(Nerium Oleander)

Oleander is seriously poisonous to horses.

Plant Description

Oleander is a shrub that usually grows anywhere from 5 to 25 feet tall. The flowers on this plant are either white, pink, or deep red, and are fairly large.

Geographic Locations

This shrub is found throughout the southwestern and western United States, where it is grown as an ornamental plant. It is also found along roadways and used for windbreaks.

Toxic Plant Components

All parts of this plant are toxic, and it takes surprisingly little to cause severe problems. Death in horses has been reported after eating as few as 30 leaves!

This plant is particularly unpalatable to horses, so they will usually not eat it by choice...usually consumption happens when the leaves contaminate grass clippings given to horses.

Toxicity Cause and Symptoms

It is thought that there are probably many components in the this plant that cause negative reactions, but there are a few that are known for sure.

The first two are oleander and neriine, which are cardiac glycosides (naturally occurring drugs that affect the heart in a positive or negative fashion). These two substances are found in all parts of the plant but are especially concentrated in the sap.

Rosagenin can be found in the bark of this shrub, and it has effects similar to strychnine, including nervousness, difficulty breathing, and death.

Symptoms of poisoning include:

  • Death within 12-24 hours
  • Labored breathing
  • Profuse sweating
  • Abdominal pain or colic-like symptoms
  • Diarrhea (may or may not be bloody)
  • Abnormal heartbeat (either too fast, too slow, or erratic)
  • Poor circulation
  • Tremors or shaking
  • Muscle pain and twitching

Cure and Treatment

Treatment for toxicity is usually symptomatic...the veterinarian will treat various symptoms as they appear.

The veterinarian may choose to administer drugs that relax smooth muscles, or administer laxatives to remove as much of the plant as possible from the system. Unless veterinary treatment is immediate, prognosis for horses suffering from this plant's toxicity is very poor.

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