118 Poisonous Plants

WARD T. HUFFMAN, EDWARD A. MORAN. AND WAYNE BINNS

PLANTS that poison livestock can Many poisonous plants are distrib- grow anyplace, but they are a serious uted so widely over grazing areas of problem mainly in the western graz- limited value in the Western States ing areas where overgrazing has im- that the cost of eradication would be paired or destroyed the good but less much greater than the benefits. A sturdy forage plants. more practical procedure is to remove The poisonous plants usually grow the toxic plants from limited areas, among forage plants and so are avail- including trails and watering places. able to grazing animals. Only a few The method of eradication used would are agreeable to the taste, however, depend on the character and growth and animals avoid the toxic plants habits of the species, the other plants unless there is a shortage of feed and with which the toxic plants grow, and better vegetation. the type of soil. Overgrazing is a major factor in When eradication is impractical, a livestock losses from poisonous plants. system of range and pasture manage- Overgrazing has increased in some ment can be worked out to permit the sections because moisture deficiencies use of the forage crops without exces- have reduced the growth of forage. sive livestock losses. That is largely a Hungry animals feed on whatever is matter of wise control of grazing. available. Poisonous plants often are the first Sometimes harmful plants are har- to start growth in the spring and may vested with the hay and their seeds harm livestock if too early grazing is become mixed with grain. Then practiced. If pastures and ranges are animals can hardly separate the good stocked to full capacity in normal years feed from the bad. Livestock owners and the number of livestock is not have considerable control over condi- reduced in drought years, the usual tions conducive to poisoning by plants. forage can be supplemented with other Some plants contain acute poisons roughage or feed in order to avoid and produce visible symptoms or injury to the existing vegetation and death soon after they are eaten. Others losses of animals from the poisonous may be eaten for some time before any plants. noticeable effects are apparent. Most Another aspect of control is that one poisonous plants may be eaten for a species of animals may avoid certain considerable time with little or no ill plants, or one species may not be in- efi'ects. jured by plants that poison another species. Losses then may be avoided by IT IS NOT EASY to control poisonous permitting only the animals least af- plants in pastures and on the range. fected to graze them. Plowing and cultivation usually eradi- Some examples: Horses seldom eat cate them, but in some areas, such as cyanogenetic plants—plants that can the western grazing lands, these meth- produce hydrocyanic acid—in toxic ods are not feasible because of expense, amounts, but cattle and sheep fre- the time they take, and the amount of quently do eat such plants and arc benefit. Sometimes the plants are poisoned by them. Pastures that con- pulled up, grubbed out, or killed with tain cyanogenetic plants should be herbicides, but that is slow and expen- used by horses in preference to cattle sive even under favorable conditions. and sheep. Horses are more frequently Poisonous Plants 119 poisoned by ragworts or groundsels, low a change of feed, especially if which are species of Senecio, than are green feed is available; good care, with cattle or sheep, and sheep are less sus- plenty of water and the right kind of ceptible to their poisoning than are feed, will do much to hasten recovery. cattle. Pastures containing ragworts (Later we suggest treatments for three should be used by sheep in preference types of poisoning.) to cattle or horses. Cattle often are It is well to know something of the poisoned on larkspur. Sheep, however, chemistry of the poisonous elements, can consume large amounts of larkspur especially those in the compounds that without being poisoned but with ap- are physiologically active. Knowing parent benefit. Only under abnormal whether the substance is an alkaloid, conditions are sheep ever poisoned by a glucoside, or something else makes larkspur on the range. Florses never it possible to determine by laboratory eat enough of the larkspur to produce examination whether a sample of the any ill effects. Pastures containing lark- plant is potentially deadly and to de- spur should be used by sheep and tect the poison in the tissues of animals horses but not by cattle. so that a diagnosis can be made in ob- Another aspect: SoQie plants, such as scure or doubtful cases. the sorghums, become toxic under cer- tain conditions. Sorghum in the mature ALKALOIDS are substances that are stage docs not contain any appreciable like the alkalies. An alkaloid turns red amount of potential hydrocyanic acid, litmus paper blue, reacts with an acid but the young plants, or suckers (young to form a salt, and has some other prop- branches from the roots), of mature erties that solutions of the alkali metals sorghum may contain very much po- have, such as soda or potash. tential hydrocyanic acid. Arrowgrass The alkaloids are organic substances grown on water-covered or very wet that contain nitrogen. Some of the soil is far less poisonous than arrow- alkaloids are quite stable and may be grass that continues to grow on soil detected by a chemist in the plant tis- that has dried after the water has re- sues or the tissues of poisoned animals. ceded. Oil meal made from immature It is important for the farmer or stu- flaxseed is more apt to be poisonous dent to know that certain groups or than oil meal made from thoroughly families of plants, such as the legume, ripe flaxseed. lily, buttercup, potato, and some other families, are more likely to contain TREATMENT OF ANIMALS poisoned by alkaloids than some other groups. plants usually is unsatisfactory and Some of the groups do not so metab- useless, because most of the damage olize their nitrogen as to yield alka- may have been done by the time the loids. The large and important mint poisoning is discovered. family seldom contains any alkaloid al Certain feeds or medicines that have plants. The aster, or composite, family some preventive value are described is another nonalkaloidal group, al- later in connection with plants that though there is an outstanding excep- contain selenium. Good care and a tion in the ragworts, or groundsels, of symptomatic treatment (treatment that family. The grasses are not char- that will reduce symptoms) will save acteristically alkaloid bearing, al- some poisoned animals. The outcome though darnel yields loliine, which is a in each case depends largely on the true base. amount of toxic material that has been A well-known alkaloid is strychnine, eaten and assimilated. Treatment usu- which is obtained from poisonnut ally is directed toward eliminating {Strychnos species), a member of the any of the toxic substance that still logania family, whose members are remains in the digestive tract. In mostly tropical plants. Morphine is an chronic poisoning, recovery may fol- alkaloid that can be separated from 120 Yearbook of Agriculture 1956 the drug opium (an extract from and by other local names, belong to certain kinds of poppy). Other well- the legume family. Some species are known alkaloids are atropine, nico- harmless, at least at some stages of tine, and solanine, from the potato growth, and are excellent feed for family; aconitine and several alka- grazing animals. Others are danger- loids of the larkspur group, from the ous at certain times. Some are toxic at buttercup family; zygaclinine and any stage of growth. colchicine, from the lily family; and The alkaloids in lupines have the physostigmine, lupinine, and other peculiarity that slight alterations in lupine alkaloids, from the legume, or the molecular structure may convert pea, family. Names of alkaloids usually the toxic alkaloid into a comparatively end in "-inc." nonpoisonous substance, and vice Alkaloids occur in many stock- versa. The alterations may take place poisoning plants. Among them are the in the plants and may account for the larkspurs, lupines, deathcamas, ground- variations in the toxicity of the grow- sels, Dutchmans-brceches and other ing plants. plants of the Dutchmans-breeches fam- Reports from Germany in the 186o's ily, poison-hemlock, wildtobaccos, cro- attributed great losses to the yellow tolarias, and African-rue. lupine {Lupinus luteus) and other Larkspurs seem to attract cattle lupines. Actually, however, the losses because of the pleasant acidity of their were due to molds. In this country leaves, which is refreshing in hot losses from lupines have been due to weather. They are one of the few alkaloidal poisoning. poisonous plants that are palatable. Deathcamas (species of ^igadenus) The larkspur alkaloids are complex. arc another group of alkaloid-contain- Delphinium harbeyi, one of the tall ing plants. They are grasslike and not larkspurs, and JD. menziesi, a low conspicuous until they bloom. They species, are the main poisonous species, are also known as the poison scgo, although most of the species of Del- mystery-grass, lobelia, soap plant, phinium are dangerous, especially when alkaligrass, waterlily, squirrel food, the plants are small or when they are wild onion, and hog's potato. available in quantities. D. occidentale, a Species of Senecios, or groundsels, tall and comparatively nontoxic lark- have caused a number of losses in live- spur, resembles Z). bar bey i and often is stock in Texas and other States. mistaken for it, D, occidentale contains Among the other alkaloidal plants about I percent of an alkaloid. there are many in the fumitory, or A treatment recommended for cattle Dutchmans-brceches, family {Fuma- poisoned by larkspur during drives and riaceae). Two examples are fitweed roundups is a subcutaneous injection {Corydalis caseana) and Dutchmans- of a mixture of i grain of physostig- brceches {Dicentra cucullaria, sometimes mine salicylate (also called escrine), called Bikukulla cucullaria). In the 2 grains of pilocarpine hydrochloride, carrot family is poisonhemlock or and one-half grain of strychnine sul- spotted hemlock {Conium maculatum). fate, thoroughly dissolved in sterile One member of the potato, or water. This formula applies to an ani- nightshade, family is wildtobacco mal weighing 500 to 600 pounds. For {Nicotiana atlenuala). A member of the a larger steer or cow of 1,000 pounds legume family is crotalaria or rattle- or more, the dose should be twice that box {Crotalaria sagittalis). A member of amount. The medicine relieves consti- the caltrop family is Peganum harmala. pation and stimulates respiration. The materials can be obtained from a GLUGOSIDES contain various sugars druggist. that are combined in the molecule and can be split out by acids and then de- LUPINES, also known as bluebonnets tected by chemical reagents. The Poisonous Plants 121 breaking apart of a glucoside molecule demis sa); sorghum {Sorghum vulgäre); is a complicated technical process. Sudangrass {Sorghum vulgäre var. sudan- The definition of a glucoside in a ense); Johnsongrass {Sorghum halepense); medical dictionary may be helpful: fiax {Linum usitaiissimum); and arrow- "Chemically a glucoside may be de- grass {Triglochin marítima and T. fined as a carbohydrate compound palusiris). formed by a union of a sugar with a non- Wild chokccherry and other wild- sugar accompanied by the elimination cherries are always a potential danger of water." A chemist refers to the non- in spring and early summer for animals sugar as an aglycone. It can be seen that are unusually hungry, but like there is some comparison between the most poisonous plants they may be structure of a glucoside and the struc- eaten in small amounts without caus- ture of a salt, but the organic compo- ing injury. The leaves of the wild- nents of a glucoside are more confusing cherries contain prunasin, a glucoside. than what we consider the simple inor- In the seeds this is associated with ganic components of a salt. another cyanogenetic glucoside, amyg- Flax contains the glucoside lina- dalin, which also occurs in bitter al- marin, which, when hydrolized (water monds and in peach kernels. added), yields acetone (a ketone), glu- The sorghums—Sorghum vulgäre^ cose (a sugar), and hydrocyanic acid Johnsongrass, and Sudangrass—have a (the poisonous principle). cyanogenetic glucoside known as dhur- In a similar way cherry seeds, or pits, rin. Sorghums grown under ordinary contain the glucoside amygdalin, conditions are considered good feed, which, when hydrolized, yields benz- but when the normal growth has been aldehyde (an aldehyde), glucose, and interrupted by drought, frost, tram- hydrocyanic acid. pling, or other causes, hydrocyanic Esculin is a phenolic glucoside from acid may develop to a point where the the horsechestnut. Dhurrin is a cyan- plants become toxic. ogenetic glucoside from sorghum. The amount of hydrocyanic acid that Githagin is a glucoside called a saponin the sorghums can develop varies con- from corncockle. The characteristic siderably according to conditions and ending of names of glucosides is "-in." varieties. Young and second-growth A chemist often can readily detect plants can develop larger amounts than a glucoside or its aglycone, either or older plants. The amount of hydro- both of which may be poisonous. cyanic acid diminishes more or less The plants that owe their poisonous regularly as the plant matures. When properties to such substances are many the seed heads are well formed, the and diverse. Some form soapy solutions plants generally cannot cause fatal poi- with water and therefore have been soning. A possibility always exists that called saponins. Others are called cyan- young suckers or branches or second- ogenetic glucosides because they de- growth plants grow in the field as some velop hydrocyanic acid, or prussic plants are maturing; poisoning may acid, in certain circumstances. Others result if livestock are allowed access to are outside these two categories. them. The stubble that sprouts after The cyanogenetic glucosides have harvest is high in hydrocyanic acid. been responsible for large losses of live- Arrowgrass growing where there is stock in many sections of the United plenty of water is only slightly toxic, States. Many plants have cyanogenetic but under drought conditions it may characteristics, but usually only a few become toxic. are dangerous to livestock. When cyanogenetic plants are made The more important of the cyano- into hay, most of the hydrocyanic acid genetic plants include wild choke- supposedly volatilizes or evaporates. cherry (Prunus virginiana, P. virginiana One has to be careful, however, for var. melanocarpa, and P. virginiana var. occasionally the hay may retain enough 122 Yearbook of Agriculture 1956 acid to make it dangerous, especially times get into wheat and make it dan- for hungry animals that may overeat. gerous to feed to poultry and livestock. Wild flax and wild lima beans con- Rubberweeds, both the bitter rub- tain a cyanogenetic glucoside known berweed, or bitter actinea {Hymenoxys as linamarin or phaseolunatin. Wild odor ata) ^ an annual in the Southwest, lima beans, imported into France as and Colorado rubberweed, or pingue feed for cavalry horses during the First {H, richardsoni), a perennial of the World War, caused several outbreaks Rocky Mountain area, contain sapo- of poisoning. Cultivated lima beans usu- nins. Both rubberweeds are poisonous ally are not dangerous in the United to stock. Sheep especially have been States, because they contain little poisoned by them. or no hydrocyanic acid. One or two The nightshade group, particularly cases of supposed hydrocyanic acid the genus Solanum, may have a saponin poisoning in cattle as a result of feeding (solanine) that contains basic nitrogen ensilage made from lima beans have and so acts also as an alkaloid. Solanine been reported. occurs in sprouted white potatoes A number of factors influence the (which belong to the nightshade fam- absorption of hydrocyanic acid from ily) and has at times caused poisoning plants in the digestive tract, but the of persons who have eaten the tubers. rate at which such plants are eaten and The toxic effects of buUnettle {Solarium the amount of food already in the carolinense) and bittersweet {S, dulca- stomach are probably the most im- mara)—and, somewhat doubtfully, of portant. black nightshade {S. nigrum)—are at- Hydrocyanic acid acts so rapidly tributed to solanine. that there is little chance for remedial treatment. If the victim can be reached RESINOIDS, a large group of some- in time, however, a combination of what indefinite substances, occur in sodium thiosulfate and sodium nitrite some plants. One of the most common injected into the lining of the abdomen is andromedotoxin, a poison, in erica- or into the veins is cflective against ceous plants. A complex substance, it doses of hydrocyanic acid up to three is considered the active principle in minimum lethal doses. (It is considered some of the rhododendrons and azaleas that the minimum lethal dose of hydro- and possibly the laurels. We have no cyanic acid is I milligram per pound precise knowledge of the peculiar struc- of animal—a loo-pound animal may ture of the molecule involved in the be killed with loo mg. of HCN.) toxic action. Waterhemlock {Cicuta Poisoning by cyanogenetic plants vagans), an extremely poisonous plant, may cause rapid respiration, depres- contains a poisonous resinoid. sion, stupor, convulsions, cyanosis of Milkweeds {Asclepias species) contain the mucous membranes (which causes resinoids. Little is known about the them to turn blue), and paralysis. chemistry of the milkweeds, but some Death may follow in a few minutes or investigators have concluded that a several hours. resinous substance extracted from milk- When one animal in a group pastur- weeds produced typical cases of range ing on plants that might be dangerous poisoning when fed to animals. They shows symptoms of poisoning, the did, however, find other substances of others should be removed promptly a slightly toxic nature. from the pasture. Among the species that have been Studied are Asclepias suhverlicillata^ the THE SAPONIN-CONTAINING plants in- whorled milkweed of the Southwest; clude some that are highly dangerous. A. eriocarpa, the broadleaf (wooly-pod) The seeds of corncockle {Agrosiemma milkweed of California; A. fascicularis, githago), a troublesome weed, contain a the whorled milkweed of the Western mixture of saponins. The seeds some- States; and A, pumila and A. veriicillata Poisonous Plants 123 var. geyeri, the whorled milkweeds of wood {Sarcobaiusvermiculatus)^ and other the Central and Eastern States. The plants. The oxalic content of the dried toxicity of the different species varies leaves and fine stems of greasewood greatly and ranges approximately in may exceed 10 percent in late summer the order in which we list them. and early fall. Halogeton may contain Losses from the whorled milkweed 18 to 20 percent. (A. subverticillafa) of the Southwest can Cattle and sheep are susceptible to be severe. Once, near Hotchkiss, Colo., poisoning by greasewood and haloge- 400 sheep died within 24 hours after ton. Most of the losses have occurred feeding on the plant. In 1917 a loss in bands of hungry sheep that have of 736 sheep out of a band of 1,000 been grazed in places where these near Cor tez, Colo., was traced to the plants predominate and desirable for- same species. Next to waterhemJock, age is scarce. Animals may eat small this whorled milkweed has been con- amounts of the plants daily over a long sidered the most toxic plant in the period of time without apparent injury. United States, but another species of À sheep that eats them slowly all day milkweed. A, labrijormis^ is much worse. with other forage may safely consume The toxicity of ^4. lahriformis is highest twice the amount that would be toxic during the early part of the growing if eaten in an hour without other for- season, when about i ounce of its green age. The animals can eliminate the leaves can kill a sheep weighing 100 oxalates fairly rapidly and thus prevent pounds. The lethal amount for cattle the accumulations of toxic levels is even less in proportion to weight. within the body. With good manage- The plant loses some of its toxicity at ment of ranges and livestock, especially maturity, but the dry leaves retain during trailing and following shipping, enough of the toxic substance to cause losses from poisoning by greasewood heavy losses of livestock in winter and and halogeton can be kept down. early spring. Books giving antidotes to poisons Apparently A, lahriformis grows only recommend either chalk (which is in eastern Utah, mostly in sandy places mostly carbonate of lime or calcium and along watercourses. This species, carbonate), or limewater as an anti- like other poisonous milkweeds, is not dote for oxalic acid poisoning. The palatable. Animals eat it only when lime forms an insoluble compound they have no other feed. On over- (salt of lime) called oxalate of lime grazed ranges and trails it is a hazard (calcium oxalate). When formed in the at all times. intestines, the compound would be We know of no remedy for milkweed eliminated as an insoluble compound poisoning. If losses are to be avoided, with the feces instead of being absorbed hungry animals must be kept away into the blood stream as might be the from places in which poisonous milk- case if it were either oxalic acid or weeds grow or the plants should be oxalates (salts) of other elements prev- eradicated. alent in most foods and vegetation, The symptoms of milkweed poison- such as sodium (forms oxalate of soda ing are uneasiness; some lack of muscu- called sodium oxalate) and potassium lar coordination; rapid, shallow, noisy (forms oxalate of potassium called respiration due to edema (swellings potassium oxalate). Both are water- filled with fluid) of the lungs; spasms; soluble salts of oxalic acid. and considerable struggling. Death In one experiment, however, with a may result from respiratory failure. sheep poisoned on halogeton, we gave The kidneys usually are affected more the animal some chemically pure cal- than the other organs. cium carbonate as an antidote. It did not prove so effective as in another OXALIC ACID occurs in sorrels, docks, experiment, when the antidote we gave halogeton (Halogetonglomeratus), grease- was the leaves of alfalfa hay. Possibly 124 Yearbook of Agriculture 1956 the lime in the alfalfa hay was more them in large quantities. Some crop soluble and consequently more reac- plants and others tolerate selenium in tive with the oxalic acid (to form an the soil and may absorb selenium and insoluble salt) than was the lime in the metabolize it in their tissues in cjuanti- calcium carbonate. ties that would make them poisonous Tremetol produces a disease known to livestock if eaten in sufficient quan- as trembles in livestock and milksick- tity. ness in people. Tremetol, an oily Experimental work with laboratory alcoholj can be isolated from white animals indicates the resistance of ani- snakeroot (Eupatorium rugosiim), which mals to selenium poisoning is increased grows in the Eastern States, and from by a high-protein diet. rayless goldenrod or jimmy weed {Ap- Research workers in Wyoming lopappus heterophyllus)^ which grows in learned that increasing the protein and the Southwestern States. vitamin A intake of sheep improves the Cases of trembles or milksickncss quality of the diet to the extent that have been reported in Virginia, North the poisonous effects of selenium are Carolina, South Carolina, Georgia, lessened. If the selenium intake was Maryland, Missouri, and Michigan, reduced or stopped and a high protein where Vv^hite snakeroot grows, and in diet was continued, the animals re- Texas, New Mexico, and Arizona, covered from selenium poisoning with- where rayless goldenrod grows. in a short time and the selenium was Milksickncss has been caused by completely eliminated in about 30 milk and by butter made from milk days. If the protein content of the diet of cows that had fed on tremetol-con- was low, however, the recovery was taining plants. The isolation of treme- slow or the animals died. It w^as found tol and the production of trembles by also that iodine increases the suscepti- feeding poisoned butter to sheep com- bility of animals to selenium poison- pleted the chain of evidence linking ing. The recommendation was made the plants to milksickncss in human that in places where selenium occurs, beings. salt that contains no iodine should be used. NITRATE POISONING in animals has Arsenic compounds, especially com- been reported to be caused by animals pounds with sodium, tend to protect eating oat hay, Russian-thistle {Salsola animals against the toxic action of pestifer), tar weed {Amsinckia intermedia) ^ selenium. In one experiment, a group redroot pigweed {Amaranthusretroßexus), of steers that were given 25 parts per puncturevine (Tribulus terrestris), beet million of arsenic in the salt made bet- tops (Beta vulgaris), white ragweed ter gains and sold for higher prices {Fraseria discolor), variegated thistle than others. {Silybum marianum), and many others. Selenium poisoning is mentioned in another chapter (p. 117). SELENIUM is a nonmctallic element. Some compounds of molybdenum (a Chemically it resembles sulfur, how- heavy metal that belongs to the chro- ever, the physiological action of sele- mium group), are soluble and may be nium is different from that of sulfur. absorbed by plants so as to make them Selenium-bearing plants sometimes harmful to stock that eat them. We cause considerable damage. Some discuss these compounds under the plants known as indicator plants, term "molybdenum." which seem to require selenium in the A discussion of molybdenum poison- soil for their growth, such as princes- ing appears in a previous chapter (p. plume (Stanleya species), woody aster 115). (Xylorrhiza parryi), and some species of English stockmen have known for a Astragalus, contain considerable sele- long time that certain pastures, which nium and poison the animals that eat they called "teart," were harmful to Poisonous Plants 125 Stock. The tcartncss was especially prev- storage. Legumes in general absorb alent in Somerset, and they became more molybdenum than nonlegumes. known as the 'Heart pastures of Somer- The greatest concentration is found in set." The outstanding symptom of most instances in the blades of the cattle grazing teart pastures was scour- leaves and in the actively growing ing, or diarrhea. Affected animals also parts of the plant. That fact may ac- might show emaciation, anemia, stiff- count for the beneficial effect of feed- ening or enlargement of the joints, dry ing roughages to reduce excessive skin, and loss of coat color or hair. scouring to which cattle are subject Black tended to become gray, red be- when they graze succulent leguminous came tan, and white became a light pastures. tan. This discoloration was first noticed Molybdenum is widely distributed around the eyes and the ears. Young, in the soils of many places in the growing cattle were more susceptible United States. Most of the reports of to the teartness of pastures than old trouble that we have had have come cattle. from San Joaquin Valley, although the Several possibilities were mentioned molybdenum in the troublesome soils to explain the disease, but the real there is not always high. It may range cause of the trouble was shown in 1938 from 1.5 to 10 p. p. m., and most of it to be an excess of molybdenum in the is soluble. The high solubility of those vegetation. Studies were started later soils is due mainly to their alkaline in Europe, Australia, the islands of the reaction, for water soluble molybdenum Pacific, and the United States. has been greatly reduced by acidifica- The first recorded molybdenosis (a tion. In this respect molybdenum be- condition of stock effected by excess haves as selenium does, and the op- molybdenum in their feed) in the posite of manganese, boron, zinc, and United States was from an area of the copper. Soils that are overlimcd be- San Joaquin Valley of California by J. come alkaline and may produce toxic W. Britton and H. Goss less than 10 vegetation even in humid regions if years after the discovery in England. the soil contains enough molybdenum. According to the early reports on The toxicity of molybdenum to molybdenosis, any pasture whose vege- animals seems to be due at least tation contained 20 p. p. m. (parts per partly to an imbalance of nutrients or million) of molybdenum or more was minerals in the animals' system. Re- a dangerous one. Recent studies show search in Australia revealed that the that a certain amount of molybdenum symptoms of animals with excess in the vegetation or in the soil is not molybdenum resemble the symptoms the only factor to be considered as the of a disease known as peat scours, cause of the disease or the toxicity of which affects animals pastured on peat the pastures. The acidity of the soil, soil and occurs in animals that have a the species of plants, the stage of deficiency of copper. Symptoms of growth of the plants, the part of the copper deficiency and molybdenosis plant eaten, the amount of molybdenum are relieved by giving animals soluble in the soil, the condition of the animals compounds of copper. and the character of any supple- Investigators in England considered mentary food they eat all contribute to that teartness or molybdenosis was a the poisoning of livestock. disease only of cattle. Early investi- Generally speaking, dry hay from a gators in the United States recognized high-molybdenum area is less likely to that sheep also may be affected. It is cause scouring than green, succulent now known that, although it is pastures in the same area. Some primarily a disease of ruminants and alfalfa hay occasionally has caused that field cases of reported molybdenum severe symptoms of molybdenum, but poisoning seem to be confined to hay usually loses its toxicity with cattle and sheep, horses, swine, poul- 126 Yearbook of yigriculture 1956 try, and laboratory animals may be to 100 pounds of animal weight is poisoned if they get too much molyb- lethal for cattle. denum. Nonruminant animals are Most animals that show severe symp- relatively immune to poisoning, how- toms die. Losses may be prevented by ever. providing suitable feed along the trails and on the ranges so that animals are LoGOWEEDS, copperweed, paper- not compelled to eat the toxic plants. flower, horsebrush, bracken fern, and In copperweed poisoning, the liver eupatorium are examples of plants seems to be affected first and the that contain unknown and miscel- kidneys later. The symptoms usually laneous poisons. are marked depression, weakness, and The loco weeds (species of Astragalus coma. Death follows without much and Oxytropis) were so important that struggling. at one time the term '*locoed" was Occasionally an animal shows con- used synonymously with "poisoned," siderable nervousness and excitement. especially in the Western States. Frequently animals arc found dead in The locoweeds have been analyzed the morning without having shown extensively in the past 80 years. White symptoms the previous evening. loco {Oxytropis lamberti) was studied by Greenstem paperflower {Psiloslrophe James F. Couch, who found that the sparsiflora) has become a problem of active principle belongs to none of the sheepmen in northern Arizona. It has recognized groups of poisonous com- been spreading over a wider area, so pounds but appears to be a new type. that it is becoming increasingly diffi- Some members of the genus Astra- cult to utilize the range. Two other galus are nontoxic. Others produce species of Psilostrophe in Texas have poisoning but not the true locoism. caused losses of sheep. Examples of the first group include The paperflower grows in semiarid the red locoweed {A, drummondii) and regions that are used largely as inter- A, tenellus. In the second group is A. mediate and winter ranges. Overgraz- tetrapterus. Nothing is known about ing may have been responsible for its their chemistry. spread. Very likely cattle do not eat Another group of the genus is poison- enough of it on the range to be poi- ous not because of any constituent nor- soned because the paperflower is not mally produced by the plant itself but palatable. In places where the forage because of selenium, which the plants consists largely of plants low in palata- may take up from the soil in the form bility, it is necessary to move the sheep of a compound and accumulate in to uninfested areas as soon as loss dangerous quantities. starts in order to prevent further losses. Copperweed {Oxytenia acerosa) grows Some deaths occur even then after the over much of the Colorado Basin animals are moved. along streams and seepage areas where Because P. sparsiflora is abundant the soil is strongly alkaline. Copper- over a rather wide region, eradication, weed only recently was proved to be even if it could be accomplished, would poisonous. It affects cattle and sheep. not be economically practicable, and The plant increases in toxicity as it the control of sheep losses in the region reaches maturity. Poisoning usually must depend on improvement in range occurs in the fall when the cattle are conditions. That is, the range area being driven down from the summer should be widened so there would be ranges over trails that are overgrazed larger grazing area for each sheep. and contain little or no desirable In paperflower poisoning, the kid- forage. Enough copperweed, which neys appear to be affected primarily. ordinarily is quite unpalatable, may Poisoning is usually the result of feed- be eaten then to cause poisoning. Less ing for several days on the plant. Con- than one-half pound of green leaves sequently the symptons may develop Poisonous Plants Wi rather slowly. The principal symptoms not occur. The same is true of sheep are loss of appetite, depression, and kept in total darkness after eating weakness. Death follows a week or Tetradymia. The exact nature of the more of partial coma. substance causing photosensitization Horsebrush is the name of two re- and the manner in which it gets into lated plants. One is called littleleaf the circulation near the body surface horsebrush, spring rabbitbrush, or coal are not known definitely. oil brush {Tetradymia glabrata) and has The areas where bighead occurs been known for many years as a cause correspond with the distribution of of heavy losses of sheep. It is common the species of Tetradymia. but although in dry areas of western Utah, Nevada, the plants are the main cause of big- eastern California, southern Oregon, head, other factors are involved in the and southwestern Idaho. occurrence of the disease. The kind Spineless horsebrush (T. canescens) is and character of the feed on which poisonous to sheep, but rather large the sheep subsist at the time they eat amounts are necessary to produce poi- the plants are probably the most im- soning. It grows to a limited extent in portant factors in producing the edema the same areas as those occupied by or photosensitization. Horsebrushes are littleleaf horsebrush. It is found in among the first to begin growth in the greater abundance at the higher ele- spring and usually are well leaved out vations and extends through central by the time sheep start on the trails Utah to southwestern Wyoming, south- to the shearing corrals and summer western Montana, eastern and south- ranges. Most of the bighead outbreaks ern Idaho, eastern Oregon, eastern occur at that time. Washington, eastern California, and Since plants are not palatable and northern New Mexico. are seldom eaten in toxic amounts The most toxic stage of both plants when good forage is available, sheep is during their active growth period— may graze normally in an area where April and May for littleleaf horsebrush Tetradymia is abundant with a very and May and June and early July for little danger of bighead, but a hungry spineless horsebrush. herd that is being trailed through the In sheep the horsebrushes cause a same area may develop the disease. disease known as bighead or swell- Stormy weather also is apt to change head. Bighead is essentially a range the feeding habits of animals to the disease and has been prevalent in many extent that unpalatable or poisonous areas of the intermountain region since plants will be eaten. Early spring use the early days of the sheep industry. It of ranges before the forage plants are probably has caused a greater finan- well started may cause sheep to eat cial loss to the sheep owners in the Tetradymia in sufficient amounts to affected areas than any other disease. produce bighead. Bighead apparently has two sepa- Bighead usually appears quite sud- rate stages—first, a toxic condition denly in a band. Many animals may produced by the plants and affecting become affected within a few hours, primarily the liver; second, a swelling, although symptoms usually appear i6 or edema, which affects principally to 24 hours after the plants are eaten. the head. This edema affects only Prevention of range bighead depends animals with white or light-colored on a knowledge of the distribution of skins and is the result of sensitiveness the Tetradymia plants. Avoiding Tetra- to light. Either white sheep or black dymia areas on the ranges or trails sheep may be affected by the toxic when sheep are hungry will eliminate substance in the plants, but the pig- the greatest danger. ment in the skin of black animals protects them from the effects of the BRACKEN {Pteridium aquilinum) may light rays, so that photosensitivity does be poisonous to both horses and cattle un Yearbook of Agriculture 1956 and may cause rather severe losses. the membranes of the eyes, nostrils, Several species of ferns have been and mouth, and a bloody diarrhea. suspected of being poisonous to live- The symptoms of fern poisoning may stock. Because of their low palatability, vary, but when such a condition is bracken are seldom eaten when other suspected and it is known that the forage is available. Therefore they arc plants are being eaten, a change to not considered of much importance. other feed should be made. The bracken fern occurs in many The mortality rate of animals show- parts of the United States, especially ing symptoms of bracken poisoning is in moist places and in meadows. usually high. Some benefit may be Most of the cases of bracken poison- derived from treatment of the symp- ing in horses have been caused by ferns toms, such as a diet of readily available that were cut and cured in meadow soft, nutritious food to relieve exertion, hay. Poisoning in cattle usually is the constipation, and irritation of the result of grazing on the green plants hemorrhagic intestine, but no specific when other forage is scarce. Hay con- cure is known. Prevention is the best taining ferns is more dangerous in way to control the disease. winter if it is the only feed. Poisoning from green plants usually occurs dur- LIMESTONE DISEASE of southern New ing the latter part of the grazing Mexico and southeastern Arizona, season until frost. which has resulted in heavy losses of Bracken poisoning does not usually cattle over a period of years, is prob- occur until after the animals have been ably caused by Wrights eupatorium feeding on ferns for 3 or 4 weeks, {Eupatorium wrightii). The nature of its unless the feed consists very largely toxic substance has not been deter- of these plants. When large daily mined. Unlike white snakeroot {E, amounts are consumed, the symptoms rugosum), a related and highly toxic may appear earlier and be more acute species of the East Central States, than when the ration contains less of Wrights eupatorium does not contain the toxic material. tremetol. The toxic substances in the ferns ap- Toxicity is confined principally to parently have a cumulative effect, so the leaves, and the margin between a that a period of time must elapse before nontoxic and a lethal dose is very nar- symptoms become noticeable. The row. Poisoned animals are usually course of the disease and the severity of found dead on the range, having died the symptoms largely depend on the during the night while lying in a nor- amount of the plants consumed daily, mal position without any signs of although there is some variation in the having struggled. The plant is as toxic individual susceptibility of different during the summer as later, but appar- animals. ently it is not eaten until fall; the losses The symptoms of bracken poisoning start about the time of the first heavy in horses may be emaciation, weakness, frosts and continue for a month or staggering, nervousness, and constipa- longer. In experimental feeding, sheep tion. The temperature may remain were found to be as susceptible as nearly normal, although the pulse rate cattle to the poisonous cflTects of the is usually higher. The disease may plant, but the reported losses have all extend over a week or more. The been among cattle. appetite may remain fairly good for Wrights eupatorium is found mainly some time after symptoms appear. in limestone outcroppings on ridges The symptoms in cattle are usually and slopes of foothills and lower moun- more acute and may include a high tains. These areas may occupy only a temperature, rapid loss of flesh, saliva- small portion of a pasture and, if tion, hemorrhage from the nostrils, fenced on', the remainder of the pasture small hcmorrhagic spots (petechiac) in would be safe for cattle. If additional Poisonous Plants 129 fencing is not feasible, the cattle should The first published report we have be moved to other pastures shortly on the effect of fescue is one by I. J. before the first of October, Cunningham, of Wallaceville, New Zealand, in the New Zealand Journal TALL FESCUE {Festuca arundinaceae) of Agriculture, November 1948, page has received attention lately as a pos- 519. Dr. Cunningham reported in the sible cattle-poisoning plant. We have Australian Veterinary Journal, Febru- not been able to learn v^'hat is its ary 1949, that the fescue grass under poisonous principle. consideration should be classed as a Tall fescue, a coarse, recdlikc grass, toxic plant and not as a plant that ac- is a prominent grass crop in some quired toxicity through infestation by swampy areas of New Zealand. In ergot. areas where this fescue grew, some cat- After they received the reports from tle in the fescue pastures became New Zealand and Australia, research affected with a condition in which workers in the United States under- lameness sometimes developed within took to determine whether some 14 days after they first ate the fescue. trouble in the United States that had One or both hind limbs were involved. been attributed to the ergot actually Heat, swelling, and pain occurred in might have been caused by fescue. the affected limb. Later the pain and the swelling subsided, but drying and LAMENESS IN CATTLE that had been hardening of the skin and cold in the eating fescue had been reported at extremity of the leg or foot set in. An various times by cattlemen in western indented line form.ed in the hide of the Colorado. They believed it was due to leg, which separated the lower part of ergot poisoning, foot rot, or frozen the leg and foot, which was cold and feet, but after the reports came from apparently dead from the normal skin New Zealand, the disease was asso- above. The warm and cold places ciated with fescue. usually were sharply separated at this Festuca arundinaceae is often referred point. Sometimes the extremity of the to as tall fescue, but other common limb was shed. names for it are alta fescue, king fescue, Such a description is like a descrip- giant fescue, ditchbank fescue, and tion of poisoning of cattle by the black, reed fescue. A. A. Goodman, exten- hard, hornshaped sclerotia (horny sion veterinarian of the Colorado mass of fungus tissue) that form the Agricultural and Mechanical College, resting stage in the growth of the ergot in an early report of the trouble in fungus. Because ergot sclerotia com- Colorado expressed the opinion that monly replace some of the seeds of other more palatable species of fescue many grasses on which they grow (they grasses, which are recommended for often replace rye grains in the head), pasture grass mixture, do not carry the it was thought it was ergot of the tall toxic substance which was reported to fescue that was causing the trouble in be in the coarse tall fescue. New Zealand. Dr. T. J. Stearns, a practicing That assumption was readily made veterinarian in Louisville, Ky., in an from the similarity of symptoms of article in the Journal of the American ergot and fescue poisoning. The ergot Veterinary Medical Association, May sclerotia forms only in the seed heads 1953, page 388, reported a similar ail- of a grass which it infects. Study and ment among cattle grazing fescue 31, observation led to the discovery that a smaller more palatable variety. He the cattle-foot condition occurred in wrote: "It would seem that most fescue places where there were no seed heads species of grasses contain the toxic of fescue and that consequently the substance, and under certain climatic poisoning from fescue could not be as conditions will cause trouble." a result of the er,srot. Other references to fescue foot or 3GC3()4°--5C- -10 130 Yearbook of Agriculture 1956 fescue lameness, as the disease is often livestock poisoning by plants from igjS until called, have come from Tennessee, his retirement in 1955- Alabama, California, and Texas. Re- EDWARD A. MORAN, an animal physi- search workers in Colorado, Ken- ologist in Noninfectious Diseases Section of tucky, and Tennessee began experi- the Animal Disease and Parasite Research ments in an effort to determine the Branch, has been studying stock poisoning causative agent and develop a cor- plant problems as an employee of the De- rective treatment. partment of Agriculture since ig2g. Until A report from the Tennessee Agri- igji his field quarters were in Utah cultural Experiment Station said that during the summer. He is a graduate of the cattle have recovered when removed New York State College of Agriculture at from fescue to other pastures, some- Cornell University, times slowly and after loss of con- WAYNE BINNS holds degrees from Iowa siderable weight. Some of the recovered State College and Cornell University, He animals were returned to the fescue was a member of the veterinary science pastures without recurrence of tox- department of the Utah State Agricultural icity symptoms or any further un- College from ig^o to ig42 and head of the toward effects. department from ig^S to ig54. He joined The report stated, "Based on the the Agricultural Research Service as a lack of complaints from farmers and veterinarian in charge of studies of livestock Extension people, many fescue pas- poisoning by plants in ig§4 with head- tures may not be toxic." Because of quarters in Logan, Utah. the large number of pastures of tall For further reading: fescue on which cattle graze and the J. W. Britton and H. Goss: Chronic Molyb- small number of cases reported, the denum Poisoning in Cattle. American Veterinary percentage of toxic pastures may be Medical Association Journal, volume 108, small. It is likely that toxicity in number 828, pages 176-178. 1946. A. B, Clawson: A Preliminary Report on the certain pastures does not persist from Poisonous Effects of Bitter Rubber Weed {Actinea year to year. odor ate) on Sheep, Journal of Agricultural Re- Most of the cases of toxicity from search, volume 43, number 8, pages 693- tall fescue have been in localities 701. 1931. A. B. Clawson, James F. Couch, and H. where because of ecological factors the Bunyea: The Toxicity of Sodium Cyanide and the coarse, persistent plants were nearly Efficiency of Nitrite. Thiosulphate Combination as in pure stands. a Remedy for Poisoned Animals, Washington The danger of toxicity probably can Academy of Science Journal, volume 25, pages 357-361. 1935. . , _ ^ ^ . be reduced considerably by providing James F. Couch, Remhold R. Briese, and a variety of feed rather than depending J, H. Martin: Hydrocyanic Acid Content of on fescue as the only feed. Tall fescue, Sorghum Varieties, Journal of Washington even though the palatibility is low and Academy of Science, volume 29, pages 146- 161. 1939. the danger of poisoning from it has to M. W. Emmel: The Toxic Principle of the be considered, serves a purpose be- Tung Tree, Florida Agricultural Experiment cause of its hardiness, persistence, and Station Bulletin 431, 35 pages. 1947. tolerance of swampy conditions. C. E. Fleming, M. R. Miller, and L. R. Vawter: The Fitweed {Capnoides caseana) A If vigilance and careful observation Poisonous Range Plant of the Northern Sierra is made for initial symptoms and Nevada Mountains, Nevada Agricultural Ex- the cattle are removed promptly from periment Station Bulletin 121, 29 pages. pastures, possibly tall fescue has a W. J. Pistor, J. C. Nesbitt, and B. P. Car- useful place under certain conditions don: The Influence of High Salt Intake on the Physiology of Ruminants, Proceedings Book, as an economic plant for cattlemen. American Veterinary Medical Association, Eighty-Seventh Annual Meeting. 1950. WARD T. HUFFMAN, a veterinarian in W. E. Rand and H. J. Schmidt: The Effect Upon Cattle of Arizona Waters of High Fluoride the Animal Disease and Parasite Research Content, American Journal of Veterinary Re- Branch, Agricultural Research Service, since search, volume 13, number 46, pages 50-61. igo8, was in charge of the investigations of 1952.