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What is Wild Mustard Poisoning?

As noted above, as a member of the mustard family (Cruciferae Brassicaceae), wild mustard, also known as Brassica Kaber (DC) and charlock, is a weed commonly found in pastures and fields.  This weed can be an annual or perennial and is considered toxic to horses when the seeds and plants with seed capsules are ingested in various quantities by your horse.  Virtually all parts of this plant are considered toxic to horses.

Wild mustard, hailing from the Brassica or mustard family, is a plant which is commonly found in pastures all over the United States and has been reported to be toxic to a variety of species of both ruminants and non ruminants.

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Symptoms of Wild Mustard Poisoning in Horses

While there are symptoms which accompany the ingestion of a variety of species of the mustard family, for purposes of this condition guide, we will focus on wild mustard (brassica kaber) and the commonly caused symptoms of gastroenteritis:

  • Pain
  • Salivation
  • Diarrhea
  • Disturbances of the upper gastrointestinal tract
  • Irritation of the mouth and oral ulcers
  • Colic
  • Head shaking

More rare symptoms include:

  • Abortions
  • Goiter
  • Blindness

It is believed that the toxicity of the plant increases when the plant is flowering, though the seeds and virtually all other parts of the plant have been shown to be quite toxic as well.

Types  

Wild mustard (Brassica Kaber) also includes charlock, California rape, Chinese mustard, Gal choy, and brown mustard.  Any “typing” that is associated with the poisoning would be as applicable to the variety of the plant within the mustard family which was consumed by the horse. Certain varieties of the mustard family are known to cause a condition called Congenital Hypothyroid Dysmaturity Syndrome in foals.  This condition is thought to be the result of ingestion of any of several varieties of mustard plants during late pregnancy and generally show signs of:

  • Abnormally long pregnancy
  • Foals born with facial and lower jaw deformities
  • Limb deformities

Causes of Wild Mustard Poisoning in Horses

The toxin responsible for wild mustard poisoning in horses is sinigrin, also known as potassium myronate, which is defined as “a colorless, crystalline, water-soluble solid, found in the seeds of black mustard” and has been found to deter some predatory insects.  Sinigrin, when accompanied by the enzyme myrosinase, is known to be converted into a dangerous triad:

  • Glucose 
  • Allyl isothiocyanate (also known as mustard oil) 
  • Potassium hydrogen sulfate.  

The poisonous component of this triad is the mustard oil, causing the toxicity symptoms noted above, sometimes with a toxic concentration of nitrate to add to the mix.  When this mustard oil is created through the digestive process, it causes the acute gastric symptoms noted above as well as the congenital hypothyroid dysmaturity syndrome in foals also noted above.

Diagnosis of Wild Mustard Poisoning in Horses

When your veterinary professional evaluates your sick horse, he will need a complete history from you that covers not only the symptoms you’ve noticed and the duration of those symptoms but also the horse’s feeding regimen and feed offered, the frequency of pasturing versus grain and hay feedings, the presence and composition of the pasture, hay and forage being fed and whether there are other equine in your herd who may be exhibiting earlier symptoms.  

The veterinarian will do a thorough physical examination of your horse and will likely order some lab testing of blood and various fluids and tissues to determine abnormalities in the chemistry of the afflicted animal.  Since the symptoms of wild mustard poisoning can be similar to many, many other conditions and poisonings of horses, he may wish to order radiographic imaging (x-rays) and even CT scans to rule out the possibility of lesions or masses.  Once he has collected this information, he will be able to develop and initiate an appropriate treatment plan for your horse’s affliction.

Treatment of Wild Mustard Poisoning in Horses

The first treatment recommendations likely to be given to you by your veterinary professional will likely be to remove the afflicted equine from the pasture or other source of the potential poisoning, provide nutritious and safe feed and place the horse in a quiet, restful place to recover and heal.  Once the afflicted equine has been removed from the source of the poisoning, fluids will likely be recommended along with rest and perhaps some anti-diarrheal medication being administered to stabilize any continuing fluid loss.  There is no antidote for mustard poisoning, with supportive care being the standard of care for this type of poisoning.  

Continued monitoring and observation will be needed as well as perhaps some follow up care by your vet depending upon the degree to which your horse has been poisoned.  It may take several weeks or months to recover from wild mustard poisoning and, during this time, the horse should be allowed to rest, be given plenty of clean, safe water and nutritious feed.  It is important to be sure not to feed hay or grains which contain mustard seeds or plants and keep them out of fields or pastures which are heavily infested with this weed to avoid future episodes of this poisoning.

Recovery of Wild Mustard Poisoning in Horses

As noted above, it may take several weeks or months for your afflicted equine to recover from the poisoning of wild mustard.  Additionally, it will be necessary to closely monitor the horse while it is recovering to ensure that it is responding as expected.  For the future health of the afflicted horse as well as that of the remaining horses in your herd, it is vital to manage the pasture and fields in which you allow your herd to forage as much as possible, eliminating wild mustard as well as other poisonous and toxic plants to the best of your ability.  It is in the best interests of your financial investment as well as the health of your herd that you do all that you can do to avoid future episodes of plant poisonings of your horses.