Hoary Alyssum Poisoning Average Cost

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What is Hoary Alyssum Poisoning?

Hoary alyssum, scientifically known as Berteroa incana, is a weed that can branch out up to 3 feet high. It is a toxic plant that grows within the United States, except in the states of California, Arizona, and other southeastern states. It tends to grow well in cool weather as well as in the hot, dry summer seasons of many of the northern states, as well as Canada. The leaves of the Hoary alyssum have a very narrow and oval-shaped appearance that taper off at the end. The leaves are adorned with thin, white hairs in the flowers of this weed are white with four petals. This weed has pods that contain roughly six small seeds that are brown in color. 

This toxic weed is a member of the Brassicaceae family, known as the mustard family, and is called several different names such as false alyssum. The noxious weed will continue to invade property or pasture if it is not kept under control by the horse owner. It should frequently be treated with herbicides or mowed.

Hoary alyssum is a poisonous weed to horses and is often found in the hay they may eat. The precise toxin within Hoary alyssum is unknown; however, horses that ingest this weed can become ill and require medical attention.

Symptoms of Hoary Alyssum Poisoning in Horses

If your horse has ingested Hoary alyssum, he can present a variety of toxic symptoms. Symptoms of ingesting this weed, even in dried form, include:

  • Diarrhea
  • Dehydration
  • Hypovolemic shock
  • Lameness
  • Swelling of the legs
  • Laminitis
  • Stiffness
  • Pain in the abdomen
  • Aborting of fetus (pregnant mares)


Hoary alyssum is also called several different names, and knowing the different name types is important if you are a horse owner. Other types of names this plant is referred to are:

  • Heal bite
  • Hoary berteroa
  • Hoary false alyssum
  • False hairy madwort
  • Madwort

Causes of Hoary Alyssum Poisoning in Horses

The causes of Hoary alyssum are currently unknown. Medical researchers do have knowledge of this plant and how it may play a role in making horses ill, which are:

  • Not all horses react to the toxin in the weed
  • Any breed, type of horse, or gender, can be affected
  • Horses that are housed may be affected more often, such as racehorses
  • Feeding of baled hay increases the risk of Hoary alyssum poisoning
  • Pasture that contains the weed puts horses at risk

Diagnosis of Hoary Alyssum Poisoning in Horses

If you suspect your horse has symptoms of toxicity, make an appointment with your veterinarian. Your veterinarian will look closely at your equine’s symptoms and ask questions pertaining to the severity and timing of those symptoms. 

Your veterinarian will begin by conducting a complete physical examination of your horse. As he may suspect poisoning, he may need to move quickly in order to come to a diagnosis so he can treat him in a rapid manner. In addition to learning about your horse’s history, he will perform a complete blood count to gather information about any abnormalities within the blood stream.

Your veterinarian will also perform a biochemistry profile, serum analysis, urinalysis, and possibly radiography to come to an accurate diagnosis, as well as rule out any other secondary health conditions. Your medical professional may go ahead and administer activated charcoal, as when the laboratory tests come back there will be a sign of toxicity in his system. Activated charcoal absorbs toxins within your horse’s stomach and prevents them from further entering the blood stream and other organs.

Treatment of Hoary Alyssum Poisoning in Horses

If your horse has been diagnosed with Hoary alyssum poisoning, your veterinarian will recommend several methods of treatment. Treatment may include:

IV Fluids

Support therapy with IV fluids can help restore hydration, especially if diarrhea has occurred. Electrolytes are also replenished with intravenous fluids. Other support therapy may include treating of any limb edema with cool water hydrotherapy.

Anti-Inflammatory Drugs

Phenylbutazone or flunixin may be given for their anti-inflammatory benefits. This can also help prevent laminitis, or founder. If a horse should come down with laminitis, the tissues of the hoof wall can become painful and inflamed.


Your veterinarian may need to keep your horse overnight or for a few days to be sure he is recovering and his symptoms are diminishing. This depends solely on your horse’s reaction and level of toxicity, which is determined by laboratory testing.

Recovery of Hoary Alyssum Poisoning in Horses

In most cases of Hoary alyssum poisoning, horses recover well. In rare cases, this condition can be fatal if left untreated and if the toxic weed is not completely removed from horses’ hay and diet. Many horses do recover within a few days once the toxic substance is flushed from the system.

This poisoning can be prevented by making sure measures are taken to eliminate the weed from the pasture and hay. This can be accomplished by using herbicides and other significant weed control. If left uncontrolled, Hoary alyssum is an invasive weed that can pose risk to horses.

If your horse has been treated, your veterinarian will give you instructions on how to further take care of your horse at home. It will be important to administer any medications according to your veterinarian’s instructions. If you observe any new symptoms in your horse, contact your veterinarian. He may want to see him again and run laboratory tests once again to be sure your horse is improving.