no problem observed. Poor response to treatment. |
Festuca arundinacea Tall fescue | A coarse, hardy, drought-resistant grass; Pacific Northwest, Missouri, Oklahoma, and Kentucky; major pasture grass in southeastern US | Mostly cattle and horses | Coarse, deeply rooted perennial grass. Broad, dark-green, ribbed, rough upper surface, and smooth sheathed leaves. Grows in clumps. | See fescue poisoning section. | See fescue poisoning content. |
Gelsemium sempervirens, G rankinii Yellow jessamine, Evening trumpet flower, Carolina jessamine | Open woods, thickets, swamps, low areas, and open fields; southeastern US | All | Climbing or trailing vines. Evergreen, entire, opposite leaves. Yellow tubular flowers, very fragrant. | Potent neurotoxic alkaloids (gelsemine and others, related to strychnine) in all parts; gelsemine the most toxic. Acute course. Weakness, incoordination, dilated pupils, seizures, coma, death within 48 h. Limberneck in fowl. Clinical signs indicative of a poor prognosis. | No specific treatment. Relaxants and sedatives suggested. PO administration of strong tea or coffee or poison hemlock on early exposure (before observation of clinical signs) seems helpful in decreasing further toxin absorption (more basic stomach pH). |
Gutierrezia microcephala Threadleaf, Snakeweed, Small-head matchweed, Sticky snakeweed | Widespread over dry range and desert; primarily southwestern US | Cattle, sheep, goats, pigs | Multibranched, perennial, resinous shrub. Simple leaves, alternate; yellow-flowered heads. | Unknown. Steroidal effect of saponins, mono- and diterpene acids. Acute toxicosis, anorexia, listlessness, hematuria, diarrhea followed by constipation. In cattle, abortions with retained placenta, stillbirths, or premature and weak calves. | No specific treatment. Supplementing diet will help but not entirely prevent abortion in cattle. |
Helenium hoopesii Orange sneezeweed | Moist slopes and well-drained mountain meadows; abundant in overgrazed areas; western US | Sheep, rarely cattle | Annuals, biennials, perennial herb. Orange sunflower-like heads or yellow flowers. Leaves alternate. | Sesquiterpene lactones (helenalin, hymenoxon). Subacute course (spewing sickness). Listlessness, weakness, restlessness, stiff gait, salivation, pronounced vomiting, emaciation, eventual death. | Cumulative. Aspiration pneumonia frequent. Remove from access to plant. Graze sneezeweed areas for only short periods of time. Can graze intermittently with some success. |
Helenium microcephalum Small head sneezeweed | Moist ground; southern US | Cattle, sheep, goats | Annual, erect herb, simple-stemmed below, bushy above. Stem winged. Narrow leaves throughout. Flowers in small heads; disk pale red-brown, rays yellow. | Sesquiterpene lactone (helenalin) in flowering stage. Listlessness, weakness, restlessness, stiff gait, salivation, vomiting. | Cumulative. Remove from pasture. Cathartics may help. |
Hypericum perforatum St. John’s-wort, Goatweed, Klamath weed | Dry soil, roadsides, pastures, ranges; throughout North America | Sheep, cattle, horses, goats | Perennial herb or woody below. Leaves simple, opposite or whorled, dotted. Flowers many, yellow, with many stamens. | Photodynamic pigment (hypericin). Subacute course. Photosensitization, pruritus and erythema, blindness, seizures, diarrhea, hypersensitivity to cold water contact, death. | Remove animals from source and sunlight. Corticosteroids parenterally, topical broad-spectrum antimicrobials. |
Kalmia spp Laurel, Ivybush, Lambkill | Rich moist woods, meadows, or acid bogs; eastern and northwestern US. Dangerous all seasons, especially winter and spring. | All, often sheep | Woody shrub. Evergreen, glossy leaves. Flowers pink to rose, showy. | Resinoid (andromedotoxin) and a glucoside (arbutin) in vegetative parts. Acute course. Incoordination, excess salivation, vomiting, bloat, weakness, muscular spasms, coma, death. | Undigested rumen contents and ingesta in lungs at necropsy. Laxatives, demulcents, nerve stimulants, atropine. |
Kochia scoparia Kochia, Burning bush, Fireball, Fireweed, Poor man’s alfalfa | Throughout North America | Cattle, sheep | Annual to 1.5 m tall. Many branched stems give bushy appearance. Leaves petiolate, lanceolate, thin, and flat; alternate. Fruit has 5 wedge-shaped wings. | An alkaloid has been suggested. This plant may also accumulate nitrate and oxalate. Disease syndromes: photosensitization, weight loss, and polioencephalomalacia, which seems intensified by slow growth and sulfates. | Harvested foliage is source of toxin. Protect from sun in case of photosensitization; treat polioencephalomalacia with vitamin B. Supplement with copper (preventive against polioencephalomalacia). |
Ligustrum spp Privet, Ligustrum, Hedge plant | An ornamental; common as hedge; found at abandoned farm home sites, along fences, and in bottomlands; eastern US | All production animals | Shrubs up to 5 m tall. Simple, opposite, short-petioled, evergreen or deciduous leaves. Numerous small, white flowers in panicles. Fruit is 1- to 2-seeded, black or dark blue berry that persists throughout winter. | Ligustrin, ligustron, syringin, syringopicrin, and other unknown compounds in leaves and fruit. Primarily GI irritants. Diarrhea, abdominal pain, incoordination, paresis, weak pulse, hypothermia, seizures, sometimes death. | Supportive care; correct dehydration. |
Lupinus spp Lupines, Silky lupine, Sink lupine, Bluebonnet | Dry to moist soils, roadsides, fields, and mountains; throughout, but poisoning mostly in western US | Sheep, cattle, goats, horses, pigs | Perennials. Leaves simple or palmately divided. Flowers blue, white, red, or yellow in terminal raceme. | Quinolizidine alkaloids (20 known) concentrated in seeds (fresh and dry); some piperidine alkaloids. Acute course. Inappetence, dyspnea, struggle, seizures, death from respiratory paralysis. Lupinosis (hepatotoxicosis) not a reported problem in the US. Some species teratogenic in cattle (crooked calf disease, weak and deformed calves, stillbirths). | Do not disturb sick patients; remove from source as they begin to recover. No effective treatment, but survivors recover completely. See mycotoxic lupinosis section. |
Nandina domestica Nandina, Heavenly bamboo, Chinese sacred bamboo | Common ornamental in southern US | All grazing animals, especially ruminants | Upright, unbranched, and multistemmed evergreen shrub, 1–2 m tall. Alternate, bi- to tripinnately compound leaves; leaflets subsessile, elliptic-lanceolate, half as wide as long, entire, leathery, metallic bluish-green becoming purple in fall. Small, white flowers; 2-seeded, bright red berries in large panicles persist throughout fall and winter. | Cyanogenic glycosides in foliage and fruits, hydrolyzed in GI tract to free cyanide, thereby affecting cellular respiration. See cyanide poisoning section. Prognosis good if patient survives for 1 h after clinical signs begin. | Acute outcome precludes effective treatment for most; IV sodium nitrite/sodium thiosulfate treatment of choice. Picrate test indicates toxic potential of the plant. See cyanide poisoning content. |
Nerium oleander Oleander, Laurel rosa, Laurel blanco | Common ornamental in southern regions of US | All | Evergreen shrub or tree. Leaves whorled and prominently, finely, pinnately veined beneath. Flowers showy, white to deep pink. | Digitoxin-type glycosides (oleandroside, nerioside, and others) in all parts, fresh or dry. Acute course. Severe gastroenteritis, vomiting, diarrhea, increased pulse rate, weakness, death. | No specific treatment. Atropine in conjunction with propranolol reported helpful. |
Photinia fraseri, P serrulata, P glabra Fraser’s photinia, Chinese photinia, Red leaf photinia, Red tip photinia | Common ornamental (hedge or screen) in southern US | All grazing animals, mostly ruminants | Evergreen shrubs, 3–5 m tall. Alternate, oblong-ovate serrated leaves, copper-red (when young) turning dark green in 2–4 wk. Prominent, whitish flowers in spring; showy, red berries in fall. | Cyanogenic glycosides in foliage and fruits, hydrolyzed in GI tract to free cyanide, thereby affecting cellular respiration. See cyanide poisoning section. Prognosis good if patient survives for 1 h after clinical signs begin. | Acute outcome precludes effective treatment for most; IV sodium nitrite/sodium thiosulfate treatment of choice. Picrate test indicates toxic potential of the plant. See cyanide poisoning content. |
Pinus ponderosa Ponderosa pine, Western yellow pine | Coniferous forests of Rocky Mountains at moderate elevations; western US. Dangerous all seasons, especially winter. | Cattle. Sheep and deer seem not to be affected. | Evergreen tree, 46–55 m. Leaves in groups of 3, yellowish green, 18–28 cm long. Small soft cones, seeds mature in 2–3 yr. Bark platy, reddish orange. | Unknown toxic principle (diterpene esters of isocupressic acid are suspected). Chronic course. Abortions in late gestation, stillbirths or weak calves, depressed, edema of vulva and udder, retained placenta. | Pine-needle ingestion during last half of gestation—may abort after single exposure. Supportive care, remove retained placenta, treat metritis, provide good nutrition. Keep pregnant cows away from source. |
Prunus caroliniana Laurel cherry, Cherry laurel, Mock orange | Woods, fencerows, and often escaped from cultivation; southern regions. Dangerous all seasons, especially winter and spring. | All grazing animals | Leaves evergreen, shiny, leathery. Broken twigs with strong cherry bark odor. Fruit black. | Hydrocyanic acid (wilted leaves, bark, and twigs). Peracute course. Difficult breathing, bloat, staggering, seizures, followed by prostration and death. Mucous membranes and blood bright red. | See cyanide poisoning content. |
Prunus spp Chokecherries, Wild cherries, Peaches | Waste areas, fencerows, woods, orchards, prairies, dry slopes | All grazing animals, mostly cattle and sheep | Large shrubs or trees. Flowers white or pink. Cherries or peaches. Crushed twigs with strong odor. | Glycoside-yielding cyanide (rumen hydrolysis). Excitement leading to listlessness, dyspnea, incoordination, seizures, prostration. Death may occur in 15 min from asphyxiation. | Mucous membranes, bright pink color; blood, bright red color. See cyanide poisoning content. |
Psilostrophe spp Paperflowers | Open range lands and pastures; southwestern US | Sheep primarily; cattle and goats less susceptible and less likely to eat the plant. | Perennial composite. Erect, woolly stems branching from base. Leaves simple, alternate, petioled. Many small heads of yellow flowers. | Sesquiterpene lactone. Listlessness, incoordination, anorexia, weakness, trembling, rapid irregular pulse and respiration, coughing, vomiting, aspiration pneumonia, death. | Antimicrobial actions of sesquiterpene lactone in rumen affect metabolism. Supplement diet with sodium sulfate and high protein. |
Pteridium aquilinum Bracken fern, Bracken, Brake fern | Dry poor soil, open woods, sandy ridges, throughout North America | All grazing animals | Leaves firm, leathery, 3-pinnate. | ||
Ricinus communis Castor bean | Cultivated in southern regions | All | Large, palmately lobed leaves. Seeds resembling engorged ticks, usually 3 in somewhat spiny pod. | Phytotoxin—ricin in all parts (seeds especially toxic). Acute to chronic course (death or recovery). Violent purgation, straining with bloody diarrhea, weakness, salivation, trembling, incoordination. | Diagnosis based on presence of seeds, RBC agglutination, precipitin test. Specific antiserum, ideal antidote; sedatives, arecoline hydrobromide, followed by saline cathartics suggested. |
Senecio spp Groundsel, Senecio | Grassland areas; mostly western US | Cattle, horses, sheep to a limited extent in US | Perennial or annual herbs. Heads of yellow flowers with whorl of bracts below. | Pyrrolizidine alkaloids, volatile oils, and nitrogen oxides (fresh or dry). Acute toxicosis not common. Listlessness, aimless walking, increased pulse, rapid respiration, weakness, colic, delayed death (days to months). In cattle, prolapsed rectum from persistent straining. In horses, nervous signs evident in later stages. | Effects are cumulative. Liver biopsy diagnostic in early stages. Liver function test of value for subclinical condition in cattle. No general treatment. See pyrrolizidine alkaloidosis. |
Sorghum halepense Johnson grass | Weed of open fields and waste places; southern US and scattered north to New York and Iowa | All grazing animals | Coarse grass with large rhizomes and white midvein on leaf. Topped by large, open panicle. | Hydrocyanic acid (drought, trampling, frost, second growth) and nitrate (heavy in vegetative parts). Acute course. Difficult breathing, bloat, staggering, seizures, death. Blood bright red (cyanide) or chocolate brown (nitrate). | Hay safe for cyanide (volatile), not safe for nitrate (analyze). See cyanide poisoning and nitrate and nitrite poisoning. |
Sorghum vulgare Sorghum, Sudan grass, Kafir, Durra, Milo, Broomcorn, Schrock, etc | Forage crops and escapes; throughout North America | All | Coarse grasses with terminal flower cluster. Some to 2.5 m tall. | Hydrocyanic acid (drought, trampling, frost, second growth) and nitrate (heavy in vegetative parts). Acute course. Difficult breathing, bloat, staggering, seizures, death. Blood bright red (cyanide) or chocolate brown (nitrate). | Hay safe for cyanide (volatile), not safe for nitrate (analyze). See cyanide poisoning and nitrate and nitrite poisoning. |
Taxus spp Yew | Most of North America; Japanese and English yew common ornamentals | All except deer | Evergreen perennial tree or shrub. Bark reddish brown then flaking in scales. Leaves linear, 1.5–2.5 cm long, 2-ranked on twig, upper surface dark green, lower yellow-green, midribs prominent. Flowers unisexual, inconspicuous. Fruit single stony seed. Bright scarlet color. | Toxic alkaloids in bark, leaves, seeds. Gaseous distress, diarrhea, vomiting, tremors, dyspnea, dilated pupils, respiratory difficulty, weakness, fatigue, collapse, coma, seizures, bradycardia, circulatory failure, death. Death may be rapid. | Poisoning usually results when branches and trimmings fed to production animals. |
Triglochin spp Arrowgrass | Salt marshes, wet alkaline soils, lake shores; dangerous all seasons, especially dry season; northern half of North America | Sheep, cattle | Grasslike, except leaves are thick. Heads of fruits globular on erect raceme. Flowers inconspicuous. | Hydrocyanic acid in leaves. Salivation, dyspnea, excitement followed by listlessness, incoordination, prostration, seizures followed by death from anoxia. | Often, animals found dead. See cyanide poisoning. |
Definitive diagnosis of suspect plant poisonings is difficult. It is important to be familiar with the poisonous plants growing in the specific area and the conditions under which production animals may be poisoned. A tentative diagnosis is possible if the following information is available:
local soil deficiencies or excesses (which may complicate plant toxicities or simply confuse as to cause of a syndrome)
syndromes associated with each of the poisonous plants in the area
time of year during which each plant is most likely to cause problems
detailed history of the patients over the last 6–8 months
change of management or environmental condition that may cause an animal to change its diet or grazing habits (in some cases, eg, locoism, this may be all that is required in addition to identification of the plant involved)
Identification of the plant is important, whatever its stage of growth, and is especially useful if it can be identified in the gastric contents of the poisoned animal. Chemical analysis of toxicants often is not useful. Metabolic profiles are useful for some toxicities, and in some, the necropsy lesions are distinctive.
