USDA Plants Poisonous to Livestock in the Western States

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United States Department of Plants Poisonous Agriculture

Agricultural to Livestock in the Research Service Western States Agriculture Information Bulletin Number 415

Revised April 2011

United States Department of Plants Poisonous Agriculture

Agricultural to Livestock in the Research Service Western States Agriculture Information Bulletin Number 415

Revised April 2011

Prepared by K.E. Panter, M.H. Ralphs, J.A. Pfister, D.R. Gardner, B.L. Stegelmeier, S.T. Lee, K.D. Welch, B.T. Green, T.Z. Davis, and D. Cook, U.S. Department of Agriculture, Agricultural Research Service, Poisonous Plant Research Laboratory, Logan, Utah. Abstract lupine, milkvetch, milkweed, nightshade, nitrate, oak, photosensitization, pingue, poison hemlock, poisonous plants, ponderosa pine, Panter, K.E., M.H. Ralphs, J.A. rayless goldenrod, rubberweed, Pfister, D.R. Gardner, B.L. Stegel- Russian knapweed, selenium, meier, S.T. Lee, K.D. Welch, B.T. snakeweed, sneezeweed, spring Green, T.Z. Davis, and D. Cook. parsley, St. Johnswort, sweet 2011. Plants Poisonous to Live- clover, tansy ragwort, veratrum, stock in the Western States. U.S. waterhemlock, yellow star thistle, Department of Agriculture, Agri- yew culture Bulletin No. 415. The Agricultural Research Service Poisonous plants are a major cause conducts research to develop and of economic loss to the livestock transfer solutions to agricultural industry. Each year these plants ad- problems of high national priority versely affect 3 to 5 percent of the and provides information access cattle, sheep, and horses that graze and dissemination to— western ranges. These losses result from death of livestock, abortions, • ensure high-quality, safe food photosensitization, decreased and other agricultural prod- production, emaciation, and birth ucts; defects. In addition to these losses • assess the nutritional needs of are those of increased management Americans; costs associated with such things • sustain a competitive agricul- as fencing, altered grazing pro- tural economy; grams, and loss of forage. This bul- • enhance the natural resource letin describes more than 30 of the base and the environment; and principal poisonous plants growing • provide economic opportuni- on western ranges and the signs of ties for rural citizens, commu- poisoning in livestock. Suggestions nities, and society as a whole. are included for the prevention of livestock poisoning by plants. Mention of trade names, com- mercial products, or companies Keywords: abortion, arrowgrass, in this publication is solely for birth defects, bitterweed, bracken the purpose of providing specific fern, chokecherry, copperweed, information and does not imply death camas, emaciation, false recommendation or endorsement hellebore, greasewood, groundsel, by the U.S. Department of Agricul- halogeton, hemp dogbane, horse- ture over others not recommended. brush, kochia, larkspur, locoweed,

ii Caution: Pesticides used improp- regulations. Also, because registra- erly can harm humans, domestic tions of pesticides are under con- animals, beneficial insects, desir- stant review by the U.S. Environ- able plants, and fish or other wild- mental Protection Agency, consult life. Follow the directions and heed your local county agriculture agent all precautions on labels. Store or State extension specialist to pesticides in original containers be sure the intended use is still under lock and key—out of the registered. reach of children and animals— and away from food and feed. Use only pesticides that bear the EPA registration number and carry Apply pesticides so that they do appropriate directions. not endanger humans, livestock, crops, beneficial insects, fish, and While supplies last, single copies wildlife. Do not apply pesticides of this publication can be obtained where there is danger of drift when at no cost from USDA-ARS-NPA- honey bees or other pollinating PPRL, 1150 East 1400 North, insects are visiting plants or in Logan, UT 84341. ways that may contaminate water Copies of this publication may or leave illegal residues. be purchased in various formats Avoid prolonged inhalation of (microfiche, photocopy, CD, print pesticide sprays or dusts; wear on demand) from the National protective clothing and equipment, Technical Information Service, if specified on the label. 5285 Port Royal Road, Springfield, VA 22161, (800) 553-6847, www. If your hands become contami- ntis.gov. nated with a pesticide, do not eat or drink until you have washed. In This publication in its entirety also case a pesticide is swallowed or is freely accessible on the Internet gets in the eyes, follow the first aid at http://www.ars.usda.gov/is/np/ treatment given on the label and indexpubs.html get prompt medical attention. If a All photographs in this volume pesticide is spilled on your skin or were taken by USDA employees clothing, remove clothing immedi- except “Spineless Horsebrush,” ately and wash skin thoroughly. page 43, U.S. National Park Ser- Note: Some States have restric- vice; and “Rayless Goldenrod,” tions on the use of certain pesti- page 77, Dr. Samantha Uhrig, cides. Check your State and local Desert Willow Veterinary Services, Carlsbad, NM.

iii The U.S. Department of Agricul- ture (USDA) prohibits discrimination in all its programs and ac- tivities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orienta- tion, genetic information, political beliefs, reprisal, or because all or part of an individual’s income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET Cen- ter at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue SW, Washington, DC, 20250-9410, or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer.

Revised April 2011 iv Acknowledgments

The authors dedicate this latest revision of Plants Poisonous to Livestock in the Western States to Lynn F. James, Research Leader of the ARS Poisonous Plant Research Laboratory (PPRL) from 1972 to 2007. Under his guidance, PPRL gained a national and international reputation in the field of poisonous plants. He was the guiding force behind the original publication of this bulletin in 1980, and in 2005 he began the process of updating and revising the work. Dr. James retired from ARS in 2008 after over 50 years of service. He is a collaborator with PPRL and continues to share his insight and experience with the current staff.

The authors acknowledge Terrie Wierenga, PPRL, for her editorial and photographic suggestions; the ARS Information Staff for their assistance; Wilbert Blackburn, Area Director, ARS Northern Plains Area; and Evert Byington, ARS National Program Leader. This publication was prepared under the direction of L.F. James and edited by T.L. Wierenga.

v Contents

Poisonous Plants and Livestock...... 1 Economic Impact of Poisonous Plants on Livestock...... 4 Precautions for Using Herbicides...... 5

Poisonous Plants of the Western States

Arrowgrass...... 8 Bitterweed...... 10 Bracken Fern (Western Bracken)...... 13 Chokecherry...... 16 Colorado Rubberweed (Pingue)...... 19 Copperweed...... 22 Death Camas...... 24 False Hellebore (Veratrum)...... 27 Greasewood...... 30 Groundsel (Threadleaf and Riddell) and Houndstongue...... 32 Halogeton...... 36 Hemp Dogbane...... 40 Horsebrush...... 42 Kochia...... 45 Larkspur...... 47 Locoweed...... 51 Lupines...... 54 Milkvetches...... 58 Milkweed...... 61 Nightshades...... 64 Nitrate-accumulating Plants...... 66 Oak...... 68 Poison Hemlock...... 71 Ponderosa Pine Needles...... 74

vi Rayless Goldenrod...... 76 Selenium-accumulating Plants...... 79 Snakeweed (Broom and Threadleaf)...... 82 Sneezeweed...... 85 Spring Parsley...... 87 St. Johnswort...... 90 Sweet Clover...... 93 Tansy Ragwort...... 95 Waterhemlock...... 98 Yellow Star Thistle and Russian Knapweed...... 101 Yew (Taxus)...... 103 Other Poisonous Plants...... 105 Noxious Weeds...... 107

vii

Poisonous Plants and There are no known treatments for Livestock animals poisoned by most poisonous plants. Where a treatment is Poisonous plants are a major cause available, affected animals are of economic loss to the livestock usually in remote places and can- industry. Each year these plants ad- not be reached until it is too late versely affect 3 to 5 percent of the to provide treatment. Furthermore, cattle, sheep, goats, and horses that the stress of handling poisoned graze western ranges. All too often animals may increase the probabil- the losses to individual livestock ity of death. If the animals recover operations are large enough to enough to be handled, treatment threaten the viability of that ranch. should consist primarily of symp- tomatic treatment except where a Livestock losses can be heavy if specific treatment is known. animals— Prevention of loss from poisonous • graze ranges infested with plants in general is a problem of poisonous plants when plants range and livestock management. are most toxic. Under normal conditions, some • are driven, trailed through, poisonous plants form an impor- or unloaded from trucks onto tant part of livestock diets without range or pasture areas infested negative effects on the animals. with poisonous plants. Animals Poisoning occurs only when these are less selective in their graz- animals are enticed by hunger or ing at these times of stress. other stress conditions to eat too • are not watered regularly. much too fast. • are allowed to become hungry. Such animals are more likely Many of the death losses of to eat lethal quantities of poi- livestock from grazing poison- sonous plants. ous plants are due to manage- • are grazed on rangelands early ment error. This includes failure in spring when there is no to examine a pasture or range other green vegetation except prior to use because the growth of poisonous plants. some of these plants varies from • are stressed, such as when year to year. Failure to know and they are trucked, penned, or understand plants in an area that handled (branding, vaccina- are toxic to livestock can lead to tion, etc.). catastrophic losses. • are not limited on how much Hundreds of plants are poisonous and how fast they consume the to livestock. Many are toxic at all plants.

1 times, whereas others are toxic • Develop a grazing plan to im- only under certain conditions. prove your range and prevent Livestock producers are urged to poisoning. These plans should become familiar with the plants take into account the poison- on their ranges and pastures that ous plants on the range, allow- are potentially dangerous to their ing animals to graze them at livestock. Help in identifying these the most appropriate time or to plants can usually be obtained avoid them. from the local county agricultural • Do not allow animals that have agent or by mailing a sample to been under stress or that are the USDA-ARS Poisonous Plant overly hungry to graze in areas Research Laboratory (PPRL) for infested with poisonous plants. identification. (See PPRL contact • Provide adequate water for information at the end of this sec- your livestock. tion.) Help with poisonous plant • Be especially careful when problems can also be obtained grazing newly acquired live- from local veterinarians. stock on your range. • Provide adequate salt and other Proper diagnosis of livestock poi- supplements as needed, but do soning is essential. However, under not put them in an area where range conditions, diagnosis can be poisonous plants are growing. difficult. • Control poisonous plants where feasible. Symptoms listed for each plant are • If your animals get sick, con- those most likely to be observed. sult your local veterinarian to Not all symptoms will be seen in ensure proper diagnosis and all toxicities and signs of poison- treatment. If a poisonous plant ing may vary greatly, depending is involved, identification of on dosage and the time taken to the plant by an experienced consume the dose. Also, individual botanist or poisonous plant animals respond differently to expert is essential for any cor- specific poisons. rective action. To protect your animals from • Many poisonous plants can poisoning, do the following: function as useful forage. Poi- soning occurs when conditions • Learn to identify the poisonous develop that allow, or cause, plants that grow on your range. the animal to eat too much too • Learn the conditions under fast. which these plants can be dan- • Plants such as poison hemlock, gerous to your livestock. water hemlock, arrowgrass,

2 kochia, hounds tongue, and lupine may be growing on land from which hay is harvested. This is especially true on native pastures. Care must be taken when feeding this hay.

For additional information on poisonous plants, contact—

USDA-ARS Poisonous Plant Research Laboratory 1150 East 1400 North Logan, Utah 84341 phone: 435-752-2941 http://www.ars.usda.gov/npa/ logan/pprl

3 Economic Impact of Indirect losses (management costs) Poisonous Plants on include the following: Livestock • Building and maintaining fences Direct losses (effects on animals) • Increased feed requirements include the following: • Increased medical treatments • Altered grazing programs • Deaths of livestock • Decreased forage availability • Abortions • Decreased land values • Birth defects • Opportunity costs • Weight loss (due to illness or • Lost time to management decreased feed intake) • Stress to management • Lengthened calving interval • Decreased fertility • Decreased immune response • Decreased function (due to damage to organs such as the nervous system, lungs, liver, etc.) • Loss of breeding stock (due to deaths, functional inefficiency, etc.)

4 Precautions for Using first with your county agricultural Herbicides agent or weed specialist. They can suggest the most suitable chemical Herbicide rates in this publica- for a specific problem and recom- tion refer to the acid equivalent mend an optimum time and rate of (ae) or active ingredient (ai) application. of the active compound in the Use only pesticides that bear the herbicide, except for metsulfuron EPA registration number and carry (Escort), which is a dry flowable appropriate directions. formulation (60 percent ai) and is expressed as ounces of product Herbicides are safe when stored, per acre. handled, mixed, and used in accordance with label instructions Caution: Pesticides used improp- and sound agricultural practices. erly can harm humans, domestic Most herbicides are low in toxic- animals, beneficial insects, de- ity; however, some are poisonous sirable plants, and fish or other to humans, domestic animals, fish, wildlife. Follow the directions and and wildlife. Most herbicides are heed all precautions on labels. toxic to broadleaf crops. Store pesticides in original containers under lock and key, out of Label all herbicide containers the reach of children and animals, clearly and appropriately. and away from food and feed. Keep herbicides away from chil- Note: Some States have restric- dren, livestock, and pets. Store tions on the use of certain pesti- containers in a secured place where cides. Check your state and local they are not available to children regulations. Also, because registra- or anyone not authorized to use tions of pesticides are under con- them. Store herbicides in closed, stant review by the U.S. Environ- well-labeled containers in a dry mental Protection Agency, consult place where they cannot contami- your local county agriculture agent nate food, feed, or water. or State extension specialist to be sure the intended use is still When handling herbicides, wear registered. clean, dry clothing. Launder clothing after each spraying operation Always read the label carefully be- before wearing again. Wear protec- fore using any herbicide. Remem- tive clothing and equipment if ber that some chemicals, such as specified on the label. picloram, may have restricted use. Before using any herbicide, check

5 Apply pesticides so that they do In case a pesticide is swallowed or not endanger humans, livestock, gets in the eyes, follow the first aid crops, beneficial insects, fish, and treatment given on the label and wildlife. Do not apply pesticides get prompt medical attention. If where there is danger of drift when a pesticide is spilled on your skin honey bees or other pollinating or clothing, remove contaminated insects are visiting plants or in clothing immediately and wash ways that may contaminate water skin thoroughly with soap and or leave illegal residues. Avoid water. spraying in windy conditions. To protect fish, wildlife, and Do not inhale herbicides and avoid livestock, do not clean spraying contact with spray mist and drift. equipment or dump excess spray Avoid repeated or prolonged con- material in or near lakes, streams, tact of herbicides with your skin. or ponds. Keep herbicides out of your eyes, nose, and mouth. Consult the label Empty herbicide containers may for treatment recommendations. be hazardous. Dispose of them in accordance with label instructions If your hands become contami- or recommendations of your State nated with a pesticide, do not eat extension weed science specialist. or drink until you have washed. Do not burn herbicide containers.

6 Poisonous Plants of the Western States

7 Arrowgrass large amounts of arrowgrass leaves or stalks in a short Distribution of Arrowgrass time. The leaves contain substances that produce the poison hydrogen cyanide on ingestion.

Arrowgrass (Triglochin maritima and T. palustris) that is growing with adequate moisture does not cause poisoning. When growth is stressed or stunted from lack of Signs and Lesions of Arrowgrass moisture or frost, plants quickly Poisoning become toxic. Regrowth foliage following harvest is also toxic. The • Distress toxin in arrowgrass is the same as • Dyspnea; rapid breathing and that in chokecherry. gasping • Cyanosis (blue coloring of Where and When Arrowgrass the lining of the mouth) Grows • Increased salivation Species of arrowgrass are widely • Muscular twitching, stagger- distributed in marshy areas and wet ing, and convulsions meadows throughout the United • Bloat may occur; rumen con- States. Arrowgrass grows on wet, tents may smell like almonds alkaline soils and may be found • Convulsions growing over large areas or small • Coma patches near springs. Arrowgrass • Death (animals consuming starts growing in early spring. It large amounts of the plant is often found growing in native may die in 1 to 60 minutes meadows that are cut for hay. Ar- and show only convulsions rowgrass cut for hay may be toxic. and death as signs of poisoning) How Arrowgrass Affects • Blood and tissues a bright Livestock cherry red (hyperoxygen- ation) The amount of arrowgrass required • Tracheal and pulmonary to poison sheep or cattle depends congestion on the amount of poison in the • Cattle and sheep may be plants and the rate at which the severely affected if they eat plants are eaten. There is enough hydrogen cyanide, also known as

8 hydrocyanic acid or prussic acid, found in ¼ to 3 lb of stunted arrowgrass to kill a 600-lb animal. The toxic dose must be eaten at one time to cause death because the poison is not cumulative. Death results from respiratory failure.

How to Reduce Losses

Keep animals off areas where the growth of arrowgrass has been retarded by drought or frost or regrowth following harvest.

The action of hydrocyanic acid is so rapid that it is usually too late Arrowgrass is a perennial that has fleshy, dark-green, half-rounded, to treat an affected animal after the grasslike leaves that grow from the signs of poisoning are recognized. base of the plant. Although clumps of leaves are only 6 to 18 inches tall, Some poisoned animals may be slender flower stalks may reach a height of 5 feet. Small, green flowers saved by immediate treatment with appear close together along the an intraperitoneal injection of a upper part of the stalk early in the season. Later, the flowers develop mixture of 20 ml of a 10-percent into golden-brown fruits. solution of sodium thiosulfate and 10 ml of a 10-percent solution of sodium nitrite. For animals in advanced stages of poisoning, give an intravenous injection of the sodium thiosulfate and sodium nitrite solution. Consult your local veterinarian regarding treatment.

Arrowgrass can be controlled by metsulfuron (0.5 oz product/acre) when applied during seed stalk elongation.

9 Bitterweed • Head may be elevated • Bloat Distribution of Bitterweed • Congestion of liver, lungs, and abomasum • Inflammation and hemorrhage of abomasum and duodenum and sometimes the rest of the gastrointestinal (GI) tract; arched back is indicative of abdominal pain • Affected animals may lag behind the herd • Lambs may move with a stiff gait Signs and Lesions of Bitterweed Poisoning Bitterweed (Hymenoxys odorata) • Loss of appetite and weight poisoning is a major problem of • Depression sheep in the Southwest; cattle are • Weakness and irregular gait occasionally poisoned. Bitterweed • Vomiting and coughing is a member of the sunflower fam- (lips and muzzle are usually ily and is closely related to Colo- stained green with vomitus) rado rubberweed (pingue) both • Wasting and eventual death in appearance and in its effects

Bitterweed is a yellow-flowered annual weed varying in height from a few inches to 2 feet. It is erect and branches from the base. It is a bitter-tasting plant found mainly in the semiarid rangelands of the Southwest.

10 on sheep. Pingue is a perennial, the sheep start grazing the plant. whereas bitterweed is an annual. The animal will recover if removed Bitterweed has an extremely bitter from access to the plant at the taste and is unpalatable to live- first signs of poisoning. Generally stock; thus it is generally a prob- speaking, about 1 percent of the lem only when there is a shortage animal’s body weight of consumed of other green forage. Toxicity plant can be lethal. increases with plant maturity. The toxin is a sesquiterpene lactone. Bitterweed is a powerful irritant to the digestive tract; thus, poisoned Where and When Bitterweed animals may lose their appetite, Grows the rumen may stop functioning, and animals may show signs of Though bitterweed occurs from pain. They lose weight rapidly and southern Kansas to Mexico and may lag behind the flock. Animals from central Texas to California, it may not die until some time after is a problem of magnitude princi- removal from the plant. Post-mor- pally in Texas. The critical time for tem examinations of animals show livestock is generally in winter and lung, heart, and kidney changes early spring when animals may and irritation of the GI tract. graze the plant because of a shortage of other green forage. Maxi- How to Reduce Losses mum plant growth occurs in spring and early summer, but seedlings There is no treatment for bitter- may be found at any time of the weed poisoning. Recent research year, depending on moisture and has shown that sheep fed an acti- temperature conditions. vated charcoal/protein supplement were less affected by bitterweed How Bitterweed Affects than unsupplemented sheep. Ani- Livestock mals not severely poisoned may be taken from infested pastures, As with many other poisonous and they may recover within a few plants, the tolerance of animals to days if given good feed and water. bitterweed depends on many fac- Ranchers with bitterweed-infested tors. Acute poisonings may result pastures should be especially in death if large amounts are eaten aware of what their sheep are rapidly. Under normal conditions, eating, particularly in winter and this will not occur. Chronic poison- spring months, and should observe ing is common, with sheep devel- the flock frequently for early signs oping a wasting disease. Under of poisoning. natural grazing conditions, signs of poisoning occur 2 to 4 weeks after

11 Bitterweed poisoning has been prevented by moderate stocking in a four-pasture deferred rotation grazing system or light continuous stocking with sheep, cattle, and goats.

Seasonal control can be obtained from 2,4-D (1 lb ae/acre), picloram (0.5 lb ai/acre), clopyralid (0.25 lb ai/acre), or metsulfuron (1.25 oz product/acre) applied from autumn to early spring before flowering when the plant is actively growing.

12 Bracken Fern (Western • Twitching muscles Bracken) • General body weakness • Weak, fast pulse Distribution of Bracken Fern • Inability to stand • Convulsions or spasms • Pericardial and epicardial hemorrhage

Bracken fern (Pteridium aquili- num var. pubescens) is poisonous to cattle, sheep, and horses; sheep, however, are more resistant. Bracken contains a thiaminase inhibitor that leads to the development of thiamine deficiency in Signs and Lesions of Bracken horses that can be remedied by Fern Poisoning giving thiamine. Research has In cattle and sheep: indicated that bracken fern is also • High fever carcinogenic. Milk from cows that • Loss of appetite graze bracken fern may be hazard- • Depression ous to humans. • Difficulty in breathing • Excessive salivation • Nasal and rectal bleeding; bloody urine and feces • Anemia, leukopenia, throm- bocytopenia, and hemorrhagic syndrome • Hemorrhages on mucous membranes • Aplastic bone marrow • Bladder tumors in cattle

In horses:

• Loss of weight and condition; Bracken fern has broad, emaciation triangular leaves, or fronds. • Progressive incoordination The plant reaches a height of 2 to 4 feet. It grows directly from • Marked depression stout, black, horizontal root • Crouching stance, back stalks. arched with legs apart

13 Livestock losses have been high The poison in bracken fern has a in the Pacific Coast States, as well cumulative effect. Livestock are as in the Eastern and Midwestern affected only after they have eaten States and some areas of the Inter- considerable amounts of bracken mountain West. fern for 2 to 4 weeks.

All portions of the fern—both Cattle are affected by a nor-sesqui- green and in harvested hay—are terpene glycoside called ptaquilo- poisonous to livestock. The toxin side, which causes bleeding and is ptaquiloside, a nor-sesquiterpene damage to the bone marrow. The glucoside. disease has a delayed onset: Cattle may graze the plant for several Where and When Bracken Fern weeks and then get sick and die. Grows Poisoned animals seldom recover. If consumed over time, ptaqui- Bracken fern is widely distributed loside can also cause cancer in in many places around the world. the urinary bladder and GI tract. Bracken fern grows on burned- These tumors often bleed, causing over areas, in woodlands and other red urine (enzootic hematuria or shaded places, and on hillsides, redwater disease). open pastures, and ranges in sandy or gravelly soils. Bracken fern poisoning in horses can occur when they are fed hay The plant starts growth in the early containing about 20 percent brack- spring and usually remains green en fern over a period of 30 days. until the leaves are killed by frost. Signs of poisoning include weight How Bracken Fern Affects loss, incoordination, and lethargy. Livestock Horses may stand with their legs apart as though bracing themselves Bracken fern produces different and may assume a crouching posi- signs of poisoning in cattle and tion with an arched back. Muscle sheep than it does in horses. Cattle tremors develop and the animal poisoning often occurs during late is unable to stand despite violent summer when other feed is scarce, attempts to do so. Death will occur or when animals are fed hay con- in several days to a week. taining bracken fern. The disease occurs after cows have consumed How to Reduce Losses large amounts of the plant and is Animals seldom eat bracken fern manifested in an acute, usually if sufficient forage is available, so fatal, form. The disease is more grazing should be delayed until ad- chronic in horses. equate forage is available. Young

14 shoots are the most toxic and are relatively palatable in early growth stages.

To eliminate livestock losses, do not overgraze pastures and ranges. Make sure sufficient forage is available at all times to animals in infested areas. If necessary, supplement forage near the end of the grazing period. Do not feed hay contaminated with bracken fern.

Poisoning can be treated with thiamine hydrochloride, saline cathartics, and possibly activated charcoal. Few cattle have recov- ered after signs of acute poisoning appear; however, horses in early stages of poisoning may be saved by intravenous injections of thiamine hydrochloride. The thiamine hydrochloride treatment should be given under the direction of your local veterinarian.

Bracken fern can be controlled. In areas where cultivation is practical, the plants can be destroyed by cultivating the soil for 2 to 3 years.

15 Chokecherry Western chokecherry (Prunus virginiana var. demissa) and black Distribution of Chokecherry chokecherry (P. virginiana var. melanocarpa) cause livestock poisoning when drought and overgrazing strip the pastures and ranges of grass and other forage. Animals become poisoned if they eat considerable quantities of the leaves in a short time. Wilting, frost, or other damage to the plant enhances toxicity.

Both sheep and cattle may be poi- Signs and Lesions of soned by chokecherry. Although Chokecherry Poisoning most losses occur when feed is scarce, losses are not uncommon • Death (animals consuming when sheep graze chokecherry large amounts of this plant in the spring. Cattle sometimes may die in 1 to 60 minutes are poisoned by eating leaves on and show only convulsions branches trimmed from cultivated and death as signs of poison- chokecherry trees. ing) • Distress, rapid breathing, and The toxic substance in choke- gasping cherry, hydrogen cyanide (hydro- • Cyanosis (blue coloring of cyanic acid), is found principally lining of the mouth and mu- in the leaves. Leaves become less cosal membranes) toxic as the growing season ad- • Salivation vances. • Excitement may occur • Muscular twitching, stagger- Chokecherry and arrowgrass cause ing, and convulsions the same type of poisoning because • Bloat may occur; rumen they both contain hydrocyanic contents may have odor of acid. Other plants with cyanogenic almonds potential include serviceberry, • Coma Sudan grass, Johnson grass, white • Blood and tissue are bright clover, birdsfoot trefoil, mountain cherry red mahogany, and reed canary grass. • Tracheal and pulmonary congestion

16 Where and When Chokecherry animal consumes a relatively large Grows amount over a short period of time. For chokecherry to be fatal, an Chokecherry grows in damp and animal must eat a toxic dose in a fertile soil. It is found in thickets relatively short period—30 min- on hillsides and canyon slopes. It utes to an hour. Hydrocyanic acid appears as a shrub or small tree inhibits cellular respiration in all among willows, poplars, and alders body organs and causes respiratory that grow along mountain streams. failure. Signs of poisoning come on rapidly, and death may follow Chokecherry begins growing early within a few minutes. in spring. Its growth is slow at high elevations.

Chokecherry trees (center) may reach a height of 20 feet. They are often found growing with other trees and bushes. The berries are not considered to be toxic. Chokecherry may grow as a shrub to about 6-8 feet in height. It is found in thickets, along hillsides, and on canyon slopes.

How Chokecherry Affects How to Reduce Losses Livestock Keep hungry or thirsty animals off Although the hydrocyanic acid areas where chokecherry is abun- content of chokecherry leaves dant. varies, ingestion of about 0.25 percent of an animal’s weight in The action of hydrocyanic acid is leaves can be fatal. Wilted leaves, so rapid that it is usually too late as well as fresh leaves, are poison- to treat an affected animal after the ous. Poisoning occurs when an signs are recognized.

17 Chokecherry is a perennial that bears masses of white flowers in long clusters in the spring. Small ripe cherries range in color from purple to black. Leaves are dark green and glossy.

Some poisoned animals may be saved by immediate treatment. For both cattle and sheep, use 20 cc of a 10-percent solution of sodium thiosulfate mixed with 10 cc of a 10-percent solution of sodium nitrite given intraperitoneally or intravenously. Do not let animals become overexcited while they are being treated. For advice about treatment, consult your local veterinarian.

Control of chokecherry is not practical on a large scale.

18 Colorado Rubberweed Colorado rubberweed (pingue; (Pingue) Hymenoxys richardsoni var. floribunda) may cause serious Distribution of Colorado losses principally in sheep herds in Rubberweed Colorado, Utah, and northern and western New Mexico. Poisoning is common in sheep, but occurs occasionally in cattle. The plant is poisonous to livestock throughout the growing season. Losses are heaviest when hungry animals are trailed through Colorado rubberweed or are placed on overgrazed Pingue ranges with heavy infestations of Bitter rubberweed Colorado rubberweed.

All aboveground parts of the plant Signs and Lesions of Colorado contain the poisonous substance, Rubberweed Poisoning a sesquiterpene lactone. Animals • Salivation grazing the plant may have a grad- • Nausea and vomiting (area ual buildup of the toxin to a level about mouth may be stained that is harmful or lethal, or they green from vomitus) may eat large amounts of Colorado • Loss of appetite, rumen stasis, rubberweed and be poisoned im- abdominal pain mediately. • Weakness and depression Where and When Colorado • Irregular gait and trembling; Rubberweed Grows gait will become stiff • Emaciation and death may Colorado rubberweed is a peren- occur if animals are allowed nial that grows in arid sites at to graze this plant too long; elevations of 6,000 to 8,000 feet. death may not occur for some It is found mostly on mountains time after poisoning and foothills and grows from • Congested liver, lungs, and early spring until the first frost. It GI tract readily increases and may replace • Liver pale and fatty more palatable forage plants when • Enlarged spleen ranges have been overgrazed. • Hyperemia and hemorrhage of upper GI tract

19 How Colorado Rubberweed Affects Livestock

Most poisoning occurs in spring or fall. The plant seems to act primarily as a depressant of the digestive tract. In most cases, the first sign of poisoning to be observed is a green froth around the mouth and nose. A 100-lb sheep may die if it eats ¼ to ½ lb of Colorado rubberweed daily for 1 to 2 weeks, or it may die from one large feeding.

How to Reduce Losses Colorado rubberweed may reach a height of about 1 foot. The stalk is thick and Animals seldom eat toxic amounts woody. Stem bases are covered with a woolly growth. Colorado rubberweed of Colorado rubberweed if desir- belongs to the sunflower family. able forage is available.

Heavy losses during trailing may be prevented by avoiding heavily infested areas. Keep hungry animals away from Colorado rubberweed ranges at all times. If sheep losses become excessive, it may be advisable to change from sheep to cattle on certain ranges.

When grazing sheep on rubberweed-infested ranges, they should There is no known treatment for be watched closely for signs of Colorado rubberweed poisoning. poisoning. The rubberweed should be observed for signs of being Colorado rubberweed causes a grazed. At the first sign of poi- wasting disease similar to that seen soning (stiffness or a green stain from bitterweed and sneezeweed around the mouth) or grazing, poisoning. Sheep are more likely the sheep should be moved to a to eat it than cattle, and are prob- rubberweed-free part of the range. ably more sensitive to it. Lambs poisoned on rubberweed perform poorly and it may not be economical to keep them.

20 If Colorado rubberweed invades a range, examine your range management program carefully. On a range that is overgrazed, the desir- able forage plants are gradually crowded out and Colorado rubberweed begins to spread.

To control Colorado rubberweed, spray plants in the budding stages or during active growth with 2,4-D ester at 2 lb ae/acre.

21 Copperweed sesquiterpene lactone. Toxicity reaches a peak when the plant ma- Distribution of Copperweed tures. Leaves and stems are equally toxic.

Where and When Copperweed Grows

Copperweed grows along stream- beds or gullies where moisture is plentiful and the soils are usually alkaline.

Copperweed starts growing early Signs and Lesions of in spring. Flowers appear during Copperweed Poisoning July and August. • Loss of appetite • Dullness • Weakness • Coma and death in 1 to several days after ingestion of a lethal dose • Small hemorrhages on serosal surfaces • Mild gastroenteritis

Cattle and sheep may be poisoned from grazing copperweed (Oxyte- nia acerosa). They usually graze Copperweed is a perennial that may reach this plant only when other feed is a height of 4 feet. A large number of stems scarce. Cattle are more likely to eat grow from the crown; each has many narrow leaves. Small, flowering heads turn orange the plant in the fall when they are to yellow when mature. being trailed from summer range. Sheep are occasionally poisoned in How Copperweed Affects fall and winter by eating dry leaves Livestock that have fallen to the ground. Most losses occur in cattle. Cattle are more susceptible to copperweed poisoning than sheep. Copperweed contains a toxin that Three lb of copperweed or an is dangerous at all times. The toxin amount equal to 0.5 percent of the is not known but is probably a animal’s weight may cause death.

22 Poisoned cattle die in 24 to 28 hours. Poisoned sheep may linger 1 to 3 weeks before dying.

How to Reduce Losses

Animals seldom eat a toxic amount of copperweed if other forage is available. To reduce losses, provide adequate forage at all times. Supplemental feeding is beneficial before animals are driven through heavily infested copperweed ranges.

There is no known treatment for copperweed poisoning.

23 Death Camas • Death within a few hours to a few days Distribution of Death Camas • Congestion of lungs and kidneys • Minimal necrosis of skeletal and cardiac muscle

Death camas (Zigadenus spp.) is the common name of several species of plants that are poisonous to livestock. The more toxic of these species are grassy death camas (Z. gramineus), meadow death Signs and Lesions of Death camas (Z. venenosus), foothill Camas Poisoning death camas (Z. paniculatus), and Nuttall’s death camas (Z. nuttallii). • Salivation and bloody They are found principally in the frothing western range States. • Nausea and vomiting • Muscular weakness and Death camas is one of the first staggering plants to begin growth in early • Pulse fast and weak spring. Without sufficient other • Prostration, labored breath- forage, death camas may be heav- ing, gasping ily grazed and will cause severe • Coma losses. Spring snow storms may • Death due to heart failure cover all forage except death

Foothill death camas growing on a grassy hillside, a typical habitat where its density often reaches levels that are hazardous to grazing animals.

24 Death camas is a perennial that produces grasslike leaves in groups of three from a deeply buried bulb. The plant may be 4 to 16 inches tall. Yellowish-white flowers grow in clusters atop the stalk. Left, meadow death camas; right, foothill death camas. camas, which may protrude Where and When Death Camas through the snow and is available Grows to the livestock. Sheep are most likely to be affected by feeding on Some species of death camas death camas. Occasionally, cattle thrive on sandy soils; others grow and horses are poisoned. on drier, rocky foothills. The more toxic species are seldom found Death camas contains toxic steroi- above elevations of 8,000 feet. dal alkaloids that occur throughout Death camas grows early in spring, the plant; plants are dangerous at matures, and enters dormancy all times. during early summer when soil moisture declines. The bulb may be mistaken for those of the edible camas or qua- The leaves appear very early in mash (Cammassia spp.) and can the spring. In the foothills, death cause severe illness in humans. If camas generally flowers in April bulbs are eaten, take the affected and May. At higher elevations, the person to the emergency room of plant may flower in late June and the nearest hospital immediately. July.

25 How Death Camas Affects How to Reduce Losses Livestock To avoid poisoning, delay turn- Death camas causes marked dis- out until adequate good forage is turbance in respiration and heart available. Do not introduce hungry action. A 100-lb sheep may die if it sheep into heavy stands of death eats ½ to 2 lb of green foliage. The camas. Avoid feeding, bedding, or amount of foliage that will cause trailing sheep through heavy stands an animal’s death depends on the of death camas. species of plant eaten and the rate of consumption. Severely poisoned There is no known treatment for animals usually die; those less seri- death camas poisoning. ously affected may recover. Research results show that early in the season, when plants have three to six leaves, death camas can be controlled by spraying with 2,4-D at the rate of 1½ to 3 lb ae/acre. After the flowering stalks appear, spraying is not effective.

26 False Hellebore Sheep and goats readily eat the (Veratrum) whole plant. Cattle may eat it if other forage is scarce. Distribution of False Hellebore False hellebore is poisonous from the time it starts to grow until after it is killed by freezing, but toxicity decreases as plants mature. Roots are 5 to 10 times as poisonous as leaves or stems. The toxins in false hellebore are cyclopamine and other steroidal alkaloids.

Where and When False Hellebore Grows Signs of False Hellebore Poisoning False hellebore grows on moist, open meadows and hillsides at • Excessive salivation with elevations of 6,000 to 11,000 feet. frothing It emerges as soon as snow melts • General body weakness; in the spring. Flowers appear in animal may be unable to July and August, and the plant stand produces seeds in late August and • Irregular gait September. • Vomiting • Fast, irregular heartbeat How False Hellebore Affects • Slow, shallow breathing Livestock • Coma False hellebore poisoning may • Convulsions occur 2 to 3 hours after an animal • Birth defects eats the plant. Sheep may show False hellebore (Veratrum califor- slight or marked signs of poisoning nicum), or veratrum (sometimes after eating 6 to 12 ounces of green called wild corn and cow cabbage), stems or leaves. is a range plant that causes severe If pregnant ewes eat false hellebore poisoning in sheep. It also affects on the 14th day after breeding, the cattle and goats. If ewes, nanny young may have congenital defor- goats, and cows eat it during early mities of the head. These offspring, pregnancy, false hellebore causes a commonly called monkey-faced cyclopian-type (single eye) facial lambs, may have a protruding deformity in the offspring.

27 Leaves of false hellebore may measure 9 to 12 inches long and 3 to 6 inches broad. Cream-colored flowers grow in clusters at the top of a single unbranched stalk in a way that resembles corn. Seed pods turn black as they ripen. lower jaw, underdeveloped upper will eventually kill the ewe unless jaw, proboscis-like nose, cyclopia, the lamb is removed by caesarian. hydrocephaly, and a variety of Gestation has extended as long as deformities of the eyes as well as 240 days with the lamb weighing related deformities. There is a high over 30 lb when removed from the incidence of embryonic loss if the ewe (normal birth weight is 8 to plant is ingested between the 15th 9 lb). and 19th day of gestation. When ewes eat the plant later in gestation How to Reduce Losses (28th to 33th days), they give birth Losses of newborn animals from to lambs having tracheal stenosis deformities can be avoided by or shortened limbs. keeping sheep, goats, and cattle Ewes carrying deformed fetuses away from false hellebore during fail to lamb at the end of the nor- early gestation. Ideally, a flock mal gestation period. As the ewe of sheep should not be grazed on approaches term, the udder will veratrum for 60 days after the rams start to fill with milk and the ex- are turned in with the ewes. ternal genitalia will swell. At term, Research results show that false all indications of parturition will hellebore may be controlled by disappear and the fetus continues applying amine salts of 2,4-D at to grow to an abnormal size and

28 Typical cyclopic lamb, caused when the pregnant ewe grazed false hellebore on the 14th day of gestation. the rate of 2 lb ae/acre after the last leaves have expanded and before bud stage. A second treatment may be required the following year. Pi- cloram pellets at 1 lb ae/acre may also provide long-term control.

29 Greasewood Losses may occur when sheep or cattle eat large quantities of leaves Distribution of Greasewood that have fallen to the ground in fall and winter or new growth in spring.

The toxic substances, soluble sodium and potassium oxalates (also found in halogeton), accumulate in the leaves of the plant. The amount of toxin varies con- siderably among the different areas where it grows. Greasewood Signs and Lesions of Greasewood increases in toxicity as the growing Poisoning season advances.

• Depression Where and When Greasewood • Dullness, weakness, reluc- Grows tance to move This shrub is adapted to the heavy • Breathing rapid and shallow saline soils of arid and semiarid • Drooling regions. It is confined to alkaline • Recumbency soils and may form the dominant • Coma vegetation on alkaline flats. • Death between 2 hours and several days Greasewood starts growing in • Uremia, hypocalcemia, death early spring. The leaves remain due to interference with succulent until fall, when they energy metabolism dry and drop off. Buds remain on • Renal tubular necrosis with plants most of the year. crystals • Crystalluria How Greasewood Affects Livestock Greasewood (Sarcobatus ver- miculatus) is a range shrub that Signs of poisoning may develop livestock can safely eat in moder- 4 to 6 hours after an animal eats ate amounts with other forage. It is a toxic amount of greasewood. quite palatable to livestock. Death Greasewood poisoning in livestock occurs when livestock eat large is similar to that caused by amounts in a short period of time. halogeton. Poisoning occurs in sheep and cattle.

30 A sheep may die if it eats as little contains nontoxic levels of oxalate. as 2 lb of green leaves and fine Make sure animals are not hungry stems in a short period. Cattle when first allowed to graze grease- may die after eating 3 to 3 ½ lb of wood. Supply adequate water and greasewood in a short period. Most a good variety of forage. poisonings occur when hungry animals are turned into a patch of There is no known treatment for greasewood. greasewood poisoning.

How to Reduce Losses Research shows that greasewood can be effectively controlled with Rumen bacteria can metabolize the 2,4-D (2 lb ae/acre). Two or more toxin to a nontoxic form. There- successive years of treatment may fore, introduce livestock into heavy be necessary for effective control stands of greasewood slowly so because of its resprouting ability. as to allow time for them to adapt to the toxic substance in the plant (2 to 3 days). Livestock can also be conditioned to this toxin by grazing them on shadscale, which

Greasewood is an erect, spiny, woody perennial shrub that grows 2 to 5 feet tall. Flowers are small and light green to whitish.

31 Groundsel (Threadleaf • Death may occur within a few and Riddell) and days after symptoms appear • Icterus and hyperbilirubine- Houndstongue mia • Liver cirrhosis, fibrosis, and Distribution of Groundsels bile duct proliferation • Photosensitization

Threadleaf groundsel (Senecio longilobus), often called woolly groundsel, and Riddell groundsel (S. riddellii) contain pyrrolizidine alkaloids similar to those in tansy ragwort and thus may poison cattle, horses, and sheep. These groundsels occur in greatest abun- dance in the Southwest, notably in Signs and Lesions of Groundsel Texas, New Mexico, and Arizona. and Houndstongue Poisoning Riddell groundsel may also poison • Signs may not appear until livestock in the Midwest. Both 6 months or more after the plants have similar leaves that are plant is eaten thickish, elongated, and narrow. • Lethargy; loss of interest in Threadleaf groundsel leaves are food and abdominal pain gray, hence the name “woolly • Crustiness around eyes and groundsel,” whereas Riddell nose; eyes may also be red groundsel leaves are bright green. and watery, especially in Riddell groundsel has stems that bright sunlight are somewhat less woody than • There may be diarrhea or those of threadleaf groundsel, constipation which also tends to be more • Weakness as manifested by bush-like. wobbling and dragging rear feet Houndstongue (Cynoglossum • Animals may wander aim- officinale) is a biannual forb lessly and appear blind, and that infests pastures, ranges, and may become belligerent hayfields throughout the Western • Cattle may develop an un- United States. It is sometimes pleasant odor with a sweetish harvested in hay where it can cause quality poisoning. Houndstongue also con- • Ascites tains pyrrolizidine alkaloids (see

32 tansy ragwort). There are a number and goats are more resistant to of other plants that contain toxic poisoning than cattle and horses. amounts of pyrrolizidine alkaloids Younger animals are more suscep- such as Amsinckia and Crotalaria. tible than older animals. In some areas of the world, these plants grow mixed in with small Where and When Groundsels grains and subsequently end up and Houndstongue Grow in the food of people, with toxic Threadleaf groundsel typically consequences including carcinoge- grows in dry, gravelly, or hardpan nicity. There is some evidence that soils and may be found on plains pyrrolizidine alkaloids can pass and foothill areas; Riddell ground- through the placental membranes sel is generally found in slightly and have an effect on the fetus. moister sites, such as drainages and in sandy places. Houndstongue can be found growing in croplands and in the better soils.

Both groundsels flower in late summer, although in the Southwest threadleaf groundsel may grow and flower any time temperature and moisture conditions are right. Rid- dell groundsel usually dies back to the crown after flowering and fol- lows a more definite growth cycle.

How Groundsels and Houndstongue Affect Livestock

These groundsels and houndstongue contain pyrrolizidine alkaloids, which primarily affect the liver. Cells of the liver are Threadleaf groundsel, often called woolly groundsel because of its gray color, has slowly killed or prevented from many stems. Each stem may have several reproducing and are gradually branches. replaced by scar tissue. Whether an animal survives depends on the Toxicity increases up until time of number of liver cells it loses, and flowering; then it begins to de- the duration of survival depends crease. Younger plants tend to be upon the rate at which it loses liver more palatable to livestock. Sheep cells.

33 central nervous system effects such as impaired vision, belligerency, and an incessant stumbling walk.

The onset of symptoms may be de- pendent on other stresses imposed on the liver, such as cold weather, poor feed, shipping, or parturition, which it cannot handle in its weakened condition; thus, the true cause of death is often not ascertained.

Cattle eating 5 percent or more of their total daily diet of mature plant for periods exceeding 15 consecutive days can be expected to die within 1 to 6 months. A lesser amount of young plant may cause the same symptoms. Intoxications are often subchronic or chronic with clinical signs developing only after long periods of time. Such animals perform poorly throughout their lives and are culled because they are inefficient producers. Young animals are more easily poisoned than mature animals. Houndstongue is a biennial. The first year it produces a rosette with large rough leaves How to Reduce Losses resembling a dog’s tongue. The second year it produces a flowering stalk with When symptoms of poisoning reddish-purple flowers that produce four prickly nutlets. appear, it is too late to save the animal; thus, the best prevention is avoidance of the plant. Animals may survive for 6 months or longer after they have ingested Animals may graze pastures a lethal amount of plant and may containing these plants without ill show no outward symptoms during effects if an ample amount of good this period. They may suddenly be- forage is present; thus, pastures or come lethargic, fill with fluid in the ranges should be maintained for abdominal cavity, and die within good production of grasses and 2 to 4 days. They may also show high quality forage.

34 Riddell groundsel is a bright green plant which has several stems that originate from a woody base. Stems, if they branch, only branch terminally.

Groundsels may be controlled with Houndstongue can be controlled 2,4-D (1 lb ae/acre), picloram (1 lb with 2,4-D (2 lb ae/acre) or piclo- ae/acre), or a combination of 2,4-D ram and 2,4-D (0.25 to 0.5 lb ae/ and picloram (0.75 + 0.25 lb ae/ acre). Herbicide should be applied acre) when the plants are growing in spring prior to bloom. rapidly, but plants are generally spread over large areas and herbicide treatment may not be economically feasible.

35 Halogeton The toxic substance in halogeton is sodium oxalate. Halogeton Distribution of Halogeton becomes more toxic as the growing season advances, reaching a peak of toxicity at maturity. Cattle and sheep readily graze dried halogeton; thus, losses occur during fall, winter, and early spring. Losses generally occur when these livestock become hungry—during 1935-1957 trailing, after trucking, or over- 1958-1969 grazing.

Signs and Lesions of Halogeton Where and When Halogeton Poisoning Grows

• Depression, weakness, and Halogeton often grows along reluctance to move railroad beds, roads, sheep trails, • Respiration rapid and shallow and in places where the soil has • Drooling been disturbed. Dense stands are • Recumbency found on burned-over areas, over- • Coma grazed ranges, dry lakebeds, and • Death between 2 hours and abandoned dry farms. It thrives in several days; death due to the saline soils of colder arid and interference with energy semiarid regions of the Great Ba- metabolism sin, especially where native plant • Hypocalcemia, uremia cover is thin. However, halogeton • Renal tubular necrosis and lacks the capacity to compete with crystals, hemorrhage, and vigorous perennial plants and the hyperemia more aggressive annuals. • Rumen wall may be hemorrhagic and edematous Halogeton is a prolific seed producer. New plants germinate Halogeton (Halogeton glomera- from February to mid-August and tus), an alien invasive annual plant produce a seed crop before the of the Western States, frequently growing season ends. Seeds are causes poisoning in sheep and cat- spread by wind, water, animals, tle. Most losses occur when hungry and vehicles and equipment such animals are allowed to graze in as road graders. Seed may remain heavy stands of halogeton. alive in soil 20 years or longer.

36 Halogeton grows 3 to 18 inches tall; its height depends on the moisture available during the growing season. Each plant generally has five main stems that come directly from the base of the plant.

Halogeton has a characteristic small hair—about one-twelfth inch long—on the end of each leaf.

37 Halogeton forms a solid line along the roadside and extends into the sagebrush.

How Halogeton Affects Livestock are required to kill a sheep that has been feeding on other forage. First Toxicity is due primarily to sodium signs of halogeton poisoning occur oxalate, which can accumulate to 2 to 6 hours after an animal eats a high levels in the plant. Oxalates fatal amount; death usually occurs precipitate calcium from the blood in 9 to 11 hours. causing hypocalcemia; oxalate crystals damage the kidneys and How to Reduce Losses rumen walls, and enzymes are inhibited in the citric acid cycle of Livestock losses may be reduced energy metabolism, causing rapid by maintaining range in good con- death. dition and by proper management of animals. Supplemental feeding Sheep can tolerate large amounts helps prevent halogeton poison- of halogeton if they eat it slowly or ing when animals trail through or with other forage. The tolerance of graze infested areas. sheep doubles if they are precon- ditioned by grazing light stands or Do not introduce livestock into other plants containing low levels areas heavily infested with halo- of oxalates. geton unless it can be done slowly to allow time for adaptation to the About 12 ounces of halogeton will toxin. This can be accomplished kill a sheep that has been without by grazing plants such as shad- feed for a day or longer; 18 ounces scale or light stands of halogeton.

38 Livestock should not be allowed further (and potentially stronger) to become hungry or thirsty while invasion by halogeton (from seed grazing in areas infested with halo- in the soil) or other pioneer invad- geton as they graze indiscriminate- ers, such as Russian thistle and ly. Death in livestock occurs when rabbitbrush. an animal eats a large amount of halogeton in a short period of time. Caution: Use the herbicide only to Animals being trucked in should treat small infestations of haloge- not be unloaded in halogeton- ton. Repeated treatments are neces- infested areas. These animals may sary for control. benefit from supplemental feeding before grazing in the halogeton- infested areas. There is no known treatment for halogeton poisoning.

Halogeton does not compete well with other vegetation; therefore the best way to control halogeton is proper range management. Because each plant produces vast Some of the 1,200 sheep that died from numbers of seeds, some of which halogeton poisoning in a case from west central Utah. may survive for 20 years or more in soil, it is not practical to eradicate any population that has been in existence for 2 years or more. Plants can be held in control by proper use of herbicides, and very small infestations can be eradicated if treated early. Research results indicate that few herbicides are effective for halogeton control. The low volatile ester of 2,4-D (2 lb ae/ acre) is effective when applied in late May or early June. Applica- tions of 2 lb ai/acre of tebuthiuron as late as August will kill the halogeton and prevent reinvasion for 3 to 5 years. However, tebuthiuron is a sterilant and also kills the broadleaf forbs and shrubs, resulting in

39 Hemp Dogbane Normally, animals avoid hemp dogbane because of its bitter, Distribution of Hemp Dogbane sticky, milk-white juice. Sheep are more frequently affected than other animals; they will eat large quantities of hemp dogbane leaves and tops if other forb-type plants are not available. Hungry animals may eat hemp dogbane when they are turned onto harvested fields or onto new range in the fall or when other forage is scarce. Poisoning may also occur when sheep, cattle, and Signs and Lesions of Hemp horses are trailed from summer to Dogbane Poisoning winter ranges.

• Rapid pulse Leaves are poisonous at all times, • Dilation of pupils even when they are dry. The chief • Vomiting toxic substance in hemp dogbane is • Blue coloration of mucous thought to be cymarin, a glycoside membranes once used as a heart stimulant for • Progressive body weakness humans. • Convulsions may occur • Coma Where and When Hemp • Death Dogbane Grows • Mild myocardial degenera- Hemp dogbane grows on plains tion and foothills at elevations up to 7,000 feet. It commonly is found Hemp dogbane (Apocynum can- in gravelly or sandy fields, in nabinum), a poisonous plant found meadows, and along creekbeds, throughout the United States, may irrigation ditches, and fence lines cause occasional livestock losses in cultivated pastures. The plant in the western range States. The begins growing in late spring or plant gets its name from the fact early summer. that American Indians used fiber from the bark for making rope. How Hemp Dogbane Affects It also is called dogbane, Indian Livestock physic, American hemp, and rheu- matism weed. Death from hemp dogbane poisoning may occur 6 to 12 hours after

40 Hemp dogbane is a perennial that Leaves of hemp dogbane grow on opposite grows 2 to 5 feet tall. Leaves turn sides along reddish stems that contain yellow in the fall. a milky sap. The smooth-edged leaves are hairy on the lower surface. Flowers are greenish white. Two long pods, which develop from each flower, contain numerous seeds with tufts of silky white hairs at their ends. animals eat the plant. A lethal dose How to Reduce Losses for sheep is about ½ to 1 ounce per 100 lb of body weight. A lethal There is no known treatment for dose for cattle and horses is about hemp dogbane poisoning. ½ to ¾ ounce per 100 lb of body Research results show that hemp weight. A toxic dose depends dogbane may be controlled by largely on rate of consumption. repeated treatment of 2,4-D at 1 to Poisoned animals are usually 4 lb ae/acre. found dead; post-mortem pathol- ogy shows heart lesions.

41 Horsebrush Two species of horsebrush that grow in the Great Basin region of Distribution of Horsebrush the West are poisonous to sheep. Littleleaf horsebrush (Tetradymia glabrata) is commonly called coal-oil brush or spiny rabbitbrush. Spineless horsebrush (T. canescens var. inermis) is also called gray horsebrush.

Sheep that feed on horsebrush just Gray Horsebrush Little-leaf Horsebrush following or in conjunction with black sage (Artemesia nova) and Signs and Lesions of Horsebrush then are exposed to bright sunlight Poisoning may develop a characteristic swelling of the head (photosensitiza- • Loss of appetite tion) called bighead. Sheep graz- • Depression ing horsebrush may die without • Lagging behind the herd developing bighead; the liver is • Weakness, recumbency; death extremely friable. However, with may occur in severe cases, care, many of these sheep survive. or photosensitization may develop Most losses from horsebrush occur • Itching and uneasiness may during stormy periods when sheep develop with the head held in change their grazing habits as they a “looking up” position are trailed through heavily infested • Swelling of the ears, lips, and areas. Hungry sheep may also eat face toxic amounts of horsebrush after • Animal seeks shade they are watered. The plant is es- • Peeling of skin from face and pecially dangerous during the bud ears stage, perhaps because it is more • Abortion may occur palatable. • Liver is swollen, engorged, All plant parts of both species are and often shows severe fatty poisonous, but sheep eat only buds, changes leaves, and fine stems. • Kidneys show low grade nephritis • Petechial hemorrhages can be found in subcutis and serosal surfaces

42 Severe photosensitization (bighead) on sheep that grazed horsebrush. As little as one-half pound of littleleaf horsebrush can Spineless horsebrush is also called gray cause bighead. horsebrush. Photo courtesy U.S. National Park Service. day or two. Survivors, if pregnant, often abort and may require weeks Where and When Horsebrush to recover. Sheep eating lesser Grows amounts of the plant may become sensitive to sunlight and develop Littleleaf horsebrush is most various degrees of photosensitivity. abundant on benchlands, well- Severe photosensitization results in drained slopes, and low elevations bighead wherein the sheep’s head on sheep winter ranges. It is one is swollen. Sheep vary consider- of the earliest desert range plants ably in their susceptibility to horse- to start growing in spring; it may brush, but often ½ to ¾ lb of little- be green by late March and in full leaf horsebrush will cause bighead, flower by the end of June. Leaves and larger amounts may result in dry and drop off in early July, and death. Nearly twice that amount of the plant is dormant until the next spineless horsebrush must be eaten spring. to cause similar symptoms. Spineless horsebrush is most abun- Bighead develops only if the sheep dant in sagebrush areas and foothill has recently eaten black sagebrush. regions. It starts growing later than This plant enhances the action of littleleaf horsebrush and flowers horsebrush on sheep. in June or July. The plant usually remains green until fall. How to Reduce Losses

How Horsebrush Affects Bighead is principally a trail dis- Livestock ease. To prevent losses, select trail routes devoid of horsebrush and Horsebrush causes severe liver do not let animals graze in infested damage when large amounts are areas. Sheep are more apt to graze eaten, and sheep may die within a horsebrush during stormy periods.

43 Move affected sheep to shade as soon as signs of bighead appear. Give them water and supplemental hay. If possible, these sheep should be left undisturbed for a few days.

An effective economical method for the control of horsebrush has not been developed. Chemical and mechanical control in the area where littleleaf horsebrush grows is economically and physically impractical and ecologically un- sound. Littleleaf horsebrush grows in areas where it would be difficult and impractical to replace it with better forage. It is most practical to avoid horsebrush populations where possible.

44 Kochia variety of problems in cattle and sheep. Although not common, it Signs and Lesions of Kochia has been associated with oxalate Poisoning and nitrate poisoning. On occasion, it has been associated with photo- • Depression sensitization, polioencephalomala- • Dehydration cia, toxic nephrosis, and hepatitis. • Weight loss Diets having much kochia will • Muscular weakness result in decreased growth rates • Photosensitization and death can occur. The principal • Ocular discharge manifestation of kochia poisoning • Crusty muzzle is photosensitization. Poisoning • Blindness due to kochia apparently depends • Chronic nephrosis on the environmental conditions • Degenerative hepatopathy under which the plant is growing. • Elevated GOT (glutamic-ox- aloacetic transaminase), GGT Where and When Kochia Grows (gamma-glutamyl transpepti- dase), and serum bilirubin Kochia weeds can be found • Brain edema growing on abandoned farm land, • Fatty, cirrhotic, enlarged cultivated land, ditch banks, road livers sides, waste lands, and other • Gastrointestinal inflammation disturbed areas. It thrives in a • Icterus great variety of environments and • Ataxia soil types. Kochia is very drought • Incoordination tolerant. Kochia weed should not • Polioencephalomalacia be confused with prostrate kochia may occur (Kochia prostrata), which is considered excellent winter forage. Kochia (Kochia scoparia), or sum- How Kochia Affects Animals mer cypress, is an annual weed introduced into the United States Cattle and sheep may become from Eurasia. This plant can now intoxicated after grazing kochia. be found growing throughout the Cattle are more susceptible to United States as one of our seri- intoxication from kochia than are ous weed pests. Kochia has been sheep. Cattle grazing pastures with promoted in some areas of the a high percentage of kochia lose country as a forage plant. During weight or gain it slowly. Cattle drought years, it has been used grazing near pure stands of kochia both as forage and often as pastur- may show depression, dehydra- age. However, kochia can cause a tion, weight loss, photosensitiza-

45 Kochia is a bushy plant with stems either green or reddish. It is often confused with tumble- weed (Salsola kali) since it also breaks off and blows in the wind when dry. tion, and discharge from the eyes and nose. They may show signs of polioencephalomalacia. Death frequently occurs. The toxin may be any or all of the following compounds: oxalate, nitrate, sulfate, saponin, and alkaloid.

How to Reduce Losses

Ensure that alternative feed is available. During periods of drought, livestock producers frequently ask if it is safe to feed kochia to their cattle. In general, the advice given is to dilute the kochia with other hay if at all possible and watch the cattle closely for signs of poisoning. Grazing cattle on this plant leads to unpredictable results.

46 Larkspur

Distribution of Larkspur

Signs and Lesions of Larkspur begin flowering; consumption Poisoning increases into the pod stage. Sum- mer storms may lead to increased • Nervousness consumption of tall larkspur. • Weakness and staggering gait; animal may fall suddenly Losses rarely occur in sheep or • Salivation horses, but if subjected to sudden • Muscular twitching physical activity after ingesting • Nausea and vomiting may large amounts of larkspur, these occur animals may show clinical effects. • Bloating may occur • Rapid, irregular pulse Plants are most toxic during early • Animal may die suddenly; growth, but toxicity gradually excitement intensifies all declines over the growing season. signs of poisoning The toxic substances are alkaloids, • Lack of gross lesions and over 40 of these compounds • Pulmonary congestion have been evaluated. The rela- tive toxicity and concentration of Larkspur (Delphinium spp.) causes individual alkaloids varies among heavy cattle losses in western species. The toxic alkaloids cause range States. Larkspur is highly death by muscular paralysis, lead- palatable to cattle, and losses can ing to respiratory failure or bloat. be expected when cattle are allowed to graze larkspur-infested All parts of the plant are poison- ranges, especially where the plant ous, but new growth and the seed is abundant or grows in large, contain the highest concentrations dense patches. Cattle consume tall of toxic substances. Normally, larkspur most often after plants seeds do not pose any special prob-

47 nutallianum), and the plains larkspur (D. geyeri).

Tall larkspurs tend to grow at higher elevations on deep soils where a plentiful supply of moisture is available. They grow in mountain meadows on sites where deep snowdrifts persist well into the growing season, under aspens on north-facing slopes, along streams, or around seeps and springs. Tall larkspur begins growing as soon as snow melts, but at the upper limits of their distribution this may not occur until July.

Low larkspurs tend to grow at lower elevations where they ma- Tall larkspur is a perennial found on hillsides and in meadows above 7,000 feet. It ture and become dormant before ranges in height from 2 to 6 feet. A hollow the soil moisture is depleted. They stem distinguishes larkspur from poisonous monkshood, which has a similar blue or begin growing in early spring, purple flower without a spur. often before other forage begins growth. Low larkspurs grow best lem if cattle have grazed the area when springs are cold and wet. prior to seed maturity; however, Cattle will graze low larkspur at all under a rest-rotation system, where stages of growth, but most often cattle enter an ungrazed unit after graze it after flowering. seeds have started to mature, losses can be significant. Plains larkspur is found primarily on the high plains of Colorado Where and When Larkspur and Wyoming. It begins growth in Grows spring before other plants.

Based on height at maturity and How Larkspur Affects Animals geographic location, larkspurs have arbitrarily been divided into Plains larkspur may be eaten by three groups: the tall larkspurs (D. cattle at any time during summer, barbeyi, D. occidentale, and D. but early green growth and pods glaucum), the low larkspurs (D. may be most appealing to cattle. nelsonii, D. andersonii, and D. Both low and plains larkspurs may

48 How to Reduce Losses

Placing an affected animal on its brisket or chest with its head uphill may reduce bloating. Treatment for bloat (intubation or rumen punc- ture with a trocar) may save some animals. Avoid unduly exciting affected animals.

Toxicity of tall larkspurs declines as it matures through the growing season. Research has identified a toxic window of high risk during the flower and early pod stages when it becomes palatable and toxin levels are moderate.

Since cattle do not generally consume tall larkspurs before flowering, grazing early before plants flower may be an option. Cattle should be moved off of the larkspur areas during the flower stage Low larkspur has spurred blue flowers but can graze larkspur in the late that grow on the top third of a single, unbranched stem. It is found on grassy hill- pod stage when toxicity declines. sides and in sagebrush areas, where it may Using sheep to graze or trample reach a height of 2 feet. Leaves alternate tall larkspur patches ahead of cattle and are divided into deep, narrow lobes. The stem is hollow. grazing may reduce cattle losses. Low larkspur losses may be be the only green herbage available prevented by deferring grazing to cattle in early spring. until plants lose their flowers and The larkspurs contain a number pods, as they rapidly senesce after of alkaloids of varying toxicity. producing pods. The most toxic of these are the The cholinergic drug neostigmine MSAL (methyl succidimino acetyl (0.02 mg/kg i.m.) has been suc- lycoctonine) types, which include cessfully used under pen condi- methyllycaconitine. tions to reverse clinical larkspur intoxication. This reversal lasts about 2 hours, and repeated injec-

49 Toxic window theory of high risk for larkspur poisoning. When toxins are high, palatability is low; thus there is low risk of poisoning. Risk is highest when palatability is high and toxins are at moderate concentrations. tions of neostigmine are sometimes 4 lb ae/acre when the vegetative required. Under field conditions, development approaches its maxi- neostigmine temporarily abates mum but before the first flowers clinical signs and animals quickly open. (about 15 minutes) become ambu- latory. Depending on the larkspur Tall larkspur can be controlled dose, the intoxication can resur- with picloram (1 to 2 lb ae/acre) up face. Nonetheless, there are risks through the flowering stage. Met- associated with the use of neo- sulfuron (1 to 2 oz of product/acre) stigmine. The use of neostigmine- is effective when applied in the based treatments may actually early vegetative stage of growth. aggravate losses in the absence of Plains larkspur can be controlled further treatment because suddenly with picloram (0.25 to 0.5 lb ae/ mobile animals may later develop acre) in the bud stage. increased muscular fatigue and Do not graze cattle on larkspur dyspnea and may die. ranges treated with herbicide until Research results show that low larkspur is senescent in the fall. larkspurs can usually be controlled Herbicide treatment may increase by applying 2,4-D at the rate of palatability to cattle, but toxicity remains high.

50 Locoweed • Vacuolation of neurons, renal tubular epithelium, hepato- Distribution of Locoweed cytes, etc. • Recumbency and death may follow prolonged consumption of locoweed Horses, cattle, sheep, and goats are poisoned by eating locoweed. Wildlife such as elk and antelope

Oxytropis sericea belt also have been poisoned; loco- Astragalus lentiginosus belt weed is suspected in poisoning of Astragalus pubentissimus belt deer and bighorn sheep as well. Astragalus mollissimus belt The locoweeds belong to certain Signs and Lesions of Locoweed species of the Astragalus and Poisoning Oxytropis genera. Other species of Astragalus accumulate selenium or • Depression 3-nitro-propanol, which cause dif- • Dull, dry hair coat ferent types of intoxication. • Eyes dull and staring • Irregular gait or some loss of The plant gets its name from the muscular control Spanish word “loco” (crazy), • Weakness which describes the abnormal • Some animals show extreme behavior of poisoned animals. nervousness “Locoed” animals do not recover • Loss of sense of direction completely. Horses affected by • Withdrawal from other ani- locoweed have no value as saddle mals or draft animals. However, the fe- • Some animals develop males may be used as brood mares. inability to eat or drink • Abortions are common; hydrops may occur in some cattle • Skeletal malformations may occur • Animal may become violent if stressed • Reduced libido • Cessation of spermatogenesis and oogenesis Woolly loco is found from southwestern South Dakota south to Texas and New • Congestive heart failure when Mexico. grazed at high elevations

51 Generally, beef cattle poisoned on locoweed do not make economic gains, although they may appear to recover. Calf, lamb, and foal losses from abortion may be high. Skeletal birth defects are common; many lambs are lightweight at birth.

The more common species include white locoweed (Oxytropis sericea), woolly loco (Astragalus mollissimus var. mollissimus), spotted loco (A. lentiginosus), bigbend loco (A. mollissimus var. earlei), and garboncillo (A. wooto- nii). Loco is poisonous at all stages of growth. Plants are dangerous throughout the year—even when they have matured, dried, and Locoweed flowers resemble sweetpeas. Blossoms may be blue, purple, yellow, turned black. All plant parts are or white. Each stem contains numerous toxic. The toxin is the indolizidine leaves with a leaflet on its tip. Top, white alkaloid swainsonine, which is locoweed; bottom, spotted locoweed. produced by an endophyte (fungus growing within the plant). Absence Where and When Locoweed of the endophyte may result in Grows toxicity being greatly reduced or Locoweed is commonly found on absent in some plant populations. mountains, foothills, and plains and in semiarid desert regions. It starts growth in late fall, winter, or early spring—depending on local- ity, species, and moisture.

White locoweed grows from Montana, Idaho, and North Dakota south to Arizona, New Mexico,

Locoweed is found on foothills and semiarid and Texas. Spotted loco grows regions. It grows in tufts or clumps 4 to 24 from British Columbia, Canada, inches tall. to Mexico and east to Kansas and Oklahoma. Bigbend loco is native to the region of Texas for which

52 it was named; it also occurs in How to Reduce Losses southern New Mexico. Wooton loco (garboncillo) grows in eastern Locoweeds are relatively more pal- Arizona, southern New Mexico, atable than other forage at certain and southwestern Texas. Seeds seasons. Cattle prefer green-grow- may remain viable in the soil 50 ing locoweed to dormant forage on years or more. short-grass prairies in early spring, but will cease grazing locoweed Populations of all locoweed when it matures and warm-season species are cyclic. White loco is grasses begin rapid growth. On relatively long-lived but its popula- mountain summer range, cattle tions die out during major regional prefer the young succulent pods of droughts and gradually increase white locoweed. On desert winter during wet cycles. Woolly and range, cattle and sheep graze dry spotted loco are short-lived peren- senescent spotted locoweed (which nials, germinating during autumn retains the toxin) in proportion to or spring rains. They grow for 2 to its availability. Livestock should 3 years and then die from drought not be allowed to graze locoweed- or insect damage. Wooton loco is a infested sites when they are likely winter annual growing during wet to eat it. Once consumption of winters. locoweed stops, swainsonine is rapidly cleared from the body. How Locoweed Affects Livestock Livestock owners can reduce Signs of poisoning appear after losses by keeping animals off 2 to 3 weeks of continuous graz- locoweed-infested ranges until ing on the plant. Locoweed has good forage is available. four principal effects on livestock: neurological damage; emaciation; There is no effective treatment for reproductive alterations, such as locoweed poisoning. abortion and birth defects; and congestive right heart failure Locoweeds are particularly sus- when grazed at high elevations. ceptible to clopyralid (0.12 to 0.5 The toxin is excreted in the milk; lb ae/acre), picloram (0.25 to 0.5 calves nursed by cows poisoned lb ae/acre), metsulfuron (0.25 oz on locoweed have become intoxi- product/acre), and 2,4-D (2 to 3 cated. The neurological signs of lb ae/acre). All locoweeds have poisoning will disappear in time a large seed bank in the soil and but may recur when an animal will germinate and re-establish the poisoned on locoweed is moved population when environmental and stressed. conditions are favorable.

53 Lupines been poisoned by eating lupine plants that have been cut and dried Distribution of Lupine for hay.

Cows may give birth to calves with cleft palate and skeletal defects if the cows ingest certain lupines during early gestation (crooked calf syndrome).

Signs and Lesions of Lupine Poisoning

• Nervousness • Excessive salivation, frothing at the mouth • Depression • Reluctance to move about • Lethargy, inappetence • Difficulty in breathing • Twitching leg muscles Five poisonous species are silky • Loss of all muscular control lupine (Lupinus sericeus), tailcup • Convulsions lupine (L. caudatus), velvet lupine • Coma (L. leucophyllus), silvery lupine (L. • Death argenteus), and lunara lupine (L. • Cleft palate and skeletal formosus). Some lupine species are defects in fetus when grazed not poisonous to livestock, and not during 40th to the 100th day all species cause birth defects. of gestation Piperidine and quinolizidine alka- Sheep in the Western States are loids (ammodendrine and anagy- frequently poisoned by feeding on rine) are the compounds causing lupine. Poisoning usually occurs toxicosis and cleft palate as well as when hungry animals are allowed skeletal defects. to graze lupine. Losses may be es- Poisonous species of lupine are pecially heavy when hungry sheep toxic from the time they start are trailed through lupine ranges in growth in spring until they dry up late summer. Sheep and cattle have in fall. Younger plants are more

54 toxic than older plants; however, How Lupines Affect Livestock plants in the seed stage in late summer are especially toxic because The amount of lupine that will kill of the high alkaloid content of the an animal varies with species and seeds. Under proper conditions, stage of plant growth. It is not safe some lupines make good forage. to let sheep graze species such as L. argenteus under any condition. Where and When Lupines Grow Cattle may be poisoned by eating Lupines grow on foothills and 1 to 12 lb of lupine without other mountain ranges in sagebrush and forage. Smaller amounts are poi- aspen areas. sonous if cattle eat lupine daily for 3 to 7 days. Hay containing lupines Silky lupine grows in northern has caused poisoning and death areas from Washington and Oregon of cattle. Crooked legs and other east to South Dakota. Tailcup congenital deformities occur in lupine is found in Oregon, Cali- newborn calves if cows graze cer- fornia, Idaho, Utah, Montana, and tain species of lupine (L. sericeus, Wyoming. Velvet lupine is found L. caudatus, and L. laxiflorus) in an intermountain region from between the 40th and 100th days Oregon to Wyoming. Silvery of gestation. lupine occurs from North Dakota and Idaho south to Arizona and New Mexico. Lunara lupine grows in California.

Closeup shows typical circular pattern of lupine leaves.

55 Lupine is found on open and wooded hillsides. Poisonous species grow 1 to 3 feet tall. Leaves are composed of several Cleft palate of calf whose dam grazed leaflets, which radiate from a central point. teratogenic lupine during the early part of Although blue is the most common color, the susceptible gestational period. flowers may also be white, pink, yellow, or blue and white. How to Reduce Losses

Poisoning can be reduced by keeping hungry animals away from lupines in the early growth stage, in late summer when the plant is in the highly toxic seed stage, and from dense plant stands at all times. Supplemental feeding is beneficial, especially when animals are trailed through lupine ranges. If animals are poisoned on lupines, do not try to move them until they show signs of recovery.

If cows in the susceptible gestational period (40th to 100th days of gestation) are kept from lupine when it is most teratogenic (very

56 early growth or mature seed stage), most deformities can be prevented. The congenital deformity hazard is minimal at other gestation periods and after seeds have shattered from pods. The malformations can be avoided by adjusting the breeding season and the grazing of lupine- infested range to avoid the critical periods of gestation.

There is no known treatment for lupine poisoning.

Lupine can be controlled with 2,4- D (2 lb ae/acre), 2,4-D + dicamba (1 + 0.5 lb ae/acre), or triclopyr (0.5 to 1.5 lb ae/acre). Spray actively growing plants after they are 5 inches high but before they bloom. Reinvasion is rapid and re- treatment may be necessary every 4 to 5 years.

57 Milkvetches • Drooping of pelvic limbs and loss of control of hind limbs, Distribution of Milkvetches which may be dragged when animal moves • Indications of temporary blindness • Drooling; rough hair coat; constipation or diarrhea may occur • When forced to move rapidly, animal may collapse and die • All signs of poisoning increase with forced movement Signs and Lesions of Milkvetch • Lactating cows are more Poisoning commonly affected than non- lactating Acute Poisoning: • Animals with advanced • Respiratory distress poisoning seldom recover but • Muscular weakness primarily waste and die after several in pelvic limbs; prostration months • Death usually occurs in 3 to • Sheep show more respira- 4 hours tory and less neuromuscular • Lobular alveolar emphysema; involvement collapsed lungs and constrict- • Horses can be intoxicated; ed bronchioles with interlobu- cannot get them to back up lar edema • Focal hemorrhages in brain • Forced movement may cause • Wallerian degeneration in these animals to collapse spinal cord in pelvic region and die • Alveolar emphysema, inter- lobular edema Chronic Poisoning: • Death • Nervousness • Labored, rapid respiration Some milkvetches contain nitro • As intoxication progresses, compounds that are poisonous to respiration develops a wheez- cattle, sheep, and horses. These ing or roaring sound include plants such as Wasatch • Knuckling of fetlocks milkvetch (Astragalus miser • Goose stepping, knocking var. oblongifolius), Columbia of hocks and/or feet when milkvetch (var. serotinus), Yellow- walking stone milkvetch (var. hylophilus), red stemmed pea vine (A. emorya-

58 nus), and other species and variet- How Milkvetches Affect ies of Astragalus. Cattle and sheep Livestock of all ages are highly susceptible to the poisoning. Even when other The poison in milkvetches acts forage is available, cattle readily quickly. Two lb of green milkvetch eat some species of milkvetch. may cause acute poisoning or death in a 1,000-lb cow. Some Plants are poisonous from the time deaths occur within 1 hour, so fast they emerge but decrease in toxic- that cattle show no signs; more ity as they mature and dry up. often, animals die within 3 or 4 hours after eating the plant. Lactat- The poisonous substance in ing cows are more readily affected Wasatch, Yellowstone, and Colum- than dry cows. Do not stress cows bia milkvetches is the ß-D-gluco- that are grazing or have recently side of 3-nitro-l-propanol, or mise- grazed milkvetch. rotoxin. Other milkvetches contain glucosides of 3-nitropropionic Acute poisoning is characterized acid. Poisonous nitro compounds by a general muscular weakness are found in varying quantities in so that affected animals fall after 263 species and varieties of North the slightest excitement. The heart American Astragalus. beats very rapidly before the animal dies from heart failure. Where and When Milkvetches Grow Chronic intoxication may occur in cattle and sheep from graz- Milkvetches grow throughout ing any of the toxic varieties of much of North America. Poison- Astragalus miser, A. emoryanus, ous species grow on the meadows, and A. Canadensis—or other deserts, and forests in the Rocky nitro-containing Astragalus spe- Mountain States. Milkvetches cies over a period of several days emerge from late April to June, or weeks. Intoxication in cattle is depending on elevation and snow- characterized by goose stepping melt. Leaves and stems become (cracker heels), varying degrees of dry and are less dangerous after posterior paralysis, and respiratory seed dispersal in July or August. problems characterized by loud Red-stemmed pea vine (Astraga- breathing sounds (roaring disease). lus emoryanus) occurs in western This condition occurs in most of Texas and New Mexico. the Western States and Western Canada.

59 Flowers of Wasatch milkvetch resemble sweetpeas. They vary in color from creamy white to shades of violet.

How to Reduce Losses

To reduce losses, prevent animals from grazing these plants for extended periods. Feeding protein supplements has been shown to reduce intoxication. Avoid stressing cattle that have grazed these milkvetches. Cattle 3 years or older are less susceptible than younger ones. Cow poisoned on milkvetch. There is no known treatment for milkvetch poisoning.

Milkvetches can be controlled with 2,4-D (2 lb ae/acre), picloram, or clopyralid (0.25 lb ae/acre). Treat plants before they reach full bloom.

60 Milkweed

Distribution of Milkweed

Western whorled milkweed Mexican whorled milkweed Labriform milkweed Woolly pod milkweed Signs and Lesions of Milkweed Poisoning

• Depression, weakness, and staggered gait Milkweed is a perennial that often bears • Difficulty in breathing with blossoms and fruit at the same time. The expiratory “grunting” sounds plant may be 1 to 3 feet tall. Greenish-white • Dilation of pupils flowers are borne in umbrella-like clusters. Leaves may be narrow or broad. • Rapid, weak pulse • Loss of muscular control milkweed (A. fascicularis). The • Elevated temperature whorled, narrow-leaf milkweeds • Violent spasms are most toxic while the common • Bloating broad-leaf milkweed is relatively • Respiratory paralysis nontoxic. • Congestion of visceral organs • Renal tubular degradation and Milkweed poisoning occurs in necrosis chickens, turkeys, rabbits, horses, • Gastroenteritis cattle, sheep, and goats, with avian species being less susceptible than Several species of milkweed are mammals. Most livestock losses poisonous to livestock. Labriform are a result of hungry animals milkweed (Asclepias labriformis) being concentrated around heav- is the most toxic. Other species, in ily infested milkweed areas (such order of toxicity, include western as corrals, roadways, and bedding whorled milkweed (A. subverticil- grounds). However, poisoning lata), woollypod milkweed (A. may also occur when animals are eriocarpa), and Mexican whorled fed hay contaminated with milk-

61 Illustration of broadleaf (left) and narrow-leaf milkweed (right). Drawing courtesy of Holly Broome-Hyer, graphic artist, Logan, Utah. weed. The narrow-leaf, whorled Leaves and other aboveground milkweed species appear to be parts of the plant are the typical more palatable than the broadleaf cause of poisonings, but roots may species. Thus, poisoning incidents also contain toxic constituents. The from contaminated hay are more nonwhorled milkweeds contain a commonly associated with the variety of glycosidic substances whorled milkweeds. Similarly, called cardenolides that are highly field poisoning cases are more toxic. In contrast, the whorled common from the whorled milk- milkweeds generally contain very weeds. Milkweed may cause losses low cardenolide concentrations. at any time, but it is most danger- The whorled milkweed species are ous during the active growing thought to contain as yet uncharac- season. Livestock may be more apt terized neurotoxin(s). to graze these plants after a frost or when other available forage is limited.

62 Where and When Milkweed sheep and cattle and should not be Grows fed to them. When possible, rid the areas of milkweed and then man- Milkweed is often found in sandy age to prevent reinvasion. soils of plains and foothills. It grows on ranges and abandoned Milkweeds can be controlled with farms, along roadsides, in pastures, 2,4-D plus picloram (1 + 0.5 lb ae/ in ditches, and in waste places or acre) or glyphosate as a spot spray. overgrazed areas. This plant gets its name from the milky, sticky juice that oozes out quickly when any plant part is broken.

How Milkweed Affects Livestock

The toxicity of milkweed species is quite variable, ranging from relatively nontoxic to highly toxic. An average-size sheep that eats 1 to 3 oz of green leaves of one of the more toxic species is likely to die of poisoning within a few hours to 2 to 4 days. On a body weight basis, for the milkweeds that have been identified as being toxic, ingestion of as little as 0.05 percent to greater than 2 percent of an animal’s body weight can result in poisoning.

How to Reduce Losses

Animals usually do not eat milkweed unless good forage is scarce or when plants have been frosted.

Livestock owners can reduce losses by keeping animals out of milkweed-infested areas. Supple- mental feeding usually is beneficial during trailing. Hay contaminated with milkweed can be poisonous to

63 Nightshades The genus includes annual and (Solanum spp.) perennial herbs and shrubs that can be found throughout the United Distribution of Nightshades States. The principal species that serve as examples of the genus are black nightshade (Solanum nigrum), silverleaf nightshade (S. eleagnifo- lium), and buffalo burr (S. rostra- tum). Black nightshade is an introduced herbaceous annual weed that can be found growing mostly on disturbed soils and waste areas in the Eastern United States and into Signs and Lesions of Nightshade the Midwest. Silverleaf nightshade Poisoning is a perennial with long creeping rootstocks. Buffalo burr is an an- • Labored breathing and expi- nual native to the Great Plains and ratory grunt introduced to the West Coast. • Salivation and nasal discharge • Body temperature may be The toxins include a combination slightly elevated of a number of sugars and at least • Yellow discoloration of the six different steroidal amines com- skin may occur in chronic bined to form a variety of glycoal- poisoning kaloids. One example is the toxin • Apathy, drowsiness, progres- solanine. Potatoes are included sive weakness, paralysis, and with this group because the vines trembling and tubers that have been exposed • Increased heart rate to light can be toxic to livestock. • Fat may be yellowed and Drying does not destroy the toxin. gelatinous Nightshade species are not very • Gall bladder may be dis- palatable to livestock. However, tended these plants often grow as weeds • Gastrointestinal irritation in hay and silage crops and small including inflammation, hem- grains where they can be harvested orrhage, and ulceration with the crop and then fed to livestock. There are several species of nightshades that are toxic to horses, cattle, swine, sheep, and poultry.

64 Where and When Nightshades livestock except under the stress Grow of overgrazing or in contaminated hay and grain. Poisoning by this Black nightshade (both the native group of plants does not always and introduced varieties) is an an- end in death. In acute poisoning, nual 6 inches to 3 feet tall. Leaves the nervous symptoms develop are simple, ovate to lanceolate, en- rapidly. Death or recovery occurs tire to sinuate-dentate. Flowers are within a few hours to 1 or 2 days. white; berries are black when ripe. Death apparently is related to the It grows peripherally in moist areas paralysis. Chronic poisoning is of fields and pastures of disturbed accompanied by emaciation, rough loamy or gravelly soils throughout hair coat, anorexia, constipation, the United States. and ascites.

Silverleaf nightshade is a peren- How to Reduce Losses nial that grows 1 to 3 feet tall with white, hairy leaves and stems. Losses can be kept at a minimum Leaves are simple, thick, lanceo- by good pasture management and late to linear, entire to sinuate. weed control. Harvested for- Stems and ribs usually have short age such as hay, grain, or silage stiff spines. Flowers are violet or can be contaminated with night- blue; berries are yellow or orange. shades. Contaminated forage can Silverleaf nightshade grows in be fed if it is diluted (mixed) with fields, pastures, and roadsides from nightshade-free forage: an on/off Missouri to Texas and California. feeding strategy should be used. Animals being fed this diluted Buffalo burr is an annual spiny forage should be kept under close weed 1 to 2 feet tall. Leaves are surveillance and immediately re- irregularly round-lobed or once or moved from the contaminated feed twice pinnately deeply lobed; veins if signs of poisoning appear. are spiny. Flowers are yellow, and the berries are enclosed. Native to the Great Plains and introduced to the West Coast, buffalo burr grows in old fields, overgrazed pastures, and roadsides.

How Nightshades Affect Livestock

Nightshades are generally unpalatable and are not grazed by

65 Nitrate-accumulating fertilizers, machine oil, and some Plants natural well and pond waters. Plants differ in their ability to ac- Signs and Lesions of Poisoning cumulate nitrate. Often the type of by Nitrate-accumulating Plants soil present and the form of nitro- Acute poisoning: gen therein influences the amount • Blue coloration of mem- of nitrate that accumulator plants branes of mouth, eyes, and may contain. Drought conditions other mucous membranes or cloudy weather may enhance (cyanosis) nitrate accumulation. Treatment of • Shortness of breath nitrate-accumulating plants with • Staggering gait 2,4-D may also cause plants to ac- • Death cumulate excessive amounts of ni- • Chocolate-brown blood trate. Nitrate accumulates primar- • Muddy, cyanotic mucus ily in the vegetative tissue of plants membranes while the seed remains safe. • Congestion of rumen and Where and When Nitrate abomasum Poisoning Occurs

Subacute poisoning: Nitrate poisoning occurs through- • Watering eyes out the United States. Livestock • Unthrifty appearance may be poisoned after eating either • Reduced milk flow harvested or nonharvested plants, • Reduced weight gain feed materials high in nitrate, • Abortion and infertility nitrogen fertilizer, etc.

Many plants, both crops (oat hay, How Nitrate Poisoning Affects sorghum, corn, sudangrass, John- Livestock songrass, and beets) and weeds (carelessweed, kochia, pigweed, Nitrates are converted to nitrite in Russian thistle, and nightshade), ruminants. Nitrite causes the pro- can accumulate nitrate. Plants duction of methemoglobin, a form containing more than 1.5 percent of hemoglobin that cannot carry oxygen. Thus, the effects of nitrate nitrates (as KNO3) dry weight may be lethal to livestock. Sublethal poisoning result largely from oxy- effects may occur in livestock from gen starvation or suffocation. eating feed containing between The amount of plant material re- 0.5 percent and 1.5 percent nitrate. quired to poison an animal depends Nitrate poisoning can also occur on the amount of nitrate in the in animals that consume nitrate

66 plant and on the rate at which the plant is eaten. Many factors affect toxicity, but in general about 0.05 percent of an animal’s weight of nitrate is near a minimum lethal dose. Abortions in cattle have been associated with the consumption of high-nitrate forage or with ma- ternal poisoning resulting in fetal hypoxia.

How to Reduce Losses

Crops that accumulate nitrate and grow under conditions favoring nitrate accumulation should be checked for nitrate content. High- nitrate forage should be diluted with low-nitrate forage to decrease nitrate intake; or if there are indications of nitrate toxicity, the feeding of nitrate-accumulating forage should be discontinued. Adequate levels of readily fermentable carbohydrates (such as corn) can provide some protection against nitrate intoxication. Ruminants can adapt to relatively high dietary nitrate levels if the high-nitrate feed is increased gradually in the diet. Otherwise, mix a low-nitrate feed with the high-nitrate feed.

If the condition is identified soon after onset of clinical signs, animals poisoned on nitrate can be successfully treated by giving methylene blue intravenously at 2 to 4 mg/kg body weight.

67 Oak • Ascites and subcutaneous edema Distribution of Oak • Uremia; elevated BUN (blood urea nitrogen)

Cattle may be poisoned by brows- ing on oak in fairly large amounts over a period of 2 to 3 weeks. Shinnery oak (Quercus havardii) and Gambel oak (Q. gambelii) are the species responsible for most Gambel Oak Shinnery Oak losses. However, many other species can cause poisoning when a Signs and Lesions of Oak large amount of the oak plant ma- Poisoning terial is ingested. Shinnery oak, or shinnery, is common in the South- • Lack of appetite west. Gambel oak, also called • Gaunt, tucked-up appearance scrub oak, is found throughout the • Constipation, frequently fol- central part of the Western States. lowed by profuse diarrhea • Weakness Poisoning occurs primarily when • Rough, dry hair coat; dry animals graze buds and early muzzle growth leaves, sprouts in cut-over • Tendency to remain near areas, mature foliage, and acorns. water, excessive thirst Oak is most dangerous in the bud- • Reluctance to follow the herd ding and leafing stages and when • Emaciation acorns are available. As leaves • Mucus in feces mature, oak decreases in toxicity. • Frequent urination; dark-colored urine Cattle may get as much as 50 • Swelling under the jaw percent of their diet from oak • Subnormal temperature browse without showing signs of • Collapse poisoning. More than 50 percent of • Death oak browse in the diet will cause • Gastritis: abomasum and sickness, and more than 75 percent small intestine inflamed will cause death. Poisoning is most • Swollen kidneys likely during times of drought. • Nephritis with necrosis and The toxic substance in oak is prob- renal tubular casts ably a complex of tannins called gallotannins.

68 Where and When Oak Grows recover once oak consumption ceases. Milk production will de- Shinnery oak is a low spreading crease in lactating cows, and they shrub that grows in sandy areas. It will become emaciated. Goats are is found primarily in western Okla- less susceptible than cattle. homa, western Texas, and eastern New Mexico. How to Reduce Losses

Gambel oak is a shrub or small Livestock losses from oak poison- tree. It grows in dense thickets on ing can be reduced by conservative foothills and mountain slopes, up grazing and proper seasonal use of to an elevation of 9,000 feet. shinnery and Gambel oak ranges. Oak leaves decrease in toxicity as Oak usually starts growing in early they mature. spring before other range plants. In shinnery areas of the Southwest, How Oak Affects Livestock livestock owners should reserve pastures with the least amount of Death from oak poisoning may oak for early spring grazing. The occur from a few days to 2 weeks use of supplemental feed contain- after the cattle first show signs. ing 10 percent calcium hydroxide Chronic poisoning results in poor- will reduce losses. doing animals that never fully

Scrub oak may be a shrub 3 to 4 feet high or a tree up to 20 feet high.

69 In Gambel oak areas, animals should be kept off oak ranges until other forage becomes available and the oak leaves mature.

At first signs of poisoning, cattle should be moved to an oak-free area. In some cases, the use of a mild laxative, such as mineral oil, may be beneficial.

Oak can be controlled with tebuthiuron at 0.5 to 1 lb ai/acre applied to the soil in winter.

Caution: tebuthiuron is a sterilant and will kill all vegetation.

70 Poison Hemlock • Rapid, weak pulse • Respiratory paralysis Distribution of Poison Hemlock • Coma • Death • Convulsions have been reported • Occasionally bloody feces and gastrointestinal irritation • Skeletal birth defects and cleft palate in calves and piglets if cows or sows eat poison hemlock during susceptible stage of gestation: Signs and Lesions of Poison 40th to 100th days for cows, Hemlock Poisoning 30th to 60th days for sows

• Nervous trembling • Neuromuscular stimulation Poison hemlock (Conium macu- followed by depression and latum) can be found growing paralysis throughout the United States. • Ataxia, especially lower and Sheep, cattle, swine, horses, and hind limbs other domestic animals are poi- • Salivation soned by eating a small amount. • Lack of coordination It is also extremely poisonous to • Dilation of the pupils humans.

Poison hemlock has white flowers that grow in small erect clusters. Each flower develops into a green, deeply ridged fruit that contains several seeds. After maturity, the fruit turns grayish brown.

71 the plant flowers. Fresh leaves are unpalatable, so livestock seldom eat hemlock when other feed is available. The toxic compounds are coniine, γ-coniceine, and related piperidine alkaloids.

Where and When Poison Hemlock Grows

Because of its attractive flowers, poison hemlock was brought to the United States from Europe as a garden plant but has escaped cultivation and can be found growing in many pastures and in some areas on rangeland. Poison hem- Poison hemlock grows 4 to 10 feet tall. lock is found at roadsides, along Leaves are delicate, like parsley, and it fences and ditch banks, on edges has a white taproot. of cultivated fields, along creek- Poison hemlock is sometimes beds and irrigation ditches, and in confused with western waterhem- waste areas and may invade fields lock—a more deadly plant— or pastures. because the names are similar. (See Waterhemlock chapter in Poison hemlock is a biennial and this volume.) Poison hemlock belongs to the carrot family. It has a number of common names, starts growing in early spring but including deadly hemlock, poison does not flower until its second parsley, spotted hemlock, Euro- year. In favorable locations it may pean hemlock, and California or be a perennial. Poison hemlock Nebraska fern. harvested with hay can be toxic to livestock and produce birth Roots of poison hemlock may be defects. mistaken for wild parsnips and eaten by people. The stem of How Poison Hemlock Affects poison hemlock has purple spots Livestock on it. Poison hemlock ingestion is often All parts of poison hemlock— fatal. Sheep may be poisoned by leaves, stem, fruit, and root—are eating as little as 4 to 8 ounces of poisonous. Leaves are especially green leaves. Cattle that eat 10 to poisonous in spring up to the time 16 ounces may be affected. Signs

72 The hollow stem is marked with purple spots, a distinguishing feature. usually appear within an hour after Animals that recover seldom show an animal eats the plant. Animals lingering effects. die from respiratory paralysis in 2 to 3 hours. Convulsions, which are Research results show that poison common in waterhemlock poison- hemlock may be controlled by ing, seldom occur with poison treating plants before they begin to hemlock. bud with 2,4-D plus dicamba (2.5 lb + 1 lb ae/acre). Repeat applica- Skeletal deformities or cleft pal- tions may be needed. ate may be induced in offspring of cows, sheep, goats, and pigs if Hemlock Poisoning in Humans poison hemlock is ingested by the People may be poisoned by eating mother during susceptible stage any part of a hemlock plant. Often of gestation: 40th to 100th days poisoning occurs when the victim in cows and 30th to 60th days in has confused hemlock root with sheep, goats, and pigs. Palate and wild parsnips, hemlock leaves skeletal deformities in calves are with parsley, or hemlock seed with indistinguishable from the lupine- anise. induced crooked calf disease.

How to Reduce Losses

Avoid stressing poisoned animals that are not recumbent. For recumbent animals, support respiration and treat with activated charcoal and a saline cathartic. Gastric lavage may be beneficial, with atropine therapy to control para- sympathetic signs.

73 Ponderosa Pine Needles needles are generally grazed by cattle during cold winter weather Distribution of Ponderosa Pine when forage is lacking because of previous grazing or snow cover. However, cows may incidentally ingest dry fallen pine needles when grazing under tree cover. They may also eat needles from slash piles or windfall branches. The abortifacient compounds are diterpene acids including isocupressic acid and its metabolites.

Signs and Lesions of Ponderosa Pine Needle Poisoning

• Abortion characterized by weak parturition contractions, excessive uterine hemorrhage, and incomplete dilation of the cervix • Calves are weak but may survive if abortion is near term and extra care is provided Where and When Ponderosa • Persistently retained placenta Pine Grows • There may be indications of Ponderosa pine grows in all of the the impending abortion States west of the Great Plains and • Following the abortion, cows in Western Canada. Lodgepole may develop endometritis pine, some cedars, junipers, and and septicemia accompanied Monterey cypress can also cause by a marked increase in body abortions when consumed by temperature; cow may die if cows. treatment is not immediately provided How Ponderosa Pine Needles Affect Livestock The needles of ponderosa pine (Pinus ponderosa) cause abor- Abortions may begin within 48 tion when grazed by cattle. The hours after pine needles are in- abortions occur primarily from gested. Some cows abort as much late fall to early spring, during the as 2 weeks after having ingested last trimester of pregnancy. Pine the needles. Only a small amount

74 of needles is required to cause an abortion. Incidence can vary from only a few to 100 percent of the cows involved. There are no indications of overt toxicity to cattle eating the needles. If calves are far enough developed when the cow eats pine needles, they will be small and weak but may survive with proper care. Surviving calves may not nurse or may not be allowed to suckle by the dam; the dam may not have sufficient milk to feed the calf.

A persistently retained placenta is a constant finding regardless of the gestational stage of the abortion. Cows should be observed closely the first few days following an abortion. In case of complications from the retained placenta, consult a veterinarian. Some of these cows will die. The mortality of cows aborting from eating pine needles can be significantly higher than normal.

How to Prevent Poisoning

Prevent access to pine trees during the last trimester of pregnancy.

The ponderosa pine is a hardy tree extensively harvested for lumber. Both the dry and green needles and bark from the tree can cause abortion in cows.

75 Rayless Goldenrod • Myocardial necrosis and fibrosis of cardiac and skeletal Distribution of Rayless muscles in horses and goats Goldenrod • Degenerative changes of the liver

Rayless goldenrod (Isocoma wrightii or pluriflora), rosea, or jimmy weed, is an erect, bushy, unbranched perennial shrub, growing 2 to 4 feet tall. The leaves are alternate, linear, and sometimes sticky, and the flowers are yellow. It is toxic to horses, cattle, sheep, Signs and Lesions of Rayless and goats. The toxin, referred to as Goldenrod Poisoning tremetol (a mixture of compounds including tremetone, dehydro- • Lassitude and depression tremetone, 3-hydroxytremetone • Standing in a humped-up and 3-oxyangeloyl-tremetone), is position; stiff gait when walk- excreted in the milk of lactating ing animals, so the offspring of the • Trembling of muscles of nose animal or humans drinking the and legs, especially after milk may become poisoned by exercise; as the condition the consumption of contaminated worsens, the whole body may milk. The toxin is cumulative and shake is present in both green and dry • Weakness plant material. • Constipation and dribbling of urine Where and When Rayless • Recumbency Goldenrod Grows • Acetone odor on the breath • Coma This shrub grows on the dry range- • Terminal respiration consists lands from southern Colorado into of prolonged inspiration, a Texas, New Mexico, and Arizona. short pause, and forced expi- It grows especially well in river ration valleys and along drainage areas. • Death Poisoning is most common in late fall and winter.

76 How Rayless Goldenrod Affects How to Reduce Losses Livestock Poisoning of livestock by rayless Daily consumption of 1 to 1.5 goldenrod can best be prevented by percent of an animal’s weight of not overgrazing livestock on rang- the green plant for 1 to 3 weeks es infested with this plant and by will produce signs of poisoning feeding hay following snowstorms in horses, cattle, and sheep. Death that cover other forage. There is will result if the affected animals no treatment for poisoning by this are not removed from access to the plant but livestock may recover if plant. The condition it produces in they are not stressed and are given cattle is known as trembles. fresh feed and water; long-term effects are unknown.

Closeup of rayless goldenrod showing the leaves and flowers.

Rayless goldenrod in its natural environment. Photo courtesy of Dr. Samantha R. Uhrig, Desert Willow Veterinary Services, LLC, Carlsbad, NM.

77 Rayless goldenrod can be con- It affects all animals, including trolled by picloram or dicamba humans who consume milk from (1 to 2 lb ae/acre) in late summer affected animals (“milk sickness”). following adequate rainfall. It damages nearly all muscle types including the heart muscle, disrupt- White Snakeroot ing cardiac function. Death may result, especially when an animal White snakeroot (Eupatorium is stressed. White snakeroot grows rugosum) contains the same toxin in the Midwest and south into east- as rayless goldenrod (tremetol ern Texas and is most commonly compounds), and it is toxic to found in moist, shady, wooded cattle, horses, sheep, and goats. areas.

White snakeroot.

78 Selenium-accumulating Chronic Poisoning: Plants • Dullness • Rough hair coat Distribution of Selenium- • Emaciation accumulating Plants • Lack of vitality • Lameness • Hooves may become overgrown • Loss of long hair

Selenium is accumulated by a number of plants in sufficient amounts to be chronically toxic, and in some cases acutely toxic, if consumed by livestock. Plants Signs and Lesions of Selenium have been divided into three Poisoning groups, based on their selenium- accumulating ability. Acute Poisoning: • Abnormal posture Plants containing more than 5 ppm • Unsteady gait (parts per million) selenium are • Diarrhea potentially toxic. • Abdominal pain • Increased pulse and respiration rate • Prostration • Death • Petechial hemorrhage, en- docardia, acute congestion and hemorrhage of the lungs; enteritis and passive conges- Two-grooved milkvetch (Astragalus bisulca- tion of the liver tus) is a selenium-accumulating plant.

Sheep do not show the typical Primary selenium accumulator or signs of poisoning observed in indicator plants may accumulate cattle, horses, and pigs. Depres- up to several thousand parts per sion, increased respiration, and million selenium. This group sudden death are seen in sheep. includes species of milkvetch (Astragalus), woody aster (Mach- aeranthera section Xylorrhiza), goldenweed (Haplopappus section

79 Oonopsis), and princes plume The nonaccumulator group in- (Stanleya pinnata). Selenium cludes grasses such as western accumulated by these plants is wheat grass, small grains, and largely water soluble and in the alfalfa. Selenium absorbed by form of low-molecular-weight these plants is metabolized into organic compounds and selenate. plant proteins. These plants rarely The selenium is not incorporated accumulate more than 50 ppm into protein. selenium and usually only 5 to 12 ppm. On rare occasions, however, Secondary selenium accumula- several hundred parts per million tor plants may contain up to may be taken up. several hundred parts per million selenium, but lesser amounts are Where Selenium-Accumulating much more common. This group Plants Grow includes species of aster (Aster), milkvetch (Astragalus), saltbush The major seleniferous areas of the (Atriplex), Indian paintbrush West can be found in North and (Castilleja), toadflax (Comandra), South Dakota, Montana, Wyoming, gumweed (Grindelia), snakeweed Colorado, and Utah. Selenium (Gutierrezia), woody aster (Mach- poisoning occurs in the areas that aeranthera), and stickleaf (Mentze- have soils high in selenium. lia). In rare instances, these plants How Selenium Affects Livestock will accumulate up to several thousand parts per million. As in Selenium intoxication can occur the first group, selenium appears as acute (rapid death) or as chronic primarily as water-soluble selenate (hair loss, hoof lesions, etc.) poi- with smaller amounts of low- soning. Selenium is an essential molecular organic forms. nutrient. The problem in dealing with selenium is that the difference between the amount required for good nutrition and the amount that is toxic is very small.

The nonaccumulator plants are the most problematic of the selenium accumulators because they are commonly grazed by livestock. Aster sp., a secondary selenium Cattle and sheep grazing on these accumulator plants may have problems with overgrown hooves and reproduc- tion. Animals (both males and

80 females) may show few obvious signs of selenium poisoning but may suffer reproductive effects.

How to Reduce Losses

The only practical method of re- ducing losses in livestock to selenium poisoning is to prevent animals from eating excessive amounts of Princes plume (Stanleya pinnata), a primary selenium-containing plants. Soil selenium accumulator. and forage surveys or maps of the selenium content over a ranch or that are removed from seleniferous a range can be of great assistance forage may recover without appar- in developing a grazing or forage- ent permanent effects; however, production program. The amount recovery depends on the severity of selenium in soil and forage can of intoxication. vary markedly over an area.

Hooves of pigs fed selenium-accumulating plants. Note the cracks on the tops of the hooves. The chemical form of selenium in the soil can dramatically affect plant uptake. Identifying high-selenium and low-selenium areas, and when possible the form of selenium present, can help in deciding where to graze animals or if selenium supplementation is needed. Breeding horses or cows should not be pastured in a high- selenium area. Affected animals

81 Snakeweed (Broom and • Hematuria may occur Threadleaf) • Gastroenteritis • Hydropic degeneration and Distribution of Snakeweed necrosis of the liver; mild icterus • Toxic nephrosis • Uterine edema and possible hydrops of fetal membranes • Pregnant cows may have periodic vulvar swelling and earlier-than-normal udder development; they may abort and retained placenta is present. Signs and Lesions of Snakeweed Poisoning Broom snakeweed (Gutierrezia sa- rothrae) and threadleaf snakeweed • Listlessness (G. microcephala) are perennial • Periodic mucopurulent nasal weeds common on rangelands discharge with crusting and from Canada to Mexico. Cattle, sloughing of nasal mucosa sheep, and goats have been poi- • Anorexia and weight loss soned in large numbers from eating • Rough hair coat snakeweed; however, most losses • Diarrhea followed by occur in cattle. Snakeweed should constipation be considered for its toxic proper-

82 ties and for its abortifacient effects. broom snakeweed and only one Death may occur, but the principal or two for threadleaf snakeweed. effect of poisoning is abortion. Snakeweed grows on the drier Toxin levels increase through the range areas. Snakeweed is said growing season. Cattle will not to be more toxic when growing eat snakeweed unless other feed on sandy soils than on limestone is scarce. Abortions often follow soils (referred to as hard soils). In a snowstorm because snow covers the Southwest, it resumes growth the grasses leaving only the snake- following flowering in the fall and weed for the animals to graze. remains green over the winter. Far- ther north it begins growth in the spring and flowers in the late summer and early fall. Its populations are cyclic, increasing in wet years and dying back during drought.

How Snakeweed Affects Livestock

The amount of snakeweed needed to cause death or abortion in cattle varies greatly. Cows near term may abort or give birth to small, weak calves that may survive if properly cared for. Cows that abort have a persistently retained placenta. Cows aborting may develop endometritis and septicemia accompanied by an increase Snakeweed is a densely branched perennial in body temperature. These cows shrub that grows to 2 feet tall on dry range are at risk unless properly treated areas from Texas to California north to Colorado and Idaho and south into Mexico. by a veterinarian. Factors affect- ing dosage include site and stage Where and When Snakeweed of growth and rate of consump- Grows tion. The toxins are thought to be diterpene acids. Broom snakeweed and threadleaf snakeweed are very similar in ap- How to Reduce Losses pearance. They are distinguished Snakeweed increases with distur- by the number of ray flowers per bance (overgrazing, fire, drought). head: three or more ray flowers for Maintaining ranges in good condi-

83 tion can prevent dense concentrations of snakeweed. Snakeweed is not palatable. Adequate forage will prevent consumption of snakeweed. Cows in poor body condition probably eat more snakeweed than cows in better condition because the former graze less selectively.

Poisoned cows should be removed from snakeweed areas and given proper care until they recover.

In the Southwest, snakeweeds can be reliably controlled by spraying in the fall using picloram (0.25 to 0.5 lb ae/acre) or metsulfuron (0.5 g ai/acre). Further north in the Plains and Intermountain regions, these same herbicides and rates must be applied in early summer while snakeweeds are in the vegetative stage and growing rapidly.

84 Sneezeweed formerly Helenium) is common to many mountain ranges. Sheep Distribution of Sneezeweed are frequently poisoned by eating sneezeweed; cattle are rarely poisoned. Animals eat sneezeweed during summer and fall, when other forage is scarce or has become less palatable. Lambs poisoned on sneezeweed become unthrifty and are difficult to market. Poisoned ewes are often emaciated (wasting) and may not die until some time after removal from sneezeweed. Signs and Lesions of Sneezeweed Poisoning All plant parts are poisonous. The toxin is a sesquiterpene lactone. • Decreased appetite Sneezeweed, bitterweed, and rub- • Lips and muzzle become berweed have the same type of stained green from vomiting toxin. (spewing sickness) • Lambs become stiff and Where and When Sneezeweed wasted Grows • Depression Sneezeweed grows at elevations • Weakness with irregular pulse of 5,000 to 12,000 feet on moist • Frothing at the mouth slopes and well-drained meadows • Coughing from western Montana and eastern • Emaciation and wasting Oregon southward to California • Ascites and New Mexico. It starts growing • Gastrointestinal hyperemia in early spring and matures in late • Renal tubular necrosis summer and early fall. Sneeze- • Liver degeneration weed increases with overuse of the range. Heavy stands of sneezeweed Animals that feed on sneezeweed will inhibit growth of other plants. may become affected with “spewing sickness.” The disease gets its How Sneezeweed Affects name from its most characteristic Livestock sign—chronic vomiting or spewing. An animal may die if it eats small quantities of sneezeweed over a In the Western States, western long period. Sheep may be poi- sneezeweed (Hymenoxys hoopesii; soned by eating about 2 lb of green

85 sneezeweed leaves daily for 10 How to Reduce Losses days. Proper range management and Some animals die within a few improved range conditions will days after the first signs appear. reduce the risk of sneezeweed Others that develop a chronic form poisoning. Alternate grazing (on of poisoning may live for 2 to 3 and off) of sneezeweed areas at the weeks or more. Complete recovery proper times allows time for recov- from the poisoning is possible if ery. As soon as signs of poisoning animals are taken off the plants as appear, remove all animals from soon as the first signs are observed. sneezeweed-infested range for at least 14 days. Lambs usually show signs of stiffness before other symp- Practice open herding. Allow toms appear. Lambs left to graze animals free movement. Avoid sneezeweed after signs first appear grazing sheep continuously on become unthrifty (waste) and are sneezeweed-infested rangeland. unprofitable to keep. Ewes left on sneezeweed after signs appear will Sneezeweed can be controlled with waste and die. 2,4-D at 4 lb ae/acre.

Sneezeweed has one or several stems. Leaves are alternate, lance shaped, and smooth edged. Orange flowers with darker orange centers grow in clusters. Sneezeweed is a perennial of the sunflower family and is closely related to bitterweed and Colorado rubberweed.

86 Spring Parsley • Scabs form after blistering • Ewes and cows may refuse to Distribution of Spring Parsley allow young to nurse

Spring parsley (Cymopterus watsonii) causes a severe sunburn—or photosensitivity—in sheep and cattle. The plant also is known as cymopterus or wild carrot.

Animals do not die from eating spring parsley, but losses occur Signs of Spring Parsley when affected ewes or cows with Poisoning blistered, sore udders refuse to let their offspring nurse. Lamb losses • Sunburn of exposed areas are often high; calf losses usually • Reddening and blistering of are low. exposed areas of the body (nose, udder, external Spring parsley poisoning differs genitals) from bighead poisoning, a type of

Spring parsley is a perennial that grows 4 to 6 inches tall. It gets its name from the finely divided leaves that resemble parsley. Small white or cream-colored flowers are borne in umbrellalike clusters about one inch across. The plant has a long taproot. Spring parsley is a member of the carrot family.

87 photosensitivity caused by horse- Losses are primarily confined to brush, but is similar to St. John- lambs. On ranges where spring swort poisoning. The poisonous parsley is one of the first spring substances in spring parsley are plants to emerge, a ewe may eat two furocoumarins—xanthotoxin it soon after lambing. The udder and bergapten. and teats become so painful that the ewe will not allow the lamb Plants are poisonous from early to nurse. Newborn lambs may die spring until they mature and dry in of starvation or dehydration. The early summer. growth of surviving lambs is usually stunted from lack of milk. Where and When Spring Parsley Grows Cattle are affected if they are exposed to direct sunlight after eat- Spring parsley grows on well- ing about 1 lb of the green plant. drained soils, on rolling foothills, White areas on the body become and with sagebrush, piñon pines, “sunburned.” Cows refuse to let and junipers. It occurs at elevations calves nurse. In severe poisoning, of 4,000 to 8,000 feet. This is one all of the white areas of the body of the first plants to begin growing may blister, and animals may lose in early spring. It flowers from late weight rapidly. April to June and disappears by early summer. Sheep and cattle gradually recover after they stop eating How Spring Parsley Affects spring parsley. Livestock How to Reduce Losses Sheep and cattle are especially susceptible to spring parsley poison- To reduce losses, keep sheep and ing during March, April, and May. cattle off ranges infested with spring parsley in early spring until Sheep are affected if they are adequate forage is available. exposed to direct sunlight after eating as little as ¼ lb of the green There is no known treatment for plant. The photosensitization var- animals that are poisoned by spring ies from slight to severe; blisters parsley, but they will recover if form on areas of the sheep’s body kept in the shade and if skin le- not covered by wool. In advanced sions are treated. poisoning, all of the white areas of the body may be affected. Research results show that spring parsley can be controlled by

88 spraying plants in the bud to early bloom stages of growth with an amine salt of 2,4-D applied at the rate of 2 lb ae/acre.

89 St. Johnswort Young cattle and sheep are most often affected, but almost all Distribution of St. Johnswort white-skinned cattle, sheep, and horses react to eating the plant. Recently sheared sheep are especially susceptible. Although St. Johnswort seldom kills, it can cause severe economic losses.

St. Johnswort is toxic at all stages of growth. Young tender shoots may attract animals in spring. Nor- mally, cattle and sheep will not eat Signs and Lesions of mature St. Johnswort if they have St. Johnswort Poisoning other forage. Hay containing dry St. Johnswort can cause poisoning. • Restlessness • Scratching head with hind legs and rubbing head against solid objects • Crouching • Rapid pulse, increased temperature • Redness and swelling of white-skinned areas (sunburn) • Swollen eyelids, clouded eyes; possibly blindness • Peeling or sloughing of affected skin • Convulsions • Necrotic dermatitis

St. Johnswort (Hypericum perfora- tum), or Klamath weed, is a range plant that, when grazed by live- St. Johnswort is a perennial that grows stock, results in photosensitization. along roadsides and in meadows, pas- Animals that eat St. Johnswort and tures, rangelands, and waste places. In the Pacific Coast States, it may reach a then are exposed to direct sunlight height of 5 feet; in other areas, it grows 1 develop severe photosensitization to 3 feet tall. in white areas of the body.

90 Where and When St. Johnswort unpigmented areas are affected. Grows These areas itch and become red, swollen, and sore, and the skin St. Johnswort is an aggressive may peel or come off in large weed. It grows in old meadows, sheets (photosensitization). on pastures, along roadsides, on rangeland, and in waste areas. It White-skinned cattle are more usually is found growing on dry, susceptible to St. Johnswort poi- gravelly or sandy soils. It may soning than white-skinned sheep. grow in dense patches or mixed Cattle are poisoned by St. Johns- among other plants. It is con- wort if they eat an amount equal sidered a noxious weed in many to approximately 1 percent of their States. body weight and are then exposed to direct sunshine for 2 to 5 days. How St. Johnswort Affects In experimental feedings, sheep Livestock fed 5 percent of their body weight showed symptoms. When an animal eats St. Johns- wort, the poisonous compound in Signs of poisoning usually appear the plant, hypericin, sensitizes the 2 to 21 days after animals begin to skin to sunlight. Pigments in the graze St. Johnswort. skin shield colored skin from the sun’s rays so that only white or

St. Johnswort is a smooth-branched, erect plant. Leaves are covered with clear, small dots that contain the toxic substances. Five- petaled flowers grow in clusters; they are orange-yellow with occasional black dots along the edges.

Photosensitization due to eating St. Johnswort.

91 How to Reduce Losses

At the first signs of poisoning, move affected animals out of direct sunlight to shady or dark quarters. Treat affected skin areas as di- rected by your veterinarian. Give animals free access to fresh water and feed.

Research results show that St. Johnswort may be controlled by applying 2,4-D at 2 to 3 lb ae/acre. Biological control with the Klam- ath beetle is recommended for extensive infestations. For information about using the Klamath beetle, see your county agricultural agent.

92 Sweet Clover Where and When Sweet Clover Grows Distribution of Sweet Clover White sweet clover (Melilotus Sweet clover grows throughout the alba) and yellow sweet clover (M. Western United States. officinalis) are biennials that can be found growing along roadsides, Signs and Lesions of Sweet ditch banks, and often invading Clover Poisoning fields throughout the United States. These plants have been used • Signs occur 3 to 6 weeks after extensively as a forage crop and first exposure to spoiled plant soil builder. They are the cause of • Bleeding into muscles, joints, sweet clover poisoning, a severe or other tissues hemorrhagic disease of cattle. • Hematomas appear on neck, Only minor losses have occurred flanks, and hips in sheep. This bleeding condition • Excessive bleeding during is the result of the consumption of minor surgery moldy or spoiled sweet clover hay • Sudden death due to massive or silage by cattle. hemorrhage

Yellow sweet clover.

93 How Sweet Clover Affects Prevent poisoning by not feeding Livestock moldy clover to cattle, especially just prior to castration, dehorning, Sweet clover contains coumarin, or any surgical procedure. Cattle which is nontoxic but can be con- grazing sweet clover also bloat and verted to the dicoumarol by molds die. that grow on spoiled sweet clovers. The anticoagulant dicoumarol is an antagonist to Vitamin K. Dicouma- rol interferes with the synthesis in the liver of the vitamin-K-depen- dent clotting protein prothrombin. The likelihood of poisoning depends on the level of dicoumarol in the clover and the time over which the moldy clover is consumed by an animal.

The signs of poisoning usually occur 3 to 6 weeks after the start of feeding spoiled sweet clover. Sud- den death due to massive hemor- rhaging may occur. Bleeding may occur in muscles, joints, or other tissues. Hematomas usually occur in the neck, flanks, hips, and other body areas where the animal may be bumped, such as when eating in a stanchion or similar device. Excessive bleeding is associated with minor surgery.

How to Reduce Losses

Treatment consists of removing the moldy clover from the diet. A blood transfusion can be given to badly poisoned animals or vitamin K can be administered.

94 Tansy Ragwort within a few days after symptoms appear Distribution of Tansy Ragwort • Liver cirrhosis (necrosis and fibrosis) and bile duct proliferation • Ascites • Gastroenteritis

Signs and Lesions of Tansy Ragwort Poisoning

• Signs may not appear until 6 or more months after the plant is ingested • Lethargy and loss of interest in food

• Crustiness around eyes and Mature tansy ragwort may grow 4 or 5 nose; eyes may also be red feet tall. It has sturdy stems, has a strong and watery, especially in “weedy” odor, and produces great numbers of seed. Photo courtesy of Michael bright sunlight Shephard, USDA Forest Service. • There may be diarrhea or constipation Tansy ragwort (Senecio jaco- • Weakness as manifest by baea) is a weedy biennial plant wobbling and dragging rear that infests woodlands, pastures, feet and hayfields of the coastal north- • Animals may wander west United States. It is gener- aimlessly and appear to be ally unpalatable to livestock and, blind and may become therefore, is eaten only when other belligerent food is scarce or when it cannot be • Cattle may develop an avoided as a contaminant in hay, unpleasant odor that has a ensilage, and lush pastures. The somewhat sweetish quality toxins are pyrrolizidine alkaloids • The abdominal cavity may that are toxic to all classes of fill with fluid up to several livestock but most toxic to cattle gallons, and death may occur and horses. They cause a chronic,

95 cirrhosis-like condition of the liver, may survive for 6 months or longer which may lead to death of the after they have ingested a lethal animal several months after the amount of plant and may show tansy ragwort has been eaten. The no outward symptoms during this poisoning is thus difficult to diag- period. They may suddenly be- nose and death is often attributed come lethargic, fill with fluid in the to other causes. Death losses have abdominal cavity, and die within been reported from short-term 2 to 4 days. They may also show grazing of these plants. central nervous system effects such as impaired vision and continuous The rapid spread of the plant has walking with a stumbling gait. The been slowed due to the develop- onset of symptoms may be depen- ment of biological control proce- dent on other stresses imposed on dures. the animal, which it cannot handle in its weakened condition. Animals Where and When Tansy eating 5 percent or more of their Ragwort Grows total daily diet of prebloom tansy Tansy ragwort grows in areas with ragwort for periods exceeding 20 over 20 inches of rainfall annually; consecutive days can be expected however, it could possibly grow to die within 6 months. in heavily irrigated locations with How to Reduce Losses less rainfall. In the United States, tansy ragwort occurs principally The poisoning is irreversible and in coastal Washington, Oregon, the animal will die. The best way northern California, and in the to prevent tansy ragwort poisoning New England States. is to avoid the plant. Young animals are more easily poisoned than How Tansy Ragwort Affects mature animals. Pastures for horses Livestock and cattle with over 5 percent Tansy ragwort contains pyrroli- tansy ragwort should be avoided zidine alkaloids, which primarily until the tansy ragwort has been affect the liver. Cells of the liver controlled. Avoid hay and ensilage are slowly killed or prevented contaminated with tansy ragwort from reproducing and are gradu- because animals cannot sort out the ally replaced by connective tissue. tansy ragwort. Whether an animal survives Tansy ragwort can be controlled by depends on the number of liver cultivation. In other areas, research cells it loses, and the length of results show that tansy ragwort survival depends on the rate at can be controlled with 2,4-D (low which it loses liver cells. Animals

96 volatile ester or emulsifiable acid) at 1 to 3 lb ae/acre, dicamba at 0.5 to 1 lb ae/acre, picloram at 0.25 to 0.5 lb ae/acre, or metsulfuron at 1 to 1.5 oz product/acre. Spray tansy ragwort in the rosette stage. These herbicides will injure or kill legumes. Biological control methods have been developed; contact your extension agent.

97 Waterhemlock Waterhemlock may be confused with poison hemlock because of Distribution of Waterhemlock their similar flowers. However, these two are different plants and cause different types of poisoning. (See Poison Hemlock chapter in this volume.)

The underground portions of the plant, especially the tuberous roots, are very toxic. People are sometimes poisoned by eating the roots, which they mistake for wild Signs and Lesions of parsnip. Waterhemlock Poisoning

• Nervousness • Excessive salivation and frothing • Muscle twitching • Dilation of the pupils • Rapid pulse • Rapid breathing • Tremors • Violent convulsions, grand mal seizures • Coma • Death may occur as early as 15 minutes after a lethal dose is consumed • No significant gross lesions

Waterhemlock (Cicuta douglasii) Waterhemlock grows in wet seepage areas is the most violently toxic plant such as meadows, pastures, and along the that grows in North America. banks of streams. It reaches a height of Only a small amount of the toxic 2 to 4 feet. The plant is a perennial in the carrot family. substance in the plant is needed to produce poisoning in livestock or In cases of waterhemlock poison- in humans. The toxin, cicutoxin, ing in humans, take the affected acts on the central nervous system person to the emergency room of and is a violent convulsant. the nearest hospital immediately.

98 Call poison control and seek emergency treatment immediately.

Cattle have been known to eat lethal amounts of waterhemlock in pastures having adequate forage; therefore, animals should be prevented from grazing over waterhemlock-infested areas. Ani- mals have been poisoned by eating roots that have been brought to the surface by plowing or cleaning ditches.

The toxic substance in waterhemlock is cicutoxin, a highly poisonous unsaturated alcohol that has a Waterhemlock has small, white flowers that strong carrot-like odor. It is found grow in umbrella-like clusters. Side veins of principally in the tubers but is also the leaves lead to notches, not to tips at the outer margin. present in the leaves, stems, and immature seeds. Leaves and stems How to Reduce Losses lose most of their toxicity as they mature. The toxic substances act so rapidly that an affected animal can seldom Where and When Waterhemlock be saved. Treatment consists of Grows preventing seizures with barbitu- Waterhemlock is most commonly rates or tranquilizers and support- found growing in wet meadows ing respiration. Gastric lavage, and pastures and along stream activated charcoal, or saline cathar- banks. It starts growing in spring. tic may be helpful. Seek immediate Waterhemlock usually flowers in medical or veterinary treatment. June or July. To reduce losses, keep animals How Waterhemlock Affects away from places where water- Livestock hemlock grows. Prevent waterhemlock poisoning in livestock by Livestock usually show signs of carefully surveying pastures and poisoning 15 minutes to 6 hours ranges at a time when the plant can after eating the plant. They develop be identified, and eradicate it. violent convulsions and may die within 15 minutes to 2 hours after The plants, which usually grow in signs appear. small patches, are easy to locate.

99 The thick rootstalk of waterhemlock contains a number of small cham- bers. These hold a highly poisonous brown or straw-colored liquid that is released when the stem is broken or split. Thick, fleshy tubers and slender individual roots grow from the bottom of the rootstalk.

They can be eradicated by spray- plants for 3 weeks after spraying or grubbing. Actively growing. Most losses occur early in the ing plants can be controlled with spring or after the plants have been 2,4-D at 2 lb ae/acre. Repeat spray sprayed with 2,4-D. treatments until eradication is complete. The stems and leaves of Note: If grubbing the waterhem- waterhemlock increase in palat- lock, use gloves and be careful to ability immediately after being get all of the plant, including roots. sprayed with herbicide. Therefore, Gather and burn every part. keep animals away from treated

100 Yellow Star Thistle and How Yellow Star Thistle and Russian Knapweed Russian Knapweed Affect Livestock Distribution of Yellow Star Yellow star thistle and Russian Thistle and Russian Knapweed knapweed are toxic primarily to Both plants grow throughout the horses. They are grazed only after Western United States. other forage is gone.

Signs and Lesions of Poisoning It takes weeks to months of exposure to large amounts of yellow • Clinical signs occur after the star thistle or Russian knapweed horse has eaten large quanti- before clinical signs develop. ties of either plant for 30-60 Horses must consume 86 to 200 days percent of their weight in green • Chewing disease (dysfunction plant. of facial, mouth, and throat muscles) • Facial paralysis • Depression • Dehydration and malnutrition • Incoordination • Muscle tremors • Irreversible necrosis of the brain

How and When Yellow Star Thistle and Russian Knapweed Grow

Yellow star thistle (Centaurea solstitialis) is an annual weed growing throughout much of the Eastern, Southern, and Western United States. Russian knapweed (C. repens) is an invasive peren- Yellow star thistle is an annual weed that nial weed that spreads via seed and grows up to 12 inches tall. Leaves are covered with cottony hair, and the yellow rhizomes. It is abundant through- flowers are surrounded by the characteristic out the intermountain west and stiff yellow spines up to an inch long. the northern plains. They are both characterized as noxious plants.

101 Horses develop chewing disease; How to Reduce Losses signs of poisoning include twitching of lips, tongue flicking, invol- There is no effective treatment untary chewing motion, drowsi- for poisoning. The necrosis in the ness, weight loss, and emaciation. brain is irreversible. Eating and drinking are severely The best prevention is to control impaired. Prehension and mastica- the plant and keep pastures where tion are affected, but swallowing horses graze in good condition, is unaffected. The mouth is often provide adequate good quality held partly open with the tongue feed, and avoid overgrazing. partially protruding.

Most poisoning cases are in younger horses.

Russian knapweed is a perennial that grows 1 to 3 feet tall. The flowers are similar to some thistles and are lavender to white. There are no spines around the flowers.

102 Yew (Taxus) • Survival is rare • Moderate irritation of the Signs and Lesions of Yew upper digestive tract Poisoning Yews (Taxus spp.) are shrubs that • Gastric distress are used extensively in landscaping • Diarrhea around homes and other buildings. • Vomiting Yews have long, slender, alternate • Tremors dark-glossy-green flat needles and • Dyspnea bright-scarlet fleshy cup-shaped • Dilated pupils fruits. In some areas, the yew is • Respiratory difficulties considered the most toxic tree or • Weakness shrub and is probably one of the • Fatigue most toxic of all poisonous plants. • Collapse • Coma Yew is toxic to all classes of • Convulsions livestock, large game animals, and • Bradycardia humans. Poisonings usually occur • Circulatory failure when these plants are trimmed and • Death (may be so rapid that the trimmings are fed to animals. signs of poisoning may not Children are poisoned when they have time to develop) eat or chew on the scarlet fruit.

Closeup of leaves of Japanese yew (Taxus cuspidata). Japanese yew is commonly used in horticulture.

103 Foliage, bark, and seeds are all toxic. The foliage is readily eaten by livestock.

Where and When Yew Grows

There are about 40 species of Taxus that can be found growing throughout the United States. Four of these are commonly used in horticulture.

How Yew Affects Animals

Green foliage is toxic to horses and other monogastric animals at about 0.1 percent of body weight. In ruminants, about 0.5 percent of body weight of foliage is toxic. The toxin is an alkaloid, taxine. The compound is a cardiac depressant causing the heart to stop.

How to Reduce Losses

Do not allow animals access to this group of plants. Control is mostly a matter of horticulture and landscaping decisions to prevent grazing animals from access. The general public should be educated not to put clippings of those plants where animals have access.

104 Other Poisonous Plants Arizona. Poisoning occurs primarily in cattle. Signs of poisoning include loss of appetite, diarrhea, restlessness, arched back, depression, coma, and death. Drymary is exceedingly distasteful to livestock.

Horsetail (Equisetum spp.) is an herbaceous perennial. It is rush- Cocklebur. like in appearance with hollow, jointed stems. This group of plants Cocklebur (Xanthium strumarium) is common throughout the United is an annual plant that grows in States. It is toxic primarily to dry lakebeds, river bottoms, and horses and cattle. disturbed and flooded areas of fields, pastures, and roadways after water disappears. Poisoning occurs primarily in cattle, sheep, horses, and swine when the plant is eaten in the cotyledon stage (seedling). Signs of poisoning include rapid, weak pulse, labored breathing, nausea, vomiting, and spasmodic contractions of the legs and neck muscles.

Desert baileya (Baileya multira- diata) is a small annual that grows in dry, sandy and gravelly areas from Texas to southern California. Sheep are sometimes poisoned on this plant. Signs of poisoning include depression, anorexia, and slobbering of a green material from Horsetail. the mouth. Jimsonweed or thornapple (Datura Drymary or inkweed (Drymaria spp.) is a large annual herb with pachyphylla) is a short-lived an- worldwide distribution. It is toxic nual that grows close to the ground to all classes of livestock as well on alkaline clay soil in western as humans. Signs of poisoning Texas, southern New Mexico, and include dilated pupils, subnormal

105 temperature, restlessness, gastric Hundreds of plants are poisonous stasis, bloat, muscular twitching, to livestock. Many are toxic at all incoordination, paralysis, rapid times, whereas many others are heart rate, and respiratory toxic only under certain conditions. paralysis. Livestock producers are urged to become acquainted with the plants Tansy mustard (Descurainia pin- on their ranges and pastures that nata) is an annual weed that grows are potentially dangerous to their on dry, sandy soils in arid areas. livestock. Help in identifying these Intoxication occurs primarily in plants can usually be obtained cattle only after large amounts of from the local county agricultural this plant have been eaten over ex- agent. Help with poisonous plant tended periods. Signs of poisoning problems can also be obtained include partial or complete blind- from local veterinarians. ness, inability to use the tongue, and aimless wandering.

Jimsonweed. Tansy mustard.

106 Noxious Weeds Some noxious weeds can be found growing in crops and may be A noxious weed is any plant that harvested with hay or small grains. is designated by a Federal, State, Care must be taken when these or county government as injuri- crops are fed to livestock. ous to public health, agriculture, recreation, wildlife, or property Most of these plants are aggressive and must be controlled by the legal and spread rapidly. It is important owner of the land on which it ap- to monitor all range and pasture pears. There are several poisonous land for poisonous and noxious plants that have also been classi- plants to prevent infestations and fied as noxious weeds. The follow- manage these plants. Early treating is a partial list: ment to control these plants is the most effective. The spread • Mustards: white top, hoary of noxious weeds may signal the crest, perennial pepperweed. decline of entire ecosystems. They Tansy mustard has not been severely affect the biodiversity of declared noxious as yet. natural areas and cause economic • Knapweeds: diffuse, Russian, losses to those relying on range spotted, squarrose, yellow resources. star thistle • Leafy spurge • Goatsrue • Houndstongue • St. Johnswort • Nightshades: sliver leaf, buffalo bur, black nightshade • Kochia weed • Milkweeds • Johnson grass • Poison hemlock

Under ordinary conditions, these plants are seldom grazed. How- ever, poisoning can and does occur under stress conditions such as on overgrazed pastures or after a frost. Noxious weeds compete with useful forages such as grasses, some legumes, etc. for space, nutrients, and moisture.

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