Bryony Plant Poisoning in Horses

By PetMD Editorial on Nov. 2, 2011

Bryonia dioica Toxicity in Horses

Bryonia dioica, or bryony, is an invasive plant that is known to climb buildings, trellises, fences, barns, stables, homes, trees, and even over other hedges. It is most often found in hedgerows and open wooded areas, and grows most vivaciously in areas with a temperate climate. In the U.S., the bryony plant is more commonly found in the Northwest states.

Both white bryony and black bryony are known for being highly toxic to the intestinal tract. While the whole plant is toxic to a horse (i.e., leaves, berries, vines), the berries and roots of the plant hold the most poison. The coloring of the berries is best way to distinguish between the two types of bryonies. While both plants’ berries begin green, the white bryony's berries ripen to black colored berries, while the black byrony's berries ripen to red colored berries. The plant is described as having an unpleasant odor, so horses will generally not eat from the plant as a first option, but may do so if left without other suitable forms of feed.

Knowing what the bryony's leaves and berries look like, and ensuring that your horse does not have access to it, is critical to protecting your horse from the plant's toxic effects. 


The main side-effect of bryony toxicity is as an intense laxative. Some of the symptoms that may be seen are:

  • Soft stool, diarrhea
  • Excessive urination (polyuria)
  • Elevated temperature
  • Profuse sweating
  • Trouble breathing (dyspnea)
  • Muscle tremors
  • Muscle spasms


  • Ingestion of the bryony plant  - especially the berries and roots
  • Ingestion of any part of the plant may have a toxic effect in the intestinal or respiratory system


It often proves difficult to determine the exact cause of poisoning in a horse. A veterinarian should always be consulted when some type of poisoning is suspected, and especially so if you have determined that you have a poisonous plant growing on or near your property, and your horse is exhibiting symptoms of illness. Your veterinarian will perform a thorough examination, which may also include blood and urine analysis. These tests will not tell the veterinarian exactly what toxin has been ingested, but will give clues to the damage that is occurring in the horse so that proper medical action may be taken.


There is no specific course of treatment for poisoning by the bryony plant. Sometimes symptomatic therapy can make things a great deal easier, especially in the cases that are known to be less severe.

In cases with diarrhea, fluid therapy is standard treatment for lessening the likelihood of dehydration and shock. If the cause of the toxicity can be traced to a plant, the use of active charcoal therapy can be used to some effectiveness in neutralizing the toxin and promoting its expulsion from the body. Sometimes paraffin treatment has been proven to be useful in some instances of poisoning as well. Occasionally, an anti-inflammatory such as flunixine meglumine may be given, as well as systemic antibiotics which will help prevent secondary bacterial infections.

Living and Management

It is a part of responsible horse ownership to ensure that your horse does not have access to the types of plants that pose a threat. This is not always possible to do, but knowing what to look for, and taking regular inventories of the areas in which your horse roams, is essential.

In as much as you are capable of doing, if you find bryony (or any poisonous plant) growing in your area, remove the plants and all of its roots. Often, the plant will be too closely attached to another plant that is either difficult to remove, or that the owner of the land does not wish to remove (such as a large tree). In these cases, removing as much of the plant as possible, and returning to the area to remove new growth may be the best preventative possible. Alternatively, restrict your horse’s access to areas populated by toxic plants. This can be done easily with a simple electric fence.


Because horses will graze on the greenery of the area in which they roam, it is important to be aware of what is growing in your area. Birds are frequent disseminators of seeds and berries, so plants may quickly take up residence in a spot in which they did not reside before. Taking regular inventory of the area that is accessible to your horse is the best way to prevent poisoning. Research of the plants that are commonly found in your zone, along with knowledge of the known symptoms of plant toxicity are always helpful in protecting your horse's well-being.

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