Toxicity of Extract from Three Larkspur Species (Delphini- um barbeyi, Dmglaucescens, Dm occidentale) Measured by Rat Bioassay - Larkspur poisoning of cattle in North menziesi was poisonous to sheep, but America was reported as early as 1760 Nelson ( 1906) concluded that D. menziesi JOHN D. OLSEN (Miller). About 1900, the United States was not poisonous to sheep. Glover (1906) Highlight: Differences in toxicity among Department of Agriculture and Agricultural reported that at least 18 species vciea of larkspur have been suspect4 but Experiment Stations began to investigate had been found in and that the until now no standard method of comparison and report extensive death losses of cattle four most abundant species were poisonous has been made. A rat bioassay has recently and sheep due to larkspur poisoning in the to livestock. Experimental feeding of been developed and was used to estimate the western United States (Chestnut and larkspur to cattle confirmed field observa- toxicity of an extract from three larkspur Wilcox 1901; Wilcox 1897; Wilcox 1899). tions of symptoms caused by larkspur (Delphinium barbeyi, D. ghzucescens, and D. occidentale). Delphinium barbeyi was the most There was some confusion at that time con- poisoning (Chestnut and Wilcox 190 1; toxic and D. occidentale the least, as measured cerning the relative toxicity of larkspur Marsh et al. 1916) and the report that by this bioassay. species. Irish (1889) fed the tops of 24 toxicity of the seemed to decrease of Delphinium trolliifolium to one during the growing season (Marsh et al. Author is research veterinarian. Poisonous Plant Re- steer and the roots to another and observed 1916). search Laboratory, Agricultural Research Service, Western Region, U.S. Department of Agriculture, no signs of toxicity. He also fed 30 plants of Toxicity studies with guinea pigs and Logan, 84321. “white larkspur” and observed no signs of rabbits have been limited (Beath 1919; Manuscript received December 26, 1976. toxicity. Wilcox (1897) reported that D. Crawford 1907) and no standard method for

JOURNAL OF RANGE MANAGEMENT 30(3), May 1977 237 Table 1. Median lethal dose (LDso) for rats of an alcohol extract from Delphinium barbeyi, D. tested for each species was generally in the glaucescens, and D. occidentale. same stage of growth, the change in toxic throughout the growing season Mean body ’ may not be the same for each species. weight of No. of rats Dose* Mortality LD,04 Confidence The geographical site of growth and the Plant sample rats l (g) injected (mg/g) rate3 (mg/g) interval” seasonal weather conditions may also be a D. barbeyi 297 6 2.93 0 4.5 4.0-5.1 potential factor contributing to a difference 297 6 3.64 0 in toxicity between species. 304 6 4.51 4 The method of extraction used in this 291 6 5.59 5 study was relatively simple and yielded D. glaucescens 255 5 12.33 2 16.2 12.3-21.4 suitably reproducible results for an indi- 226 5 14.43 1 vidual sample of plant material; however, 247 5 16.88 3 extraction of toxic alkaloidal material may 228 5 19.75 4 not have been exactly the same for different D. occidentale 245 5 37.06 1 40.4 37.6-43.5 species. More detailed chemical deter- 250 5 39.29 2 minations will be required to clarify this 257 5 41.65 3 point. 251 5 44.14 4 -~ ’ After 24-hour fast. We will continue to use the bioassay z Dose levels used to determine LD3(, expressed as milligrams of driedplant material equivalent to extract injected method for more detailed study of larkspur subcutaneously, per gram of body weight. toxicity. Potential differences between :( Number of rats that died within 24 hours after injection. years of growth, within a growing season ’ Calculated by method of Weil expressed as milligrams of dried plant material equivalent to extract subcutaneously injected, per gram of body weight. and among species and the effect of envi- .’ Estimation of a confidence interval that will encompass the LDSo 95 times in 100 tests. ronmental factors are being studied. measuring toxicity of larkspur has been weight required to cause toxicosis. Four Literature Cited established. A rat bioassay to estimate the dose levels, increasing in a geometric toxicity of an alcohol extract from larkspur progression, were chosen after preliminary Beath, 0. A. 1919. The chemical examination of tests. The median lethal dose (LDSO) was has recently been developed (Olsen 1977). three species of larkspurs. Univ. of Wyoming This report describes the toxicity to rats calculated from the mortality rate at 24 Agr. Exp. Sta. Bull. 120. 88 p. of extracts from D. barbeyi, D. glau- hours after injection; the method of Weil Chestnut, V. K., and E. V. Wilcox. 1901. cescens, and D. occidentale. The purpose was used (Weil 1952). Stock-poisoning plants of Montana. U.S. Dep. of the study was to investigate whether Agr. Div. Bot. Bull. 26:65-80. Results and Discussion differences in toxicity between larkspur Crawford, A. C. 1907. The larkspurs as poison- Clinical signs of toxicosis could be species from different locales could be ous plants. U.S. Dep. Agr., Bur. Plant Ind. observed 1.5 hours after injection, and Bull. 111:5-12. measured. most animals died between 1.5 and 18 Glover, G. H. 1906. Larkspur and other poison- hours after injection. ous plants. Colorado Agr. Exp. Sta. Bull. 113. Methods The LDso for extracts from each larkspur 24 p. The above-ground parts of the three species has been listed in Table 1. The LDsO Irish, P. H. 1889. Plants poisonous to stock. species of larkspur were collected in 1973 was significantly different for each species. Oregon Exp. Sta. Bull. 3:25. Marsh, C. D., A. B. Clawson, and H. Marsh. during the early flower bud stage, i.e., D. barbeyi was the most toxic and D. 1916. Larkspur poisoning in livestock. U.S. small, unopened buds were visible on some occidentale the least. The confidence Dep. Agr. Bull. 365. 91 p. plants. Delphinium barbeyi was collected interval was much narrower for D. barbeyi Miller, P. 1760. The Gardener’s Dictionary. at an elevation of 3,109 m at the head of than for the others. This narrow confidence Vol. 2. London. (Cited by Marsh et al. U.S. Manti Canyon in central Utah; Delphinium interval was a result, in part, of the fact that Dep. Agr. Bull. 365, 1916.) claucescens was collected at an elevation of the death loss at the intermediate doses Olsen, J. D. 1977. A rat bioassay for estimating 2,438 m on the border of Idaho and (mortality rate in Table 1) was sharply toxicity of plant material from larkspur (Del- Montana north of Dubois, Ida.; and different for D. barbeyi. phinium sp.) Amer. J. Vet. Res. 38:277-279. Pelletier, S. W., and L. H. Keith. 1970. Diter- Delphinium occidentale was collected at an The difference in toxicity between pene alkaloids from Aconitum, Delphinium, elevation of 1,829 m east of Ashton, Ida. species, as measured, could result from and Garryu species. Edited by R. H. F. Extracts of air-dried, ground plant material several factors. Manske, The Alkaloids, Vol. XII. Academic were tested for toxicity to rats as previously A number of potentially toxic alkaloids Press, New York. p. l-206. described (Olsen 1977). An alcohol extract have been isolated from Delphinium sp. Nelson, S. B. 1906. Feeding wild plants to was made, evaporated to dryness, and (Pelletier and Keith 1970). The type of sheep. Washington Agr. Exp. Sta. Bull. 73: reconstituted in saline solution. Rats of major , or the chemical form in 46-5 1. either sex were individually identified, which it exists, may vary among these Weil, C. S. 1952. Tables for convenient calcula- weighed, and caged in groups of six. The species. Also, the absolute concentration of tion of median-effective dose (LD,, or ED,,) undiluted saline extract was subcutaneous- alkaloid present in these Delphinium and instructions in their use. Biometrics 8: 249-263. ly injected. At each site, 1 ml or less was species may be different, or the concen- Wilcox, E. V. 1897. Larkspur poisoning of injected. The dose for each rat was tration ratio of the various alkaloids present sheep. Mont. Agr. Exp. Sta. Bull. 15:37-51. calculated on the basis of the amount of may vary. Wilcox, E. V. 1899. Cattle poisoning by the tall saline extract injected (dose expressed as Another factor is the stage of growth of larkspur. Montana Agr. Exp. Sta. Bull. 22: mg of dry plant extracted) per gram of body the plant. Even though the plant material 45-47.

238 JOURNAL OF RANGE MANAGEMENT 30(3), May 1977