background source: esiowa.com
We tend to paddock our horses every day, especially during summer. But do we wonder what dangers await them while being on a pasture? We provide them with shadow on hot days, access to water and protection from insects - but it might not be enough if there are some poisonous plants among grass and trees. They are a frequent cause of food poisoning, diarrhoea and illnesses that are difficult to diagnose. These conditions might be caused by harmful substances present in plants: essential oils, mycotoxins, nitrites, colloids, coumarins, and alkaloids.
Every year many horses have poisoning because of eating poisonous plants. Unfortunately, due to lack of reaction or late interventions, some of these poisonings turn out to be fatal. Thus remember to always call a veterinarian in a situation when you notice some alarming symptoms after coming back from a pasture or while still being there. Only a vet can tell what eventually could cause your horse's health deterioration.
Nevertheless, it is easier to prevent than to rescue and treat. Which is why, in this article we present you with plants that are considered poisonous to horses. We will also write how to identify poisoning from a certain strain and how to give first aid before the veterinarian's arrival.
Poisonous plants:
Black locust
(l. Robinia pseudoacacia)
source, from left: tipdisease.com, 123rf.com
The whole plant is harmful, especially its leaves, seeds and bark, which contains poisonous glycoproteins, as well as rare amino acids.
Symptoms of poisoning:
- precipitated pulse and breathing
- convulsion
- spasms
- suffocation
- colic symptoms
- diarrhoea
- dilated pupils
- apathy
- limbs inertia, symptoms of paralysis
First aid:
- administer activated carbon as soon as possible
- call a veterinarian, he or she would intravenously hydrate your horse
- fatal cases are very rare
Ground-ivy, gill-over-the-ground, creeping charlie, alehoof, tunhoof, catsfoot, field balm, run-away-robin
(l. Glechoma hederacea)
source, from left: delawarewildflowers.org, lmo.wikipedia.org
The whole plant is poisonous. Horses usually get poisoned in their stables, because it gets to their feeding racks with hay.
Symptoms of poisoning:
- excessive sweating and salivation
- the horse is foamed on all his body's surface (neck, croup, head, chest etc.)
- breathing dysfunctions, hyperventilation
First aid:
- you should call a vet and leave the horse in his stall for a few days, providing him with proper care
- fatal cases are rare
Common box, European box, boxwood
(l. Buxus sempervirens)
source: svaz-skolkaru.cz
Evergreen, usually densely branched shrub or little tree. All the plant's parts, especially its leaves, branches and rind consist a mixture of poisonous alkaloids that interfere with the central nervous system.
Symptoms of poisoning:
- rapid spasm
- diarrhoea
- lethargy
- reflux (backflow, as of gastric acid into the esophagus)
- convulsions
- respiratory distress
First aid:
- calling a vet is crucial, because as little as 750 g of its leaves is lethal for a horse
- it is worth administering activated carbon before the vet's arrival
Yew, English yew, European yew
(l. Taxus baccata)
source, from left: bioinformatics.psb.ugent.be, horsedvm.com
It is a strain planted as a decorative one, unlike other conifers it does not have cones. All the plant's parts (except for seed's covers), especially the needles are poisonous - as little as 50 g is a deadly dose for a horse.
Symptoms of poisoning:
- movement and circulatory system dysfunctions
- diarrhoea
- colic symptoms
- heart and respiratory system paralysis - animal's death
- the effects are:
- kidney and urinary bladder impairment
- weakening of heart muscle
First aid:
- Necessarily call a veterinarian! Yew is one of the most dangerous plants for horses.
Oak
(l. Quercus)
source: allessentialherbs.com
Strong and long-living tree, which is common around pastures that are located near forests. Dangerous for horses are leaves and acorns - both the ripe ones (brown) as the unripe (green). They contain a toxic tannin, which strongly irritate digestive system during digestion. Horses should instinctively avoid eating acorns due to their unpleasant, bitter taste. However, it happens that they like this taste and even seek for this "treat."
Symptoms of oak's leaf/acorn poisoning:
- diarrhoea
- constipation
- colic symptoms of various intensity
- mucus and blood in the horse's feces
First aid:
- administer painkillers and spasmolitycs
- paraffin oil is useful in enduring constipation
- if you are dealing with massive diarrhoea, it is worth administering activated carbon to the horse
Perforate St John's-wort, common Saint John's wort, St John's wort
(l. Hypericum perforatum)
source: tisyachelistnik.ru
It belongs to plants that cause photosensitisation at horses, namely plants that exacerbate vulnerability to harmful effect of sunlight and contribute to sunburns. St John's wort works like that even when it is dried and very scarce in the horse's hay. Photosensitisation is caused by a substance called hypericin that the plant contains.
Symptoms of poisoning:
- skin irritation
- burns caused by solar radiation
- redness
- swelling
- touch-sensitiveness
- blisters, erosion, weeping
First aid:
- symptomatic treatment, you should call a veterinarian, who would prescribe proper cure
- in order to avoid such problems in the future, it is good to use sunscreen with high UV filter on white horses
Greater celandine
(l. Chelidonium maius)
source: naturespot.org.uk
Most usually it grows in shaded places, on the skirts of a forest. It is considered to be a common weed. Its juice contains various alkaloids that cause inflammation of digestive system mucosa. The whole plant is poisonous.
Symptoms of poisoning:
- colic symptoms
- consciousness disorder
- faltering
- imbalance
- inability to stand on his own legs
First aid:
- you have to call a vet as soon as possible!
- horses die due to collapse caused by acute cardiorespiratory failure
Buttercup
(l. Ranunculus)
source: desktopwallpaperhd.net
All the plant's parts contain poisonous saponins, including protoanemonin of sharp, spicy taste - it should not encourage the horses to eat it. The plant's bulbiform roots have the most dangerous toxins. It causes irritation of digestive system mucosa - oral cavity, digestive system, inflammation of kidneys, but also heart failure.
Symptoms of poisoning:
- excessive salivation
- diarrhoea
- colic
- oral cavity painfulness
First aid:
- sluicing the oral cavity with antiseptics (solution of potassium permanganate, soda)
- administering activated carbon
- it is worth calling a veterinarian, so he or she could administer painkillers from the group of corticosteroids and non-steroidal
Horse-chestnut, conker tree
(l. Aesculus)
source: lookfordiagnosis.com
Dangerous, especially for young and generally impaired horses, are young buds and seeds.
Symptoms of poisoning:
- colic symptoms
- balance issues
- irregular gait
- diarrhoea and constipation alternate
- convulsion, including those of single muscles
First aid:
- administer activated carbon
- calling a vet is necessary
Lily of the valley
(l. Convallaria maialis)
source: walterblom.nl
It can be found in lighted deciduous forests and thickets, but also in mountain terrains. Sometimes it is planted for ornament. All lily of the valley's parts consist of glycosides and saponin that are highly influential on the cardiac muscle. However, leaves and stems are the biggest threat. Their consumption results in stomach and bowels irritation, cardiac arrhythmias.
Symptoms of poisoning:
- convulsion and other symptoms from the nervous system
First aid:
- call a veterinarian as soon as possible, lily of the valley poisoning may be fatal for the horse
Red maple, swamp, water maple, soft maple
(l. Acer rubrum)
source, from left: plants.ces.ncsu.edu, selectree.calpoly.edu
This tree is popular as an ornamental tree in many countries due to its beautiful red leaves during autumn. The leaves are not poisonous for horses when they grow, but they are when they fall down. After digestion, their toxic compounds enter the horse's blood stream and cause haemoclasia. If that process is not stopped in time it causes damage to kidneys which eventually stop functioning.
Symptoms of maple leaves poisoning:
- initially lack of appetite, apathy, reluctance to move
- jaundice
- anaemia
- general impairment
First aid:
Henbane, black henbane, stinking nightshade
(l. Hyoscyamus niger)
source: plantotheday.blogspot.com
Known as a commonly found weed. All its parts contain poisonous alkaloids: scopolamine and hyoscyamine, which initially work stimulating, but then they cause paralysis (sometimes even death due to cessation of bodily functions, namely breathing). Especially dangerous to horses are roots and seeds.
Symptoms of poisoning:
- drying of mucosa
- initially, motor activation
- later, apathy, anxiousness, inertia, limbs paralysis and colic symptoms
First aid:
- call a veterinarian as soon as possible
Lupin, lupine
(l. Lupinus)
source: tcpermaculture.blogspot.com
It can be found on the skirts of forests and fields. Wild lupins contain, especially in ripe seeds, various alkaloids, for example lupinine and sparteine, which might cause even the animal's death. The youngest parts of lupin are also poisonous, as they irritate the digestive system after consumption.
Symptoms of poisoning:
- massive and debilitating diarrhoea
- motor impairment
- change in muscle tonus
- convulsion - in case of severe poisoning
First aid:
- call a veterinarian as soon as possible
Pheasant's eye, spring pheasant's eye, yellow pheasant's eye, false hellebore
(l. Adonis vernalis)
source: luirig.altervista.org
Can be found in forests and moors. The whole plant is poisonous, it contains glycosides which affect the heart. It destroys liver and cardiac muscle, as well as causes inflammation of digestive tract.
Symptoms of poisoning:
- colic symptoms
- increased heart rate
First aid:
- immediately call a vet - lethal dose for the horse is as little as 25 g of dry lupin!
Foxglove, common foxglove, purple foxglove, lady's glove
(l. Digitalis purpurea)
source: shutterstock.com
It usually can be found on the skirts of forests, but it is also common as an ornamental plant. All the plant's parts contain glycosides, including: digitoxin, digoxin, which affect the heart. Big dose lead to respiratory functions, circulatory system impairment and cardiac arrest. The poisoning usually takes place while giving the horse hay, which contains dried foxglove. 25 g of dried leaves is a deadly dose.
Symptoms of poisoning:
- at first: excessive sweating and motor activation
- mucosa irritation
- cardiac and circulatory system disorders
- later: convulsion, spasms and colic symptoms
First aid:
- administering activated carbon
- calling a veterinarian, who would administer drugs that will stabilise the horse's cardiac functions
Oleander
(l. Nerium oleander)
source: commons.wikimedia.org
Often found as a garden or pot plant. Whole oleander contains poisonous and strong glycosides causing cardiorespiratory failure.
Symptoms of poisoning:
- diarrhoea
- cardiac disorders
- colic symptoms
- rapid decrease of body temperature
- hyperactivity
First aid:
- immediately call a veterinarian!
- it is one of the most dangerous plants for horses, it kill the horse off within 24 hours from ingestion
Eastern black walnut
(l. Juglans nigra)
This plant comes from USA, but it is becoming more popular in central Europe, planted as an ornamental tree. Not only their leaves are harmful to horses. Sometimes its sawdust is also toxic. Which is why you should pay attention to the source of your horse's bedding.
Symptoms of Eastern black walnut leaves poisoning:
- increased heart rate
- fever
- limbs swelling
- acute laminitis
Symptoms of contact with Eastern black walnut sawdust:
- beginning after 24 hours
- allergic reaction
First aid:
- isolate the horse from poisonous sawdust, wash his limbs with cold water and change the bedding in his stall
- in the case of food poisoning you have to immediately call a vet
Larkspur
(l. Delphinium)
source: 1zoom.net
The whole plant is poisonous. Symptoms begin very soon after consumption.
Symptoms of poisoning:
- initially: severe hyperactivity
- lack of movement coordination
- stumbling
- flatulence
- heart arrhythmia
- breathing difficulties
- excessive salivation
- later: difficulty in moving, paralysis, convulsions, which precede the horse's death
First aid:
- call a veterinarian as soon as possible - the treatment should be symptomatic
Bracken, brake, common bracken, eagle fern
(l. Pteridium aquilinum)
source: lookfordiagnosis.com
Often found in forests or on their skirts, sometimes planted as an ornamental plant. Both fresh leaves and stems, as well as dried and given in hay are poisonous to horses. Eating bracken does not give symptoms right after consumption. However, its regular ingestion becomes dangerous, then poisoning symptoms might show after 1-2 months, emaciating the horse's organism.
Symptoms of poisoning:
- weight loss
- difficulties with moving
- spine curves up in a shape of an arc
- heart arrhythmia - initially slower heart rate, then arrhythmia
- apathy
- reluctance to work
- hyperactivity
- excessive sensitivity to touch
- bloodstained diarrhoea
- blood in the urine
First aid:
- the animal usually dies after approximately 10 days from the appearance of first symptoms of poisoning, which is why you should have time to call a veterinarian, who can try administering thiamine, which - unfortunately - not always have the desired effect
Belladonna, deadly nightshade
(l. Atropa belladonna)
source: henriettes-herb.com
Whole plant is toxic, but the biggest threat are fruits. Black shiny berries in the size of cherries consist of highly influential alkaloids. 120-180 g of dry mass is a lethal dose.
Symptoms of poisoning:
- increased heart rate
- anxiousness
- increased number of breaths
- constipation
- colic
- increased thirst
- vision disorders
- dilated pupils
- bowels paralysis
- later: severe convulsions, paralysis, excessive sweating
- stumbling
- balance and breathing difficulties
First aid:
- calling a vet is necessary
Hoary alyssum, false hoary madwort, hoary berteroa, hoary alison
(l. Berteroa incana)
source: wildflowerchild.info
Whole plant is poisonous, even dried. Symptoms of poisoning shows when the horse eats as much hoary as 25% of the fodder he consumed. First symptoms show after 1-2 days from ingesting the plant.
Symptoms of poisoning:
- limbs swelling
- laminitis
- fever
- apathy
- reluctance to eat and drink
- later: dehydration and colic symptoms
First aid:
- you should call a vet, who would give the horse symptomatic treatment, with emphasis on fluid therapy
- it is crucial to prevent development of laminitis, which might transform into a chronic form
- there is a risk of the animal's death due to dehydration and heart failure
Castorbean, castor-oil-plant
(l. Ricinus communis)
source: bananaridge.com
Ornamental plant coming from Africa. Its seeds contain strongly influential glycoproteins belonging to the most dangerous poisonous plant compounds (for example ricin). Even little amount ingested by a horse causes poisoning.
Symptoms of poisoning:
- apathy
- consciousness disorder
- motor coordination disorder
- difficulties with standing on the horse's legs
- massive diarrhoea
- bowel contractions
- weak and slow heart rate
- paralysis of neck muscles
- convulsion
First aid:
- you should give the horse a lot of fluids
- it is worth administering activated carbon
- it is necessary to call a vet, who will administer anticonvulsants and other drugs
Rhododendron, rhodies
(l. Rhododendron)
source: pixabay.com
The most harmful are: nectar, leaves and flowers. It the latter two, rhododendron contains diterpenes causing burning sensation in throat, and consumed in bigger amounts causes stomach and bowel contractions, as well as weakening breathing functions.
Symptoms of poisoning:
- breathing disorders
- excessive salivation
- reflux
- diarrhoea
- weakening of muscles functioning and tension
- slow heart rate
First aid:
- administer activated carbon and purge as soon as possible in order to precipitate elimination of toxins from the organism
Field horsetail, common horsetail/water horsetail
(l. Equisetum arvense/Equisetum fluviatile)
source: alamy.com
All this plant's parts consist poisonous alkaloids (for example nicotine), big amounts of silica, saponin, flavonoids (including isoquercetin). Horsetail remains dangerous even after drying. Prolonged consumption of fodder containing horsetail becomes very harmful.
Symptoms of poisoning:
- loose stools
- shaky movements, stumbling - motor coordination disorders
- inertia
- muscles convulsions and paralysis
- croup dystaxia
- slow heart rate
- low body temperature
- weight loss
- hare's problem with becoming pregnant and bearing
- avitaminosis - lack of B1 vitamin
First aid:
- too late diagnosis of poisoning and lack of treatment might be fatal for the horse
- veterinarian should inject the horse with thiamin
Ragwort, common ragwort, stinking willie, tansy ragwort, benweed
(l. Jacobaea vulgaris)
author: David Nicholls, source: naturespot.org.uk
You can see this plant on roadsides, rubble, fallows and as a wild herb in gardens. It is the most common cause of poisoning on the British Islands. All ragwort's parts contain poisonous alkaloids, which are active even after the plant dries. If the horse constantly eats it (for example with his hay), it leads to serious liver damage. Symptoms might appear not earlier than after a few months.
Symptoms of poisoning:
- swelling
- jaundice
- emaciation
- attrition of the organism
- symptoms connected with dysfunctions of the nervous system
First aid:
- it is necessary to diagnose the poisoning as soon as possible and contacting a vet
Hemlock, poison hemlock
(l. Conium maculatum)
source: wnmu.edu
This plant can be found on damp rubble, thickets by walls, as well as on wastes and fallows. All hemlock's parts contain poisonous alkaloids (for example coniine), which give burning sensations in the oral cavity after eating them. Roots are the most poisonous during early spring, later overground spring is more harmful.
NOTE! Hemlock is frequently mistaken for parsley and parsnip, as all the three plants look alike in the first stage of growth.
Symptoms of poisoning:
- weakening of muscles
- advancing paralysis that begins from legs
First aid:
- activated carbon + calling a vet
Aconite, monkshood, wolf's bane, leopard's bane, mousebane, women's bane, devil's helmet, Queen of all Poisons, blue rocket
(l. Aconitum)
source: megacentregroupe.com
The whole plant is poisonous, because all its parts contains highly toxic alkaloid - aconitine. It is the most poisonous strain in Poland. As little as 10-12 g is lethal for horses.
Symptoms of poisoning:
- initially: hyperactivity
- digestive system disorders - colic, diarrhoea
- inflammation of stomach mucosa
- frequently: permanent kidneys damage
- if the horse consumed big amount: cardiac disorders, later death from cessation of breathing
First aid:
- activated carbon + necessarily call a veterinarian
Milkvetch, locoweed, goat's-thorn
(l. Astragalus)
source: nccih.nih.gov
Poisoning from eating this plant is very rare among horses. But sometimes it happens that this plant becomes their favorite snack, to which they even might get addicted.
Symptoms of poisoning:
- adynamia
- aggressiveness/excessive timidity
- constrained, unnatural motions
- impairment of sight and hearing - exaggerated reaction to stimuli
- with time: change of stool colour for darker
- convulsions
- miscarriages or bearing coals with severe birth defects
First aid:
- eliminating milkvetch from the horse's diet
- giving the horse high-quality insta-fodder
February daphne, mezereon, mezereum, spurge laurel, spurge olive
(l. Daphne mezereum)
from left: blooming, source: plantsystematics.org || ripe fruits, source: dpic.org
Most often found in forests, planted also as an ornamental shrub. All its parts, especially its rind and appealing, crimson fruits - 30 g is a lethal dose for horses.
Symptoms of poisoning:
- mucosa irritation
- colic symptoms
- suffocation
First aid:
- call a vet as soon as possible!
Spurge
(l. Euphorbia)
source: florafocus.wordpress.com
The whole plant is poisonous. Its milky juice contains poisonous substance - euforbon, which gives it a very unpleasant taste, but it also impairs digestive organs.
Symptoms of poisoning:
- skin irritation
- mucosa irritation
- enduring itching, the horse's constant scratching
- reluctance to eat
- watery eye
- conjunctival injection
- colic symptoms
- bloody diarrhoea
First aid:
- activated carbon + calling a vet
We, as horse owners, should be aware which plants are harmful to our horses' health, even lives. Remember to examine a pasture before you let your horse graze on it, so you can prevent him from eating a poisonous treat, which might turn out to be seriously harmful.
The same applies to hay - buy only from tested suppliers.
On the basis of the following books:
- Bruno P. Kremer "Rośliny trujące w domu, w ogrodzie, w naturze", publ. Multico, 1996
- Blendinger W. "ABC zdrowia konia", pp.93-95. Zrzeszenie Studentów Polskich, Zakład Treningowy Koni w Zbrosławicach, 1984
- Zwoliński J. "Hodowla koni", pp.342-344, publ. PWRiL Warszawa, 1983.
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