10 RANGELANDS 19(3), June 1997

Larkspur Poisoning in Livestock: Myths and Misconceptions

Anthony P. Knight and James A. Pfister

arkspurs (Delphinium spp.) are pertain to tall larkspurs as most re- doubtful if cattle could consume major causes of cattle deaths on search has been directed at these enough root material for toxicity to Lmountain ranges during the sum- species. When appropriate, we also occur. Marsh et al. (1916) fed 2.4 lb. of mer grazing seasonin the western U.S. have made comments about low lark- low larkspur roots alone to a cow with- For descriptive convenience, larkspurs spurs. out effect; mixtures of roots and plant are grouped into tall and low species tops were also fed to cattle (up to based upon their growthcharactenstics. Myth #1: ConsumptIon of larkspur about 20 lb./day) without effect. In col- Tall larkspurs are generallyfound grow- roots causes many cattle deaths. lecting samples to determine the toxic- ing at high altitude and reaching 4 to 6 Tall larkspurs are sometimes eaten ity of tall and low larkspurs, livestock feet in height. Tall larkspurs are most avidly by cattle during or just after sum- managers need to sample only above- commonly represented by Delphinium mer storms, and cattle deaths have ground portions of the plant. barbeyi, D. glaucescens, D. glaucum, been attributed to consumption of tall and D. occidentale. Low larkspurs (D. larkspur roots when the soil is wet. Tall Myth #2: Cattle eat tall larkspur nuttallianum, D. virescens, 0. ander- larkspurs have a very fibrous root because they crave salt or other soni,) seldom grow above 2 feet in crown that is impossibleto completely minerals. height, while plains larkspur (D. geyen) extricate from the ground without a Some ranchers believe that cattle is intermediatein growth habit. shovel or similar tool. At times, such as may be attracted to tall larkspur be- As the livestock industry moved when the soil is wet, one can pull on tall cause of a craving for salt or other westward beyond the Mississippi River larkspur stems, and a small portion of minerals suchas phosphorus.This be- into the Rocky Mountains in the root will be uprooted with the stem. lief has led to widespread claims for 1830's, livestock began to die of plant Most of the time when pulling on tall feeding mineral salt supplements to poisoning. Larkspurs were eventually larkspur stems, however, the hollow reduce tall larkspur losses. Broadleaf recognized as a serious problem, and stems break above ground level. plants (i.e., forbs), including larkspur, in 1885 the USDA's Bureau of Animal Literally hundreds of hours have been usually contain higher concentrations Industry began investigating larkspur spent observing cattle eat tall larkspur of minerals than do grasses. Forbs, and other poisonous plants. Larkspur in wet and dry conditions, and never besides tall larkspur, are always a research centered in Colorado be- has a grazing animal been seen eating major component of cattle diets during cause of the magnitude of the losses roots. Marsh et al. (1916) attemptedto summer on mountain ranges, and it is in that state. C.D. Marsh and cowork- poison a sheep with tall larkspur roots: unlikely that cattle grazing on most the ers fed tall and low larkspur to more sheep ate about33 lb. of root mate- mountain ranges will be mineral defi- than 100 head of cattle from 1909 to rial over 11 days with no indication of cient if provided with common salt, un- 1911 in Colorado (near Crested Butte) toxicity. The roots of tall larkspurdo less the forage in general is a contain a small amount of toxic alka- lacking and Montana (near Big Timber), and specific nutrient (e.g., copper). described the toxic loids communi- dose, symptoms, (D. Gardner, personal Grazing studies have shown that cattle and experimental therapies (Marsh et cation), but it is unlikelythat tall larkspur do not eat more tall when de- al. Research on tall roots have ever cattle. larkspur 1916). larkspur poisoned prived of all mineral salt supplement has continued to the Immature tall are the toxicity present larkspur plants than cattle which have been supple- day, with significant progress occur- most toxic; leaves and pods containthe mented and Manners in the last concentrationof toxic (Pfister 1991; ring 10 years or so (Pfister highest alkaloids, Pfister and Manners etal. whereasstems are low in 1995). During 1993). toxicity. one year (1990 at Yampa, Cob.) cattle Because of the lengthy history of Low larkspurs (e.g., D. nuttallianum) ate no larkspur although the tall lark- larkspurpoisoning, many myths and are shallow-rooted perennials with a small root low spur contained a high concentrationof misconceptionshave arisen in the live- relatively containing sodium to other Tall stock about various concentrations of toxic alkaloids. We compared forage. industry aspects larkspurmay contain calcium of the problem. In this paper, we out- have seen cattle pull the entire low higher line some that about from concentrations than phosphorus (1.5 myths prevail larkspur plant (including roots) to 3.0% vs. some to and to de- the on a few occasions when 0.30%), leading larkspur toxicity, attempt ground that this imbalance in- bunk these and the ground was wet, but generally cat- suggest may myths misconceptions crease to animals. There is so that livestock producers can more tle eat only the aboveground portions palatability deal with of low Even cattle no indication, however, that the Ca:P realistically larkspur poison- larkspur. though ratio is of in ruminant ing. By necessity, most comments will may ingest an occasional root, it is any significance RANGELANDS 19(3), June 1997 11 diets, as long as neither mineral is de- weeks, often coinciding with the transi- ficient (Ternouth 1991). It is possible tion from preflower to the flowering that cattle that are deficient in a specif- stage of growth. ic mineral may eat more larkspur under some circumstances, but no ex- perimental evidence exists to support Myth #4: Monkshood causes feeding expensive, custom-formulated many cattle deaths attributed to mineral salt supplements to cattle tall larkspurs. grazing larkspur ranges. Excess min- Monkshood (Aconitumspp.) is also a eral salt supplementation seems un- member of the Ranunculaceae(butter- likely to alter the susceptibility of indi- cup) family, and is often confused with tall the form vidual animals since the larkspur larkspur. Though growth toxin(s) binds at receptor sites at the and leaves are similar in appearance,it is to monkshoodfrom neuromuscular junction, and mineral easy distinguish status would not alter tall larkspurs if the plants are flowering. probably binding Monkshood lacks the characteristic affinity. It is possible that supplement- under some cir- spur on the back of the flower that ing magnesium might, its name cumstances, help to reduce death loss gives larkspur (Photo 1). Monkshood has a helmet-like hood from bloat. is un- larkspur-induced It the common over that the of mineral salt (hence name) rising likely question the flower Tall will ever be ade- (Photo 2). larkspurs supplementation characteristically have a hollow stem, quately resolved, given the number of minerals involved and the possible combinations and permutations of mineral salt supplements, forage min- eral concentrations,and variable cattle mineral intake. We recommend that livestock producers consult with a local veterinarian or nutritional consul- tant to determine if their ranges are deficient in specific minerals, and that mineral salt be fed as supplements Photo2. Larkspurflower. Note the charac- necessary to meet nutritional needs, teristicspur on the flower. but not to protect livestock against ef- fects of tall larkspur. whereas monkshood stems are not hollow, containing a pithycenter. Myth #3: Tall larkspur is most Monkshood is not eaten to any great dangerous before flowering. extent by grazing cattle. Grazing stud- Tall larkspur is most toxic when im- ies for several years in areas with sub- mature, and toxicity generally decreas- stantial populations of both tall lark- es with maturity, except with the seed spur and monkshood showed that cat- pods (Ralphs et al. 1997). Numerous tle rarely ate more than a few bites of grazing studies have shown that cattle monkshood, yet ate large quantities of eat little or no tall larkspur before tall larkspur (Pfister, unpublished stems elongate flowering racemes data). In our opinion, if otherforage is (Pfister et al. 1997). Since tall larkspur available, grazing cattle will rarely con- is only dangerous when consumed, sume a toxic dose of monkshood, es- the danger to cattle before flowering is pecially since the quantity of toxic al- not as great as after flowering. There kaloid in monkshood is considerably is a primary toxic window during the less than that found in larkspurs. We flower and early pod stages of growth believe that nearly all deaths in areas when toxicity is declining but palatabli- with tall larkspur and monkshood ty is increasing, resulting in the most growing together can be attributed to dangerous grazing period. Usually tall larkspur. Monkshood poisoning is most cattle deaths occur afteranimals Photo 1. Monkshood flower. Note the reportedly more of a problem in characteristic helmet-likehood rising than in North America. have been in a pasture for a couple of overthe flower, and the lackof a spur. Europe 12 RANGELANDS 19(3), June 1997

However, since monkshood contains similar alkaloids as and given this knowledge it is likely that any apparent suc- those in larkspur, it can produce similar signs of paralysis cess with these early treatments was related to the toxic and death if eaten in sufficient quantity. dose the animal had ingested and not the treatment itself. If less than a lethal dose of larkspur alkaloids was consumed, Myth #5: All larkspurs are equally toxic. the animal would likely recover in spite of any treatment, The toxicity of larkspurs varies depending upon the unless bloat or vomition occurred while the animal was species, and the conditions in which the plants are growing. down. The species that have the highest concentrations of toxic The primary site of action of the larkspur alkaloids is the alkaloids include D. glaucum, D. barbeyi, D. glaucescens, neuromuscularjunction where they reversibly bind to D. geyeri, and D. occidentale (Ralphs et al. 1997). Even acetyicholine receptor sites. This blockage inhibits nerve within a population of the same species of larkspur there is impulse transmission and muscle paralysis develops rapid- variability in the alkaloid content (Pfister et al. 1994). At ly. This is reflected in the progression of clinical signs be- times, plants growing in full sun and under drought condi- ginning with muscle weakness, staggering gait, inability to tions may be more toxic. It is wise to assume that all stand, bloat, respiratory paralysis and death. Any stress species of larkspur, including horticultural varieties, are po- placed on the affected animal invariably hastens its death. tentially poisonous until proven otherwise. Bloating occurs because of the paralysis of the eructation mechanism, and the presence of the highly fermentable Myth #6: Delphinine is the major toxic alkaloid. larkspur in the rumen probably plays an important role in Early efforts to identify the larkspur toxin characterized the high mortality associated with larkspur poisoning. Some delphinine as the toxic alkaloid. In reality, there is no alka- success of early remedies for larkspur poisoning such as loid called delphinine in North American tall larkspurs giving bacon fat and turpentine orally may have been effi- et as (Pelletier at. 1989), Delphinium staphisagria (a cacious in that fat and turpentine can help reduce bloating. European plant) is the only larkspur species found to con- In light of present knowledge about larkspur poisoning, tain delphinine. At least 150 alkaloids have been identified treatment should be aimed at the neuromuscular in reversing larkspurs but the primary toxins are two related alkaloids: blockade by the intravenous administration of physostig- methyllycaconitine (MLA) and 14-deacetylnudicauline mine sulfate. This compound maintains high concentrations (DAN; Manners et al. 1995). Deltaline occurs in greater of the neurotransmitteracetyicholine, thereby restonng nor- quantity than any otheralkaloid in tall larkspurs, but is rela- mal neuromuscular activity. Since bloating is a significant tively nontoxic. The alkaloids MLA and DAN, plus the highly component of larkspur poisoning it is also important to en- toxic alkaloid nudicauline, are the major toxins in low and sure the animal is kept resting on its sternum, and to ad- plains larkspurs. minister appropriate antibloating medication.Above all, it is critical that the animal not be even to the of #7: stressed, point Myth Cattle, sheep, and horses are equally sus- not treating the animal if it requires stressingit. ceptible to larkspur poisoning. Larkspur poisoning has been recognized as a serious Conclusions problem in cattle, sheep, and horses in the mountainous areas of the western United States since the beginning of Many anecdotal stories about tall larkspur poisoning have the There century. is, however, considerable species varia- become accepted as fact by the livestock industry during tion in susceptibilityto the larkspur alkaloids with cattle this century. Research results have shown, however, that most and being susceptible sheep being able to tolerate 4 many myths and misconceptionsabout tall larkspur poison- times the dose of larkspurthat would be fatal to cattle. ing are not factual. Ranchers with a history of dealing with Horses are intermediate in their susceptibility to larkspur tall larkspur poisoning can be a rich source of information poisoning. Horses are rarely poisoned by larkspur and will leadingto testable research ideas, but some notions should not normally eat the plant unless other forages are unavail- be permanentlydiscarded by the livestock industry so that able. Toxicity studies on the susceptibility of goats, llamas, animal and range managers can deal realistically with tall and alpacas have not been conducted, but it is logical to larkspurpoisoning based on correct and current information. assume the potent alkaloids in larkspur will have similar ef- fects in these species as in cattle and sheep. Literature Cited Myth #8: Bleeding is an effective treatment for lark- Manners, G.D., K.E. Panter, and S.W. Pelletler. 1995. Structure- spur poisoning. of remedies have been advocated for the treatment of activity relationships norditerpeniod alkaloids occurring in Many toxic larkspur(Delphinium) species. J. Nat. Prod. 58:863—869. since the was first larkspur poisoning problem recognized. Marsh, C.D., A.B. Clawson,and H. Marsh. 1916. Larkspur poi- Bleeding of larkspur-poisoned animals by cutting the tail soning of livestock.USDA Bureauof Animal Industry Bull. 365. has been touted as an effective treatment with reme- Pelletler, S.W., P. Kulanthalvel,and J.D. Olsen. 1989. Alkaloids along of dies such as giving atropine, strychnine, potassium Delphiniumbarbeyi. Phytochem.28:1521—1525. per- Pfister, J.A. and GD. Manners. 1991. Mineral manganate, aluminum sulfate, tobacco, and even supplementation whiskey. of cattle grazing larkspur-infested rangeland during drought. J. A great deal is understood about how larkspur kills cattle, Range Manage.44:105—111. RANGELANDS 19(3), June 1997 13

Pfister, J.A. and G.D. Manners. 1995. Effects of carbachol ad- Ralphs, M.H., G.D. Manners, J.A. Ptister, D.R. Gardner, and ministration in cattle grazing tall larkspur-infested range. J. L.F. James. 1997. Toxic alkaloid concentration in tall larkspur Range Manage.48:343—349. species in the western U.S. J. Range Manage.In press. Pfister, J.A., GD. Manners, D.R. Gardner, and M.H. Ralphs. Ternouth, J.H. 1991. The kinetics and requirementsof phospho- 1994. Toxic alkaloid levels in tall larkspur (Delphiniumbarbey,) rus in ruminants. p. 143—152. In: Y.W. Ho, H.K. Wong, N. in western Colorado.J. Range Manage.47:355—358. Abdullah, and Z.A. Tajuddin (eds.), Recent Advances in the Pfister, J.A., M.H. Ralphs, G.D. Manners, D.R. Gardner, K.W. Nutritionof Herbivores,Vinlin Press, Kuala Lumpur. Price, and L.F. James. 1997. Early season grazing of tall lark- spur- (Delphinium spp.) infested rangeland. J. Range Manage. 50:ln press. Authors are professor of Large Animal Internal Medicine,Department Pfister, J.A., M.H. Ralphs, G.D. Manners, K.E. Panter, L.F. of Clinical Sciences,Colorado State Univ., Ft. Collins, Cob.80523, and James, B.L. Stegelmeler, and D.R. Gardner. 1993. Tall lark- rangelandscientist, USDA-ARS Poisonous Plant ResearchLab., Logan, spur poisoning in cattle: current research and recommendations. Ut. 84341. Rangelands15:157—160.