This section is from the book "A Guide To The Poisonous Plants And Weed Seeds Of Canada And The Northern United States", by Robert Boyd Thomson, H. B. Sifton. Also available from Amazon: A guide to the poisonous plants and weed seeds of Canada and the northern United States.
The poisonous effects of European Larkspurs have been known for centuries. One species, D. Staphisagria L., called Stavesacre, was used as a poison for lice. Many species are common in the west of Canada and the United States, and have occasioned great losses among cattle on the ranges. Marsh and Clawson place them next to the "loco" weeds in the number of animals killed, and Glover, in 1906, estimated the annual monetary loss, in Colorado alone, at $40,000. All parts of the plants are poisonous, the seeds most of all. Leaves and roots are most harmful in early spring. The effects gradually decrease until after flowering, when practically all of the alkaloids seem to collect in the seed and the rest of the plant becomes harmless.
Stockmen have blamed the Larkspur for a large part of their losses in both cattle and sheep, and until a few years ago this opinion was entertained even by those who should have scientifically investigated the matter. In 1916, however, Marsh and Clawson published an account of experimental work which led them to believe that sheep can withstand the poison, probably on account of its prompt excretion by their kidneys. In repeated instances sheep were fed large quantities of the plants and in no case was any injury produced. They found horses to be susceptible to the poison, though they do not voluntarily eat enough to harm them. In the case of cattle the results are quite different, the plant proving very poisonous, especially in the early spring when the cattle eat the young growth greedily. Poisoning also occurs at other times, when animals are changed to a new range, or in autumn when other plants are covered by snow and cattle are sometimes tempted to feed on the projecting seed capsules of the taller forms.
Fig. 9. - Larkspur - Delphinium sp.
The principal poisons contained are two alkaloids, del-phinin and staphisagrin, of which the former is the more harmful. The first symptoms noticed are a stiffness of the limbs, and a somewhat straddling gait. Respiration is slow at first, then rapid. In one heifer it increased to 128 per minute. The appetite is not much impaired and the brain functions normally, though the sick animals are easily frightened. There is constipation and abdominal pain, and in the later stages nausea and vomiting, from which death often results by suffocation. Bloating is sometimes present, but is not common before death, although taking place rapidly afterward. A quivering of the muscles and weakness is prominent, the legs crumpling up under the animal. Congestion of heart, lungs and central nervous system and inflammation especially of the rumen, the oesophagus and the pyloric end of the fourth stomach are post-mortem indications. The alkaloid evidently acts as a local irritant and a nerve depressant. If recovery takes place it is usually very rapid. The treatment indicated is (1) magnesium sulphate to overcome the constipation, (2) a chemical antidote for the poison remaining in the stomach, and (3) injections of a physiological antidote for that which has been absorbed. Chesnut and Wilcox recommend a 1% solution of potassium permanganate and aluminium sulphate as a chemical antidote, one quart being enough for three to five cows, or seven to ten horses; and injections of one-half to one grain of atropin. Marsh and Clawson report poor results from this treatment and recommend the use of Epsom salts and injections of a combination of physostigmin salicylate, pilocarpin hydrochloride and strychnin sulphate, supplemented by hypodermics of dilute alcohol where weakness is very pronounced. All excitement should be avoided and the animal kept with its head higher than the rest of the body. Where bloating occurs, it should be relieved by paunch-ing.
As noted above, many species of Larkspur are found in Canada and the United States, but a detailed classification is unnecessary. All have leaves with deep palmate lobes and flowers in a loose elongated terminal cluster. The flowers vary from bright blue to pale violet and yellow, both sepals and petals being coloured. Each is provided with a long spur. The glistening black seeds are contained in erect, horned capsules. The species are divided into two groups. The low Larkspurs grow from six inches to three feet tall and the foliage dies and dries up at seeding time. The tall species are three to six feet high, and retain their leaves for a longer period.