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What is Toadflax Poisoning?

Toadflax (scientific name Linaria vulgaris) is a perennial that has smooth and erect stems that grow to be up to two feet tall, emerging in clumps from a spreading root system. Also known as yellow toadflax, the leaves of plant are narrow, soft and gray-green in color, measuring about 1 to 1 ½ inches long. The plant includes yellow flowers (similar to those of snapdragons) that have an orange spot on their lower lip. Flowers grow in clusters (about 15-20).

The plant reproduces through seeds and creeping roots (root system includes horizontal spreading roots along with secondary roots). Toadflax contains alkaloids and glycosides, which are toxic to horses. Typically, horses will avoid eating the plant; however, can experience toxicity as a result of it being included in their hay.

Toadflax, also called yellow toadflax, contain alkaloids and glycosides that can be toxic in horses; horses will typically avoid eating the plant; however, hay with a high amount of toadflax can lead to gastrointestinal upset.

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Symptoms of Toadflax Poisoning in Horses

Should your horse ingest toadflax, they may experience gastrointestinal upset, which can include colic and diarrhea. Fortunately, symptoms of toadflax poisoning are relatively minor in comparison to those of other toxins.

  • Diarrhea
  • Gastrointestinal upset
  • Colic

Types 

Toadflax is also known as yellow toadflax. The flowers of the toadflax are smaller than those of  the Dalmatian toadflax (scientific name Linaria dalmatica). Chemical analysis of Dalmatian toadflax shows that it has a high level of iridoid glycosides (up to 17.4% of the plant’s dry weight). Toadflax may be called any of the following names:

  • Bread-and-butter
  • Brideweed
  • Butter-and-eggs
  • Flaxweed
  • Gallwort
  • Wild snapdragon
  • Wild flax

Causes of Toadflax Poisoning in Horses

Toadflax contains quinazoline alkaloids, vasicine, vasicinone, quercetin, acacetin and deoxyvasicinone, with the concentration varying throughout the growing season. The plant also contains several flavonoid glycosides to include linarin and linarisan and the cyanogenic glucoside prunasin.

The alkaloid concentration will vary throughout the growing season. Fortunately animals tend to avoid eating this plant, however poisoning can occur should your horse be fed hay that has a high amount of yellow toadflax.

Diagnosis of Toadflax Poisoning in Horses

If you notice unusual gastrointestinal symptoms in your horse, contact your veterinarian, who can conduct a physical examination. Your veterinarian will ask you about the symptoms you have noticed in your horse, when you first noticed them and any changes that you have observed. You will also be asked about your horse’s diet. If you noticed your horse ingest toadflax, or any plant that you are concerned may have been problematic, bring a sample of the plant with you. This may help your veterinarian in making a diagnosis.

In addition to getting your horse’s vital signs, your veterinarian will take a complete blood count, request a chemistry panel and packed cell volume (PCV). A urinalysis can help in assessing kidney function. Your veterinarian may also seek to study the feces of your horse to determine if your horse ingested something that can be causing his symptoms.

Treatment of Toadflax Poisoning in Horses

When poisoning is a concern, your veterinarian will want to clear the plant material and toxins from your horse’s system. Activated charcoal may also be used to absorb any toxins remaining before your horse’s body absorbs them. Fluid therapy may be utilized in order to help flush the toxin from your horse’s body, as well as to prevent dehydration that may result from diarrhea. Medication may be administered in order to help with any nausea that your horse is experiencing as a result of the toxicity.

Recovery of Toadflax Poisoning in Horses

Should your horse experience toadflax poisoning, you will want to follow the recommendations of your veterinarian in order to help him best recover. The poisoning in your horse will likely be mild; with some rest and by remaining hydrated, your horse will likely make a good recovery.

It is a good idea to regularly roam the areas where your horse has access in order to determine if there are any toxic plants that may lead to poisoning in your horse. These plants should be removed so that your horse does not consume them and become ill.