Watch out for poisonous plants
Bracken Fern
This common fern plant can be found in many areas of Britain but does not like poorly drained land. Ingesting this plant can cause weight loss, staggering, nervousness, muscle twitching and seizures in horses. This plant is life-threatening if eaten over a long period of time and not treated.
Buttercup
These small yellow flowers are found in pastures all over the country and appear innocuous but can be poisonous to horses if eaten in large quantities. Symptoms of ingestion include mouth ulceration/inflammation/blistering, swollen face, salivation and seizures.
Although it can be life-threatening, the effects caused by
eating the plant normally stop the horse from eating it, thereby limiting its
effects. As with many poisonous plants, horses would not choose to eat
buttercups unless there was no alternative.
Charlock
Also known as wild mustard, Charlock is predominantly found on heavy clay soil and flowers from May to July. This annual weed causes frothing at the mouth, diarrhoea, bloating and even breathing difficulties in horses and can be fatal if eaten in large amounts.
Cowbane
Cowbane is a common weed that is most poisonous to cattle but is also dangerous to horses. The poisonous element is called Cicutoxin but it is contained within the roots rather than the stem or leaves so it is fairly unlikely to be eaten by horses. If the poison is ingested it is very dangerous to horses and can cause dilated pupils, convulsions and colic. It can be fatal within the first few hours of ingestion but if the horse survives the first few hours a full recovery is likely in only a few days.
Horsetail
This weed is widely distributed in meadows and grows strongly on pasture land. It is toxic to sheep, cattle and horses in both its green state and dried in hay. Ingestion of this weed is life-threatening if left untreated and is a common cause of serious or fatal poisoning in horses. Symptoms include tremors, cardiac problems and kidney damage.
Laburnum
All parts of the laburnum tree are poisonous, and not just to horses. If consumed in large quantities it can be life-threatening and causes diarrhoea, salivation, colic, convulsions and dilated pupils.
Foxglove
This attractive flowering plant (pictured) is well known to be poisonous to humans but is also dangerous for a number of animals. The toxin digitalis can cause irregular heart beat and even heart failure fairly quickly and is therefore life-threatening. Horses would usually only eat it in its dried form, for instance in hay, so farmers must beware of this deadly plant when harvesting and baling.
Hemlock
Hemlock is a common pasture weed in the UK and the entire plant is poisonous. The active principles are several alkaloids, all of which are poisonous but the most important is coniine. Hemlock is toxic to cattle, sheep, horses, goats, pigs and poultry. Animals are most likely to be affected by eating contaminated forage. Management includes removal of the plant prior to seeding in spring as well as regular mowing to kill mature plants.
Ingestion causes death by respiratory paralysis.
Monkshood
Reputed to be one of the UK’s most poisonous plants, Monkshood can cause sudden death form asphyxia and circulatory collapse, however the plant is rare so the risk of consumption is low. Monkshood is a perennial herb with tuberous fleshy roots, erect stout stems and violet-blue flowers with hoods. All parts of this plant are poisonous and can cause a severe allergic reaction in humans so must be handled with gloves to prevent absorption through the skin.
Oak
The leaves and acorns of the oak tree are poisonous to cattle, horses, sheep, and goats in large amounts due to the toxin tannic acid. Oak leaves and acorns can cause symptoms such as lack of appetite, depression, constipation, diarrhoea, blood in urine, and colic. Oak is also palatable to horses, so once they have a taste for the leaves and acorns, they may seek them out and poisoning can be life threatening.
Potato
Potato can be poisonous if the horse is able to eat decayed, sprouting or green tubers. Although uncommon, poisoning can be fatal.
Privet
This common shrub is often used in gardens as it makes a strong border, but is not suitable to edge paddocks as it is poisonous to horses. The effects can be life-threatening and death can occur within 48 hours of ingestion.
Ragwort
Ragwort is one of the most commonly reported poisonous plants, perhaps because of its distinctive yellow flowers. Even small amounts of ragwort can cause serious health problems in horses, including loss of weight and condition, jaundice and photosensitive dermatitis. One of the most serious symptoms of ragwort poisoning is liver damage, which builds up over time. Symptoms may not even appear until 75% of the liver has been irreparably damaged.
Ragwort is bitter-tasting so is usually avoided unless grazing is in short
supply. However, it does become more palatable when cut and wilted, so must be
carefully pulled up and destroyed by burning.
In the United Kingdom, Ragwort is classified as injurious by the 1959 Weed Act,
making it is an offence to allow it to spread.
Yew
Most parts of the tree are toxic and the foliage remains dangerous even when wilted or dried. Horses have a low tolerance, with a lethal dose of 200–400 mg/kg body weight, but cattle, pigs, and other livestock are only slightly less vulnerable. Symptoms include staggering gait, muscle tremors, convulsions, collapse, difficulty breathing, coldness and eventually heart failure. In many cases there are no signs as acute heart failure can lead to death within a few hours.
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