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Horses usually avoid privet due to its odor when bitten into, but ingestion does occasionally happen. This evergreen shrub is part of the Oleaceae, or olive family, and can often be found in hedgerows, near fences, at abandoned farms, and in the woods or bottomlands. Privet can grow up to 15 feet tall, with panicles of small, white flowers, and black or dark blue berries that can be seen even in winter.
Privet, a common ornamental hedge, contains leaves and berries that are poisonous to horses. When consumed, privet mainly causes gastrointestinal distress, but it can also affect the nervous system, causing convulsions, paralysis, and even death.
Privet poisoning can be quite severe, and though rare, death can occur within 4 to 48 hours after ingestion. Symptoms include:
The cause of privet poisoning lies in the glycosides found in the leaves and berries of the plant, with the berries having the highest concentrations. Terpenoid glycosides are believed to be the main toxic principle in privet, such as ligustrum, syringin, and oleuropein. The toxic glycosides reside in a compartment of the plant separate from any activating enzymes. When a leaf or berry is destroyed through chewing by an animal, the enzymes mix with the glycosides, which activates the protein disruption action of the glycosides. This completely decreases any nutritive value of protein eaten in the diet, and causes the adverse effects seen in a horse who has ingested privet.
There are insects and some animals who can safely consume privet, due to an adaptation that allows them to secrete free glycerine into their digestive juices. Horses, however, do not have this adaptation.
If you have witnessed your horse eating privet, or have seen privet contained in your horse’s feces, it will be easy to diagnose this condition based on symptoms and the presence of the toxic plant. Bring any samples of the plant you believe your horse has eaten to your veterinarian to positively identify.
Diagnosis of a plant poisoning can be more difficult if you do not know your horse has eaten something toxic. Be sure to tell your veterinarian of any medical history of symptoms. Your veterinarian will perform a physical exam, and will run many tests to narrow down the cause of the symptoms. These can include blood tests, serum analysis, and a urinalysis, all of which can often show the presence of alkaloids or other plant toxins. Feces and residual material found in the mouth or on the teeth can also be examined for plant parts, which can also positively identify and diagnose the cause of your horse’s distress. The contents of the stomach could also be examined, but this is often done post mortem.
Due to the severity of possible life threatening conditions that can occur with plant poisonings, your veterinarian may begin supportive treatment before a positive identification can occur, depending on the condition of your horse.
There is no specific treatment for privet poisoning, but therapy will be supportive and aim to treat the symptoms and stabilize your horse. This can include fluid and electrolyte therapy.
If your veterinarian believes that a very large amount of the toxin was eaten, activated charcoal or mineral oil may be given to reduce absorption of the toxin.
Removing the source of the poisoning is important to your horse’s health. Be sure there is no privet within reach of your horse, and check hay and feed for cross contamination, removing any that has been mixed with privet.
Recovery prognosis is good for your horse, as long as privet is removed from your horse’s diet, and prompt medical care has been sought. Ingestion of privet can cause death, but it is rare.
Since horses will not normally seek out privet as a food source, prevent your horse from accidentally eating this toxic plant through these strategies:
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