Introduction

Livestock can be poisoned or injured by certain plants while grazing or fed in stored feed. The OMAFRA fact sheet "Poisoning of Livestock by Plants", Agdex 130/643, reviews the types of poisoning which can occur and the effects on animal health and production.

Many common weeds in Ontario can poison livestock. This fact sheet identifies these weeds and describes the symptoms of poisoning. Because some poisons act very fast (as with the hemlocks) by the time the symptoms are evident, the chances of saving the animal are very slight. It is, therefore, important to learn to recognize these weeds beforehand and prevent poisoning from occurring. Most of these weeds can be controlled chemically or mechanically. In some cases, it may be more practical to simply fence off infested areas so that the animals do not have access to particularly hazardous weeds.

It should be noted that most of these weeds are unpalatable and animals will usually not graze them if given the choice. One of the most important steps in preventing animal suffering or loss is good pasture management. Keeping the desirable forage species producing throughout the grazing season, reduces the possibility of animals grazing poisonous weeds.

If symptoms of poisoning should occur, it is recommended that you call your veterinarian as soon as possible.

Common weeds poisonous to grazing livestock

Poison Hemlockfootnote 1 (Conium maculatum)

Poison Hemlock
Where generally located
  • waste areas
  • road sides
  • dry ditches
Livestock affected
  • cattle
  • horses
  • sheep
  • goats
Symptoms
  • death may occur within 15 minutes
  • frothing at the mouth
  • uneasiness
  • pain
  • dilated pupils
  • clamping of jaws
  • grating of teeth
  • vomiting
  • weak, rapid pulse
  • diarrhea
  • bloating
  • convulsions
  • respiratory failure
  • death

Water Hemlockfootnote 1 (Cicuta maculata)

Water Hemlock
Where generally located
  • wet pastures
  • stream banks
  • pond edges
  • lake edges
  • wet ditches
  • edges of wet woods
Livestock affected
  • cattle
  • horses
  • sheep
  • goats
Symptoms
  • death may occur within 15 minutes
  • frothing at the mouth
  • uneasiness
  • pain
  • dilated pupils
  • clamping of jaws
  • grating of teeth
  • vomiting
  • weak, rapid pulse
  • diarrhea
  • bloating
  • convulsions
  • respiratory failure
  • death

Bracken Fernfootnote 1 (Pteridium aquilinum)

Bracken Fern
Where generally located
  • open fields
  • woodlands
  • low ground
  • dry, rocky soil
Livestock affected
  • horses
  • cattle
  • sheep
Symptoms
  • Horses:
    • symptoms are slow to develop
    • loss of flesh
    • jaundice
    • loss of appetite
    • weakness
    • staggering gait
    • excitability
    • paralysis
  • Cattle and sheep:
    • symptoms are slow to develop
    • high fever
    • labored breathing
    • drooling
    • hemorrhaging from nostrils
    • blood in urine and feces
    • convulsions

Marsh Arrow-Grass (Triglochin palustris)

Marsh Arrow-Grass
Where generally located
  • marshes
  • alkaline soils
Livestock affected
  • cattle
  • sheep
Symptoms
  • symptoms appear rapidly
  • rapid, difficult breathing
  • almond odor to breath
  • animals go down with head turned to one side

Horsetailfootnote 1 (Equisetum arvense)

Horsetail
Where generally located
  • poorly drained soils
  • low, sandy, acid soils
  • cultivated fields
  • roadsides
  • waste areas
  • woods
Livestock affected
  • horses
  • cattle
  • sheep
Symptoms
  • symptoms are slow to develop
  • jaundice
  • loss of appetite
  • weakness
  • staggering gait
  • excitability
  • paralysis

Pokeweedfootnote 1 (Phytolacca americana)

Pokeweed
Where generally located
  • (southern Ontario only)
  • waste areas
  • meadows
  • edges of woods
Livestock affected
  • cattle
Symptoms
  • symptoms occur two or more hours after plants are eaten
  • retching spasms
  • vomiting
  • purging
  • convulsions

Marsh Marigoldfootnote 1 (Caltha palustris)

Marsh Marigold
Where generally located
  • wet areas
Livestock affected
  • cattle
Symptoms
  • acute inflammation of the gastro-intestinal tract
  • vomiting
  • colic
  • bloody urine
  • diarrhea
  • twitching of the eyelids
  • weak pulse
  • loud breathing
  • reduce milk production
  • tainted milk red in colour and bitter tasting

Tall Buttercupfootnote 1 (Ranunculus acris)

Tall Buttercup
Where generally located
  • pastures
  • meadows
  • roadsides
Livestock affected
  • cattle
  • horses
  • sheep
  • goats
Symptoms
  • inflammation and blisters where plant juice touched the animal
  • mouth blisters cause drooling and loss of appetite
  • other symptoms similar to those for marsh marigold

Wild Cherries Black (Prunus virginiana) 

Wild cherries black (choke and pin)
Left (#) = Choke. Right (##) = Pin.
Where generally located
  • fence rows
  • open woods
Livestock affected
  • cattle
Symptoms
  • same as with march arrow-grass poisoning

Lupine (Lupinus polyphyllus)

Lupine
Where generally located
  • pastures
  • meadows
  • roadsides
  • waste areas
Livestock affected
  • sheep
  • cattle
  • horses
Symptoms
  • nervousness
  • labored breathing
  • convulsions
  • frothing at the mouth
  • frenzy
  • aimless running about

Saint-John's Wortfootnote 1 (Hypericum perforatum)

Saint John's Wort
Where generally located
  • roadsides
  • pastures
Livestock affected
  • horses
  • cattle
Symptoms
  • photo-sensitivity
  • inflammation of the unpigmented portion of the skin
  • affected area becomes sore and reddened and may peel
  • tongue and mouth may be affected

Nightshadefootnote 1 (Solanum sp.) 

Nightshade (Eastern Black and Black Hairy Climbing)
Left (##) = Black Hairy Climbing. Right (#) = Eastern Black.
Where generally located
  • open dry woods
  • cultivated fields
  • pastures
  • fence rows
  • waste areas
  • farm yards
Livestock affected
  • cattle
  • horses
  • sheep
  • goats
Symptoms
  • abdominal pain
  • stupidity
  • dilation of pupils
  • loss of appetite
  • diarrhea
  • loss of muscular coordination
  • unconscious
  • death

Jimsonweed (Datura stramonium)

Jimsonweed
Where generally located
  • cultivated fields
  • farm yards
Livestock affected
  • cattle
  • horses
  • sheep
  • goats
Symptoms
  • dilation of the pupils
  • impaired vision
  • fast, weak pulse
  • nausea
  • loss of muscular coordination
  • violent, aggressive behaviours
  • trembling
  • milk is tainted

Milkweedfootnote 1 (Asclepias sp.) 

Milkweed (Whorled and Common)
Left (##) = Common. Right (#) = Whorled. 
Where generally located
  • dry, open areas
  • pastures
  • around woods
  • roadsides
  • waste areas
  • cultivated fields
Livestock affected
  • cattle
  • sheep
  • horses
Symptoms
  • Cattle and sheep:
    • loss of appetite
    • constipation
    • drooling
    • excitable
    • difficult breathing
    • rapid, weak pulse
    • convulsions
    • death
  • Horses:
    • persistent colic

Cocklefootnote 1 (Saponaria officinalis) 

Cockle (Purple and Cow Cockle Bouncingbet)
Left (#) = Purple Cockle. Right (##) = Cow Cockle Bouncingbet.
Where generally located
  • pastures
  • cultivated fields
  • roadsides
  • waste areas
Livestock affected
  • horses
  • cattle
Symptoms
  • restlessness
  • grinding of teeth
  • drooling
  • colic
  • diarrhea
  • rapid breathing
  • weak pulse
  • coma
  • death

Laurel (Kalmia sp.) 
Sheep Pale or Bog

Laurel (Sheep Pale or Bog)
Where generally located
  • bogs
  • wet evergreen woods
Livestock affected
  • cattle
  • sheep
  • goats
Symptoms
  • drooling
  • watery eyes
  • runny nose
  • vomiting
  • complete or partial blindness
  • drowsiness
  • convulsions
  • paralysis

Tansy Ragwortfootnote 1 (Senecio sp.)

Tansy Ragwort
Where generally located
  • pastures
  • hayfields
  • waste areas
  • roadsides
Livestock affected
  • horses
  • cattle
Symptoms
  • nervousness
  • chills
  • pale mucous membranes
  • loss of coat lustre
  • strong, rapid pulse
  • high temperature
  • staggering gait
  • weakness
  • death

Spurgefootnote 1 (Euphorbia sp.) 
Cypress Leafy

Spurge (Cypress Leafy)
Where generally located
  • cultivated fields
  • waste areas
  • roadsides
Livestock affected
  • horses
  • goats
  • cattle
  • sheep (leafy is non toxic to sheep)
Symptoms
  • Contact with sap:
    • causes inflammation of skin
  • Eating causes:
    • diarrhea
    • vomiting
    • swelling around mouth and eyes
    • abdominal pains
    • muscle tremors
    • sweating
    • tainted milk has reddish colour, bitter taste

White Snakeroot (Eupatorium rugosum)

White snakeroot
Where generally located
  • wooded areas
  • persists after woods are thinned out
  • stream banks
Livestock affected
  • horses
  • cattle
  • goats
  • sheep
Symptoms
  • Horses, cattle and goats:
    • depression
    • inactivity
    • arched body
    • hind feet place close together
    • excessive salivation
    • nasal discharge
    • nausea
    • rapid, labored breathing
  • Sheep:
    • above, except sheep stand with legs apart

Cockleburfootnote 1 (Xanthium chinensis)

Cocklebur
Where generally located
  • cultivated fields
  • stream banks
  • beaches
  • farm yards
Livestock affected
  • horses
  • cattle
  • sheep
Symptoms
  • symptoms appear within a few hours
  • weakness
  • unsteady gait
  • twisting of neck muscles
  • depression
  • nausea
  • vomiting
  • labored breathing
  • rapid, weak pulse
  • death

Sneezeweed (Helenium automnale)

Sneezeweed
Where generally located
  • wet areas
  • roadside ditches
  • stream banks
Livestock affected
  • cattle
  • horses
  • sheep
Symptoms
  • symptoms are slow to develop
  • loss of vigor
  • loss of flesh
  • rapid pulse
  • labored breathing
  • loss of muscular control
  • drooling
  • high temperature
  • dizziness
  • spasms
  • convulsions

Squirrel Corn/Dutchman's Breeches
(Dicentra sp.)

Squirrel Corn and Dutcheman's Breeches
Left (#) = Squirrel Corn. Right (##) = Dutchman's Breeches.
Where generally located
  • wooded areas (maple woods)
Livestock affected
  • cattle
Symptoms
  • symptoms develop 48 hours after plants are eaten
  • trembling
  • frothing at the mouth
  • vomiting
  • diarrhea
  • labored breathing
  • convulsions