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What is Robinia Species Poisoning?

Of the genus Robinia is Robinia pseudoacacia L., also known as black locust. A member of the Fabaceae family (also known as the Bean family), the black locust is a tree that produces long, white flowers that are clustered in a similar fashion to grapes for about ten days in the spring. The tree can grow to between 50 and 70 feet and in addition to flowers will produce a fruit that is 5-10 centimeters long. The fruit is reddish brown, becoming black over the course of the winter.

There are several species of locust trees found in the eastern part of the United States and they are also used for landscaping. The black locust is a hardy tree that grows in a variety of environments and soil conditions. 

While this plant is noted in some textbooks as an emergency food (inner bark of the tree or flowers fried) extreme caution should be taken when it comes to ingesting the black locust.

The genus Robinia includes the black locust, which contains two toxic compounds, the ingestion of which can lead to a variety of symptoms in horses.

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Symptoms of Robinia Species Poisoning in Horses

Should your horse experience Robinia toxicity, he may show the following symptoms:

  • Nausea
  • Diarrhea (with or without the presence of blood)
  • Lack of appetite
  • Swelling and irritation of the lining that surrounds the digestive organs
  • Dilated pupils
  • Yellowish pigment to the membranes
  • Cool extremities
  • Venous congestion
  • Kidney failure
  • Weakness
  • Shortness of breath
  • Weak pulse
  • Congestion in the veins
  • Higher than usual heart rate
  • Depression

Symptoms typically present themselves within hours of ingestion.

Types

Other species of Robinia include: R. hispida L. and R. viscosa Vent. These have pink flowers and seed pods that have hairs that are stiff and spread.

Causes of Robinia Species Poisoning in Horses

It is thought that there are two compounds in the black locust that are responsible for toxicity. The first is a phototoxin called robin; its toxic principles are similar to those in the castor bean and is present in the bark, seeds and leaves of the black locust. The second is robitin, which is a glycoside. Two other compounds, acetin and robinetin are present however it is not clear whether these substances are involved in toxicity. Consuming 0.04% of their body weight can be toxic to your horse. The plant is poisonous whether fresh or dry.

Diagnosis of Robinia Species Poisoning in Horses

Should you notice your horse ingesting a portion of the black locust, or notice concerning symptoms, it is important that you seek medical attention to determine whether he has experienced toxicity. Bring a sample of the plant that you know or suspect that he ingested, as this will be helpful to your veterinarian as he attempts to diagnose your horse.

Your veterinarian will ask you for information regarding the symptoms that you have noticed in your horse, when you first noticed them and if you have observed any changes. In addition to conducting a physical examination, your veterinarian may request laboratory work be performed. This may include blood work (a complete blood count), a chemistry panel and a urinalysis. Should cardiovascular difficulties be noticed during the examination, your veterinarian may monitor your horse’s heart.

Treatment of Robinia Species Poisoning in Horses

Treatment for robinia species poisoning is supportive and will be dependent upon the symptoms that your horse is experiencing. Intravenous fluids are often administered as they will help to flush out the toxin as well as ensure that your horse remains hydrated. Should your horse’s breathing be impacted, oxygen may be administered to help with his breathing. Medication may be given for any other symptoms that are experienced, as well as electrolytes to balance abnormalities in your horse’s system that may have resulted due to the toxic effects.

Recovery of Robinia Species Poisoning in Horses

How quickly your horse receives treatment after consuming black locust, along with how much he actually ingested, will impact his ability to recover. Should a significant amount of a plant of the robinia species be ingested and a long period of time elapse before treatment, renal failure can result. 

You will want to work closely with your veterinarian regarding the treatment of your horse after experiencing robinia species poisoning. Follow up appointments may be necessary in order to check on his progress. It is important that you examine the areas where your horse has access to ensure that there are no poisonous plants that may be consumed and lead to poisoning in your horse.