Details

Common Name
Low larkspur, foot-hills larkspur and plains larkspur
Botanic Name
Delphinium nuttallianum, D. andersonii, D. bicolor (low larkspur). Delphinium geyeri (Foot-hills larkspur), D. virescens (Plains larkspur)
Plant Family
Ranunculaceae
Habitat
Open woodlands and meadows, prairies, and foot hills
Animals Affected
Cattle.
Delphimium nuttallianum - Low larkspur
Toxic Principle
Diterpenoid alkaloids - methyllycaconitine and nudicauline amongst others. The alkaloids act principally at the neuromuscular junction blocking muscle-type nicotinic acetylcholine receptors which prevents the neurotransmitter acetylcholine from binding to and activating the receptor. Due to this receptor blockade, cattle develop muscle weakness, tachycardia, failure of voluntary muscular coordination, sternal recumbency followed by lateral recumbency, bloating, respiratory depression, and death. Foothills larkspur appears to be most toxic in the preflowering stage. There is however considerable variation in the toxicity of the plants from year to year.
Description
Erect, weak-stemmed perennials, up to 18 inches tall, with hairy upper leaves and stems. Flowers are produced on a short racemes, and are characteristically deep blue-purple, with typical spur.
Gastrointestinal
Bloat and regurgitation of rumen contents.
Musculoskeletal
Weakness, muscle tremors, and eventual collapse of the animal especially if stressed.
Treatment
Avoid stressing the affected animals. Gently herd the cattle away from the larkspur area. Where possible give physostigmine intravenously (0.04mg/kg body weight) with as little stress as possible. Neostigmine sulfate administered intravenously or intramuscularly at a dose of 0.02 – 0.04 mg/kg can also be used for treating larkspur poisoned cattle. Keep the animal on its sternum to reduce bloating, and if necessary treat the bloat by passing a stomach tube, or by trocarizing the rumen to relieve the pressure.
Respiratory System
Death due to respiratory paralysis and bloat.
Nervous System
Muscular paralysis due to the neurotoxic alkaloids binding to acetylcholine receptor sites causing muscle paralysis.
Diagnosis
A diagnosis of larkspur poisoning can be made from associating the typical clinical signs with the cattle having access to and having eaten the larkspur.
Special Notes
The low and foothills species of larkspur emerge early in the spring before the grasses mature and consequently cattle are prone to eating the succulent green larkspur plants. Herbicide control of low larkspur. 2,4-D and picloram have been shown to be effective at controlling low and plains larkspur. Reference 1.Green BT et al: Effects of larkspur (Delphinium barbeyi) on heart rate and electrically evoked electromyographic response of the external anal sphincter in cattle. Am J of Vet Research 2009, 70: 539-546. 2.Panter KE et al: Larkspur poisoning: toxicology and alkaloid structure–activity relationships. Biochemical Systematics and Ecology 2002, 30:113-128. 3. Pfister JA, Gardner DR, Stegelmeier BL, et al. Catastrophic cattle loss to low larkspur (Delphinium nuttallianum) in Idaho.Vet Hum Toxicol 2003;45:137-9. 4. Pfister JA, Gardner DR, Panter KE, Consumption of low larkspur (Delphinium nuttallianum) by grazing sheep. Rangeland Ecol Manage 2010;63:263-266.
Low larkspur flower
Delphinium geyeri - leaves preflowering
Delphinium geyeri - Foothills larkspur
Low larkspur flowers
Delphinium virescens