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Poisonous Plant Alert
the Equine Research Centre, Guelph, Ontario


Partnerships and collaboration are key elements for success in the 21st century. This brochure was produced by the Horse Council of British Columbia. It is presented here as a part of ongoing cooperative ventures between the Horse Council of BC and the Equine Research Centre. A special thank you to the Horse Council of BC and their executive director, Laurel Wood.
Andrew Clarke

Toxic Plants: Is your horse safe?
Is your horse's pasture free from toxic plants? Are you sure? It is important for horse owners to be aware of potentially fatal plants that could be present in your pastures. This brochure provides you with some simple ways to help avoid pasture poisoning, lists some resources available to help identify plants and offers suggestions in case of suspected poisoning.

How to Avoid Poisoning: Preventative Medicine
The single most effective thing you can do to ensure that your horses will be unlikely to eat poisonous plants is to ensure that they have access, day and night, to good pasture and/or good hay. Sensible horse management can prevent almost all cases. Additional suggestions include:

  • Provide adequate forage - normally, horses will only eat toxic flora if nothing else is available. Well-nourished horses are less likely to be tempted to try unfamiliar vegetation.
  • Recognize boredom - bored horses may chew on plants, bark, leaves. Regular exercise helps ward off boredom.
  • Check out new venues - scout new pastures for dangerous vegetation and make careful note of what your horse is grazing on. Ensure horses cannot access ornamental shrubbery, plants or flowers. Remove shrubs and trees from pastures - replace with a shed for shelter.
  • Practice proper pasture management. A rule of thumb is one acre of good pasture per horse. Mow pastures two or three times during the growing season and regularly drag pastures to break up manure piles. If irrigated, keep irrigating throughout the growing season and fertilize regularly. Keep pruned branches, cuttings, leaves and discarded garden plants away from pastures. Remove broken branches promptly after storms.
  • Be watchful - especially at the beginning of the growing season when weeds sprout faster than grass and the end of the season when grazed areas are more barren, leaving horses few forage options. Learn to recognize the symptoms of possible poisoning.
  • Learn to identify poisonous and toxic plants in your geographic area. Sometimes poisoning works slowly from gradual intake over days or weeks.

Other sources of potential poisonings: Feed (hay, etc.) and water sources
Horse owners should recognize that poisoning can result from contact with several potential sources, other than ingestion of toxic plants.

  • Don't feed lawn clippings or garden refuse. Discard these or compost in an area away from horses.
  • Don't allow horses to graze where herbicides have been used.
  • Don't allow access to water with coloured or oily scum on the surface or that smells foul.
  • Don't feed cow rations (which may contain cottonseed meal).
  • Don't feed mouldy grain or pellets.
  • Check your hay carefully - don't assume it is free of toxic plants.

What to Do in Case of Poisoning or Suspected Poisoning:
If you suspect your horse has ingested some type of poison or contaminated feed or water, it is important to act quickly. Be armed with as much information as you can provide regarding the type of poisoning when you call your health care professional.

  • Contact your veterinarian or NAPCC (the National Animal Poison Control Centre)
  • Remove other horses from the pasture even though they may not exhibit symptoms.
  • Try to identify the plant ingested. The NAPCC suggests that you be able to respond to certain questions. (see NAPCC section on the Resource List).

Be aware potentially toxic plants that may exist in your region and take precautions to avoid possible poisoning. Sensible horse management can prevent almost all poisoning cases.

Resource List

Help Line
National Animal Poison Control Centre (NAPCC) 1-800-548-2423

Calls are taken 24 hours a day. The cost is $30.00 US per case, including unlimited follow up calls in critical cases and a consultation with the owner's veterinarian. A credit card is necessary and be prepared to answer the following questions:

  • What plant do you believe the horse was exposed to?
  • How much of the plant do you think the horse are and over what period of time?
  • How many horses are involved?
  • Each horse's breed, age, sex and weight?

"Weeding out poisonous plants, keeping your pastures and horses safe" by Gordon DeWolf Jr., PhD (International Arabian Horse Magazine, April/May 1995)

"Providing optimal pasture" by Jimmy C. Henning, University of Kentucky (Mohill Farm Management, Equine Research Centre, Guelph, November 1994)

"Poisonous plants: A survival guide" by Jack Moore (Equus 212, June 1995)

"Poisonous Weeds" by Theresa Rondeau Vuk (Mohill Farm Management, Equine Research Centre, Guelph, November 1994)

"Has my horse been poisoned?" by Jack Moore (Equus 212, Back page, June 1995)

"Poisoned in the paddock: by Leslie J. Kelley (Equus 199, Case Report, May 1994)

"Odd behaviour and liver disease" (Equus 168, Medical Front, October 1991)

"Poisonous plant alert" (Equus 152, Hands On, June 1990)

"Plant poisoning: Are your horses at risk?" by Emily Kilby (Equus 119, September 1987)

"Poisonous plants garden cultivates awareness to save lives" (Equus 102, April 1986)

"The sky is blue, the grass is green, the horse is dead" (Equus 21, July 1979)

BC Ministry of Agriculture brochures:
"Alsike clover toxicity in horses" Forage Info Series
"Tansy ragwort in British Columbia"

"Mohill Farm Management" from the Equine Research Centre, Guelph, ON., November 1994.

"Poisonous Plants of the Central United States" by H.A. Stephens (Lawrence, Kansan: University Press of Kansas, 1980, 1984)

"Poisonous Plants of the Southern United States" by Anon. (Athens Georgia: Georgia Cooperative Extension Service, 1980)

"Plants Poisonous to Livestock in the Western States" by L.F. Janes, et al (USDA Agricultural Research Service, Agriculture Information Bulletin #415, 1988)

"North American Wildlife, An Illustrated Guide to 2,000 Plants and Animals" (Reader's Digest, Pleasantville, NY, 1982)

"Natural Toxicants in Feeds and Poisonous Plants" by P.R. Cheeke and L.R. Schull (AVI/Van Nostrand Reinhold Co., NY, 1987)

"Natural Poisons in Horses" (National Animal Poison Control Centre, University of Illinois College of Veterinary Medicine, Urbana, IL)

5746B 176A STREET
(604) 576-2722
FAX (604) 576-0401

The Equine Research Centre, Guelph, Ontario This article was kindly contributed by the Equine Research Centre, Guelph, Ontario. For further information please click here

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© Equine Research Centre, 1996- 2000

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