Field horsetail
General poisoning notes:
Field horsetail (Equisetum arvense) is a native plant growing across Canada. This plant contains thiaminase which causes thiamine deficiency in horses. Ruminants are not generally affected by problems of thiamine deficiency because it is made in the rumen. However, some cattle were reported to have symptoms. In Canada, horses have been poisoned by ingesting field horsetail (Henderson et al. 1952, Cheeke and Schull 1985).
Nomenclature:
Scientific Name: Equisetum arvense L.
Vernacular name(s): field horsetail
Scientific family name: Equisetaceae
Vernacular family name: horsetail
Equisetum arvense L.
Geographic Information
Alberta, British Columbia, Labrador, Manitoba, New Brunswick, Newfoundland, Northwest Territories, Nova Scotia, Ontario, Prince Edward Island, Quebec, Saskatchewan, Yukon Territory
Notes on Poisonous plant parts:
The horsetails have separate fertile and sterile fronds. Field horsetail has a fertile frond that is flesh-colored and appears before the green sterile frond.
Toxic parts:
Leaves, stems
Notes on Toxic plant chemicals:
Thiaminase is an enzyme that splits thiamine, a B vitamin, making it inactive. Thiamine is involved in decarboxylation reactions in animal bodies. Deficiency of thiamine leads to accumulation of pyruvate in the blood, with a resulting impairment in energy metabolism and cellular shortage of ATP. Hay that contains horsetail at a level of 20% or more may produce symptoms of thiamine deficiency in horses in 2-5 weeks (Cheeke and Schull 1985).
Toxic plant chemicals:
Thiaminase
Animals/Human Poisoning:
Note: When an animal is listed without additional information, the literature (as of 1993) contained no detailed explanation.
