Horses can become very ill after ingesting toxic plants or chemicals. This can cause damage to the gastrointestinal tract as well as other internal organs.
Some plants, such as foxtails cause mechanical damage as they injure mucosal surfaces of the mouth, eyes, ears, skin folds, and migrate through soft tissues. Avoiding contaminated hay and maintaining pastures to avoid exposure is recommended. Furthermore, some plants have indigestible fibres, burrs, and some poorly identified plant parts that cause concretions in the gastrointestinal tract, especially in the equine colon, where they increase in size until they intermittently or permanently obstruct colonic function and flow. Persimmon can cause epidemic outbreaks of equine gastric blockages and colic.
All parts of the plant are poisonous. Ragwort is said to be unappetising to horses and is usually only eaten when there is little choice of other plants. Dried ragwort remains toxic, but seems more appealing to horses.
The often-fatal muscle condition Atypical Myopathy (AM) has become common in Britain and can be triggered by the ingestion of sycamore seeds, leaves and seedlings.
All parts of the yew tree, apart from the fleshy fruit, are poisonous to animals (including the seeds within the fleshy fruit). Poisoning can occur all year round and even dried material can be toxic.
If you think your horse / pony has been poisoned, contact your vet immediately to give them the best chance of survival.