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What is Dogbane Poisoning?

This weed is found in open fields, along roads, beside streams, and grows in pastures in abundance. It is a resilient weed, making it easy to find. Both the green form and the dried leaves are toxic. As little as 30 grams of leaves can be fatal to a horse. Cardiac glycosides within the plant can cause loss of control of the muscles, a weak pulse, and respiratory distress. Your horse may present with symptoms within 12 to 24 hours of his ingesting the weed.

Symptoms can range from mild to severe and the result of the toxicity if left untreated is death. The seeds of the dogbane plant move readily in the wind, making it dangerous and abundant. When cutting hay, it will also be necessary to ensure you are not harvesting dogbane as well. Purchases of hay should be checked; buying hay from a reputable supplier is recommended.

Dogbane is a difficult to contain weed commonly found in North America. The leaves of this plant are toxic when consumed by horses. Fortunately, due to the unpleasant taste, horses do not typically consume dogbane. 

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Symptoms of Dogbane Poisoning in Horses

  • Increase in body temperature
  • Sweating 
  • Cold extremities 
  • Dilated pupils
  • Discolored mouth/nostrils
  • Diarrhea
  • Refusal to eat – related to his mouth becoming sore and creating difficulty eating 
  • Abnormal pulse
  • Staggered gait
  • Bloat – this may be visibly noticeable 
  • Difficulty breathing
  • Weakness

Types

Dogbane is also known as:

  • Bitter root
  • Indian hemp
  • Can easily be mistaken for milkweed as they are in the same family

Causes of Dogbane Poisoning in Horses

  • Your horse may be exposed to the weed anywhere as it is difficult to eliminate from paddocks and pastures
  • Mowing the dogbane plant does not work to eradicate it and herbicide application tends to require multiple sessions
  • The dogbane plant is not naturally appetizing to horses, however if your horse is left without any other options he may consume it
  • The seeds are easily carried around and spread farther, resulting in more plants in more areas
  • When cutting for hay, the dogbane can easily be cut down and added to the hay by accident

Diagnosis of Dogbane Poisoning in Horses

If you suspect your horse has been exposed to dogbane, time is of the essence. It will be important to contact your veterinarian immediately upon having any concerns as treatment options are somewhat time limited. Your veterinarian will want to know if possible, what your horse consumed. Understanding what your horse is exposed to is very important. Proving a sample of what he may have consumed can make diagnosing go easier for your horse and veterinarian. 

Discussing your horse’s current state of health, recent vaccinations and medical history, and his typical diet will be important. If you are giving your horse any supplements, let the veterinarian know. If timing allows your veterinary care giver may do blood tests to evaluate markers indicative of cardiac glycoside toxicity.

Treatment of Dogbane Poisoning in Horses

Elimination of the toxins from the system is important and will be attempted by gastric lavage. This will flush the plant material from the stomach. Activated charcoal may be administered in addition, in order to bind remaining toxins. Further treatment will be of a supportive nature; medication to protect the stomach along with fluids to help the kidneys flush the toxins will be utilized. Horses who have consumed dogbane will need electrolyte and sugar balancing which can be provided with the fluids. Keeping your horse calm and providing a quiet place to rest will be necessary.

Recovery of Dogbane Poisoning in Horses

Follow up will be needed as directed by your veterinarian. A large part of ongoing management for your horse will be to rid the area of dogbane as much as possible and reducing his risk of being exposed to the weed in the future. Understanding the precautions taken by the hay provider if you purchase it to ensure problematic weeds are not put into the hay will also be important.

If you are cutting your own hay, knowing the problematic plants in your area will be necessary as well. Employing the services of a knowledgeable horticulturist is recommended.