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What is Yellow Bristle Grass Poisoning?

Yellow bristle grass can be found throughout the world and is considered a weed in many regions.  It produces bristles or awns that can become lodged in your horse’s mouth if he ingests it.  This can lead to discomfort, severe pain, and even ulcers.  It can affect his appetite and water intake and therefore can lead to other issues.  Diagnosis is usually by physical exam alone and treatment is in response to his symptoms.  If you are able to prevent further ingestion and treat his symptoms, prognosis of a full recovery is good.

Yellow bristle grass should not be ingested by your horse; it can lead to mouth and stomach ulcers.  As a result of the ingestion, your horse can become anorexic and should be seen by a veterinarian as soon as possible.

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Symptoms of Yellow Bristle Grass Poisoning in Horses

Symptoms of yellow bristle grass poisoning can include:

  • Stomach ulcers
  • Mouth ulcers
  • Mouth irritation
  • Tongue irritation
  • Lip irritation
  • Lack of appetite
  • Anorexia 
  • Decreased drinking
  • Discomfort 
  • Avoidance of letting you look at/in his mouth

Types

Scientifically, the yellow bristle grass plant is known as Setaria glauca and Setaria lutescens.  It is also commonly known by the name of bristly foxtail.  This plant is thought to be originally from Africa but is also said to be from the warmer regions of both the New and Old Worlds.  In the United States, it was introduced in California and is now a widespread weed.

Causes of Yellow Bristle Grass Poisoning in Horses

The yellow bristle plant can be found in clumped formations with spikelets and bristles together in dense gatherings.  This plant’s bristles, or barbed awns, on the seed head are what causes the symptoms of poisoning to develop in horses.  This plant can grow under a variety of conditions, including drought, which commonly leads to ingestion by hungry horses and therefore, an accidental toxicity.

Diagnosis of Yellow Bristle Grass Poisoning in Horses

While your horse’s symptoms may be localized to his mouth, she will want to complete a full physical exam to check for any other symptoms.  She may notice subtle signs of discomfort in other regions such as his stomach.  If uncooperative for his examination, he may need to be sedated in order to allow the veterinarian perform her exam.  It will keep him calm and cooperative while keeping both him and the veterinarian staff safe.

She will view his mouth internally and externally to evaluate his symptoms and look for the source.  If unable to see anything obvious, she may want to take a radiograph of his mouth and surrounding area to check for a cause and rule out possible diagnoses.  Another imaging option your veterinarian may employ is ultrasonography.  If your horse has developed mouth ulcers, your veterinarian will take a close look for the cause.  Sometimes in mouth ulcers of affected horses, the bristle from the plant can be found in the center.  

In addition to a physical exam, your veterinarian may suggest blood work to check for any other conditions that may be affecting your horse, especially if he is anorexic.  Lab work will involve blood tests, urine tests, and possible fecal tests to rule out other possible causes of his symptoms.  A complete blood count (CBC) and chemistry panel will give basic information on his blood levels and organ function.

Treatment of Yellow Bristle Grass Poisoning in Horses

To prevent further intoxication, you will need to immediately remove your horse from the source of yellow bristle grass.  Move him to a stall or enclosure where you can monitor what he is ingesting as well as protect him from other outside elements. There is no antidote to this type of poisoning so treatment will involve supportive care and therapies as symptoms arise.  If your horse is not eating, an appetite stimulant will be administered.  If he is not drinking he is at risk of dehydration and as a result, your veterinarian may suggest administering fluid therapy.    

Administration of pain medication may be discouraged if a stomach ulcer is suspected.  Topical pain medications may be allowed to be applied to the painful areas of his lips and mouth.  Keeping him comfortable while he recovers is the best form of treatment your veterinarian can provide.

Recovery of Yellow Bristle Grass Poisoning in Horses

Since there is no exact treatment in response to yellow bristle grass poisoning, treatment and recovery vary from case to case.  It would be best to remove the plant from your horse’s area to prevent further ingestion.  This, plus the timely treatment of his symptoms offers him a good prognosis of recovery.