buttercups_42066183webGreen pastures make for happy horses and happy horse owners, but do you know what’s really growing in your fields?  Fortunately, when offered adequate forage and feed, most horses preferentially avoid toxic plants.  However, knowing what weeds and grasses are in your pasture can help prevent these unfortunate events or help your veterinarian treat a suspected toxicity.

Dogbane

Dogbane

Several grasses can prove toxic when consumed in large enough quantities. Fescue, a common grass found in pastures, becomes toxic due to a fungi that parasitizes it and produces toxic compounds called ergot alkaloids.  We predominantly see prolonged and complicated gestation in pregnant mares.  Complications range from a lack of milk production to dysmature foals, unhealthy placentas, and, rarely, abortion.  Removing the mare from Fescue for the last few months of pregnancy or treating with Domperidone prior to foaling can minimize these problems. 

With Dallisgrass intoxication, neurologic signs occur such as tremors and convulsions. Treatment includes removing the horse from the pasture. Another common forage, Alsike clover can cause photosensitization (sensitivity to sunlight) and eventually liver damage if consumed for long periods of time.  Other common clovers found in pasture are more harmless.  There most common side effect is a syndrome known as “Slobbers.”  As the name suggests, horses that have eaten more than their fair share of clover will salivate excessively, often with long strings of drool pouring from their mouth.  Removing your horse from the affected pasture will resolve photosensitivity and slobbers, however, liver damage may be irreversible.

Johnson Grass

Johnson Grass

Some weeds you might find in your pasture that can be toxic include dogbane, milkweed, and buttercups.  Dogbane and milkweed have gastrointestinal and cardiac effects, causing symptoms such as colic, diarrhea, and arrhythmias.  Buttercups can cause mild irritation of the mouth and gastrointestinal tract.  In all toxicities, treatment is based on the symptoms the horse is exhibiting.

The list of plants that can be toxic to horses is quite long.  The good news is that if provided adequate hay or good quality pasture, most horses will avoid those plants that are toxic.  Effective pasture management to discourage weed growth and encourage grass for a healthy pasture is the best means of preventing toxicities in horses. For more information, contact your veterinarian or local Virginia Cooperative Extension agent.

Toxic Pasture Grasses:

Meadow Buttercup

Meadow Buttercup

  • Fescue
  • Dallis Grass
  • Alsike Clover
  •  Johnson Grass

Toxic Pasture Weeds:

Milkweed

Milkweed

  • Dogbane
  • Milkweed
  • Buttercups
  • Pokeweed