It is important to check in and around the edge of paddocks for any plants which may be harmful to horses or ponies. Any harmful plants should be dug out and removed. The following plants are just some which are poisonous to horses and ponies in varying degrees.
Also watch out for garden clippings dropped into your field. Any garden plants and lawn mowings should be considered poisonous and unsafe for horses and ponies to eat. Some poisonous plants become palatable after spraying with weedkiller.
Break open hay bales and discard any plants that you cannot identify.
The major causes of poisonings in horses and ponies are:
Acorns/OAK TREES - Quercus - Both the leaves and acorns of the tree are poisonous. Some horses/ponies may develop an appetite for acorns with serious consequences, however the comsuption of small amounts is probably harmless; but to be safe fence off any oak trees during the autumn
Black Bryony, there are perils in taking bryony in any form. The sap blisters skin, and if tasted it burns the mouth and brings about vomiting and diarrhoea. Sheep and goats have eaten the herb without serious ill-effect, but horses have been fatally poisoned. In cattle the berries are irritant and narcotic
Black Nightshade A native annual found throughout most of England but becoming rarer northwards and local in Wales. Black nightshade is a plentiful and troublesome weed of agricultural and horticultural fields and gardens. It occurs on a wide range of soils but prefers soil rich in nitrogen.
Bracken can cause poisoning in stock animals although sheep and cattle normally avoid it, as do rabbits. In non-ruminants it causes a vitamin deficiency leading to staggers in horses. In ruminants, it causes ulceration and blood loss in cattle and blindness in sheep. The fronds are most toxic at the newly emerged or crozier stage. The fronds become less toxic with age but it is important that bracken cut for animal bedding should have died back entirely. The rhizomes are also poisonous and are a potential hazard to pigs that may uproot them and to cattle when ploughing exposes the rhizomes. Bracken is considered a human health hazard due to the carcinogenic spores. It also provides a habitat favoured by sheep ticks that transmit Lymes disease. Few birds breed in bracken and it is said to have limited wildlife value.
In large doses, Sparteine causes vomiting and purging weakens the heart, depresses the nerve cells and lowers the blood pressure and has a strong resemblance to the action of Conine (Hemlock) on the heart. In extreme cases, death is caused by impairing the activity of the respiratory organs. Shepherds have long been aware of the narcotic properties of Broom, due to Sparteine, having noticed that sheep after eating it become at first excited and then stupefied, but the intoxicating effects soon pass off.
Buttercups varies widely in size and habit of growth, but all have similar golden flowers and all are poisonous, but dried in hay are harmless.
Celandine - Greater
Deadly Nightshade (DEADLY/WOODY) - Atropa belladonna/Solanum dulcamara - Woody nightshade grows in woods and hedges and on beaches throughout Britain
Above - Foxglove - Digitalis purpurea. All parts on the plant are poisonous growing throughout Britain in woods, on heaths, banks, rocks in acid soils.
Above - HEMLOCK - Conium Maculatum - contains several poisonous alkaloid chemicals. All parts of the plant are poisonous. Hemlock resembles many other harmless members of the parsley family; however, its smooth, purple-blotched stems and unpleasant smell can easily identify it.
Hemlock is found by roads, streams and on waste ground throughout Britain. It is less common in the north.
Horsetail (left) Equisetum - poisoning though rare is most likely to occur from contaminated hay or straw. The effects are similar to Bracken poisoning. They are extremely difficult to kill as they have very long taproots.
Horsetail and Groundsel, commonly found in fields and roadsides, cause similar illness. Incordination, pronounced heartbeat after mild exercise and muscle tremors. If untreated this is followed by convulsions
and death. Significant intake
can lead to kidney damage
Ivy Hedra - clambers over trees and in hedgerows often reaching a great size, it produces greenish-yellow flowers in the autumn and is rarely eaten by horses and ponies.
Lily of the Valley
Potato Potatoe 1 meter tall perennial herb with an erect branched stem and underground stolons bearing tubers. Flowers resemble those of the tomato, but are white in colour. Although widely used to feed cattle and pigs, green potato tubers contain solanine, and the horse is much more vulnerable to this type of poisoning. Symptoms include salivation, diarrhoea, colic, thirst, weakness, and paralysis.
Ragwort (above) perhaps has the highest profile in plants dangerous to horses. Ragwort is a member of the daisy family and is so called because of their ragged leaves and appears in four varieties. Very dangerous when dried as it loses its bitter taste.
St Johns Wort causes photosensitation in areas of unpigmented skin, which can become red and irritated when exposed to sunlight. When dried, it is far less toxic but is still poisonous when found in hay.
YEW- Taxus baccata - is the most poisonous tree in the British Isles and even small amounts are fatal. Yew trees grow especially well on chalk. They resist pollution well and can flourish in the shade of taller trees, but little will grow in the shade they themselves cast. The bark is poisonous and so is the cut or dropped foliage. The scarlet berries are harmless, but the seeds are poisonous.
It is sometimes suggested that these were planted as a symbol of long life or trees of death. Another explanation is that the yews were planted to discourage farmers and drovers from letting their animals wander into the burial grounds, with the poisonous foliage being the disincentive.
FRUIT TREES - although not in the slightest poisonous, they are included here, because during the Autumn when they are full of fruit, the fruit can cause digestive upsets in horses and ponies and the trees should therefore be fenced off to prevent horses gorging themselves on the fruit.
Not all poisonings are fatal; sometimes the result can be serious digestive upsets, stupours or convulsions.
As a general rule poisoning should be suspected when the horse becomes suddenly ill after feeding; especially when put out to pasture for the first time in the season, the grass is scarce, but succulent young growth of poisonous plants is tempting. During dry periods when the grass is parched, or in the autumn/winter when grass is short and extra feed is not provided horses will eat what is available even if it has a bitter taste or is something they would not normally eat.
If you suspect your horse of having eaten parts of poisonous plants or trees, or the horse shows any unusual symptoms call your vet immediately.