Please note that the term ‘horse’ is used on this page, but the information applies to horses, ponies and donkeys.

Find out more about the most common, potentially serious poisons that can affect horses and learn what symptoms to look out for and what treatment is likely to be required.

Ragwort (Senicio Jacobae)
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.

Signs of ragwort poisoning are usually delayed and may include abdominal pain, constipation or diarrhoea, severe straining, rectal prolapse, weakness, weight loss, restlessness, unsteadiness, blindness, breathing difficulties and head pressing [1]. Some horses develop kidney or liver damage. Managing weeds

Consult a vet urgently if you suspect your horse has eaten this plant.

[1] Head pressing is a postural disorder characterised by a horse apparently stabilising their head through contact, persistent pushing, against a vertical surface

Phenoxy acid herbicides
Phenoxy acid herbicides [2] are a type of weed killer commonly used on garden lawns. Other types of weed killer are available and may also be toxic to horses. Poisoning occurs when recently treated plants are eaten.

Poisoning can result in abdominal pain, diarrhoea, problems swallowing, lethargy, twitching and fitting. Some horses develop kidney or liver damage.

Consult a vet urgently if you suspect your horse has been exposed to this poison.

[2] Phenoxy acid herbicides include 2,4-D, 2,4,5-T, 2,4-DB, MCPA, MCPB, MCPP and dichlorprop.

Rodent poisons (‘rodenticides’)
The following specifically refers to anticoagulant rodenticides [3]. Other types of rodenticide are available which may also be poisonous to horses [4]. Anticoagulants act by preventing blood clotting.  These products are commonly used to control rodent infestations. The baits are usually coloured blue or green (sometimes purple or red) and can be sold in the form of a powder, paste, seeds or grains.

Poisoning may result in life-threatening bleeding; effects may not appear for several days. Bleeding may be internal and therefore is not always visible. Occasionally lameness may develop due to the horse’s joints swelling.

Consult a vet urgently if you suspect your horse has been exposed to this poison.
Most horses will require a course of the antidote. Blood tests may confirm poisoning.

[3] These include brodifacoum, bromadiolone, chlorphacinone, coumatetralyl, difenacoum, diphacinone, coumatetralyl, difenacoum, diphacinone, flocoumafen and warfarin
[4] Not all rodenticides are anticoagulants; it is important to check which one your horse may have eaten.

Yew tree (Taxus baccata)
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.

Signs of toxicity may include diarrhoea, weakness, unsteadiness, collapse, breathing difficulties, tremors and fitting.

Signs may develop rapidly, and sudden deaths can occur.

Consult a vet urgently if you suspect your horse has eaten this plant.

Leyland Cypress (Cupressocyparis leylandii)
All parts of this plant are potentially toxic.

Signs of toxicity may include loss of appetite, colic, diarrhoea, tremor, weakness, depression, high temperature and laminitis (inflammation of the laminated tissue that attaches the hoof to the foot of a horse).

Consult a vet urgently if you suspect your horse has eaten this plant.

Oak (Quercus spp)
Oak poisoning usually occurs in either the spring (from eating young shoots) or in the autumn (after eating acorns and fallen leaves).

Horses may not become unwell until several days after the poisoning incident. Poisoning can result in constipation, diarrhoea (which can contain blood), depression, colic, swelling of the neck and throat, red or brown urine, weakness, sweating and unsteadiness. In severe cases some horses may develop fits, breathing difficulties and coma.

Consult a vet urgently if you suspect your horse has eaten this plant.

If you think your horse, pony or donkey has been poisoned, contact your vet immediately.

You can also read our top tips for more information on what to do if you think your horse, pony or donkey has been poisoned: Poisoning in equines.

Acknowledgement for this information is made to The Veterinary Poisons Information Service (VPIS). The VPIS is a specialist 24-hour emergency service, which is only available to veterinary professionals and animal welfare organisations, providing information and advice on the treatment of animals exposed to toxic substances. It is not a public access service. Some helpful information is available on their website www.vpisuk.co.uk.