Common Name
Blue Flax, common flax.
Botanic Name
Linum perenne (an introduced species that is common and invasive) Linum lewisii (native species). Linum usitatissimum (introduced species)
Plant Family
Linaceae (Flax family)
Widely distributed from the plains to higher mountain meadows. Common along roadsides.
Throughout North America
Animals Affected
Cattle, sheep, goats. Ruminants are more susceptible to cyanide poisoning than horses because rumen microorganisms rapidly hyrolyse the cyanogenic glycosides to release free hydrogen cyanide.
Blue-flax (Linum usitatissimum)
Toxic Principle
Cyanogenic glycoside linamarin which is hydrolysed in the rumen by the plant enzyme linamarase, and rumen microorganisms to produce hydrogen cyanide (HCN). Like other cyanogenic plants the glycoside is found in all parts of the plant. Cyanide blocks the action of cytochrome oxidase that prevents hemoglobin from releasing oxygen to the tissues. Death results rapidly from anoxia. Uncooked linseed oil and linseed cake is also toxic. The presence of cyanides, sulfocyanates, thiocyanates may also cause hyperplastic goiter if eaten in quantity. Blue flax may also accumulate nitrates.
Annual or perennials hairless plants with slender stems and alternate fine leaves. Light blue 5-petaled flowers drop their petals by midday. New flowers open daily. Seeds are flat and black. There are numerous species of flax the more common being L. perenne var.lewisii L. usitatissimum, an introduced species can become locally invasive. Yellow flax is L. rigidum.
Without stressing the animal, sodium thiosulfate and sodium nitrite should be given intravenously. A mixture of 1ml 20% sodium nitrite and 3ml of 20% sodium thiosulfate should be prepared and given at the rate of 4 ml of the mixture per 100lbs body weight. Sodium thiosulfate should be given orally via stomach using 30gm dissolved in a gallon of water.
Cardiovascular system
Sudden death. Initially animals show difficulty in breathing. Open mouth breathing is common as the animal becomes oxygen deprived. Excessive salivation, nervousness and weakness precede death. Mucous membranes appear pink and redder than normal. Venous blood is cherry red in color. Stressing the animal rapidly leads to collapse and death.
Respiratory System
Severe respiratory difficulty followed shortly by death.
Sudden death with supporting evidence of cherry-red venous blood and absence of other diseases. Rumen contents or plant material can be tested for cyanide using the sodium picrate test. Commerical test kits for cyanide are available.
Special Notes
Blue flax is unlikely to be a problem unless cattle and sheep eat large quantities of the plant. Horses are rarely if ever affected by plants containing cyanogenic glycosides as their digestive system does not readily convert the glycodsides to free cyanide. Uncooked linseed cake and linseed oil may contain toxic levels of cyanogenic glycosides. Cooking/heating the linseed meal after the oil is extracted reduces significantly the cyanogenic glycosides. Reference: 1. Oomah BD, Mazza G, Kenaschuk EO. Cyanogenic compounds in flaxseed. J Agric Food Chem. 1995, 208:6-12. Moore J. Prussic acid poisoning from the use of linseed cake.. Vet J 1924. 80:33-34
Blue flax (Linum lewisii)