Month: July 2022

Which plants are most toxic to horses? In this series of posts, I continue to describe the most common plants that are toxic to horses. Here we look at the Hemlock.

Description:

Hemlock (Conium Maculatum) is an erect, branched biennial plant. It can reach 2m in height. It is common in waste ground, in ditches, and by roadsides. It is common in Europe, but rare in West and Central Scotland. In the US, Hemlock is also known as Musquash Root and Spotted Cowbane. These plants are considered amongst the most toxic of plants, and a deadly poison. One mouthful can apparently kill an animal in 15 minutes.

What the herbalist says:

The herbalist Culpeper tells us that: the common great Hemlock grows up with a green stalk, four or five feet high, or more, full of red spots sometimes, and at the joints very large winged leaves one set against the other, dented about the edges, of a sad green colour branched towards the top, where it is full of umbels of white flowers, and afterwards with whitish flat seed; the root is long, white, and sometimes crooked, and hollow within. The whole plant, and every part, has a 1trong, heady, and ill-favoured acent. It grows by walls and hedges throughout all parts of this country. It flowers and seeds in July, or thereabout. Saturn claims dominion over this herb. Hemlock is exceedingly cold, and very dan­gorous, especially to be taken inwardly. It may safely be applied to inflammations, tumults, and swellings in any part of the body, as also to St, Anthony’s fire, wheals, pushes, and creeping ulcers that arise of hot sharp hu­mours, by cooling and repelling the heat; the leaves bruised and laid to the brow or forehead, are good for red and 1wollen eyes; as also to take away a pin and web grow­ing there; take a small handful of this herb, and half aa much bay-salt, beat together, and applied to the contrary wrist of the hand, removes it in two applications. The root roasted and applied to the hands, helps the gout.

The active agents:

The poisonous agents in Hemlock are alkaloids, and these can be extremely toxic. They are more concentrated in the stem and leaves than the root, apparently. Paralysis and convulsions may result from ingesting Hemlock. Hemlock is best known in human history as the poison that was handed to Socrates in 399 BC.

Herbal Medicine

In herbal medicine, Hemlock has been used as a sedative and for cough relief in bronchitis.

Poisoning with Hemlock?

Horse DVM, offers some interesting insights. Hemlock was native to Europe and western Asia. It was however introduced into North America in the 1800s as an ornamental. It then escaped cultivation. It is now widely distributed across much of the United States. It is present in Canada too. As a biennial, poison hemlock produces leaves as a basal rosette in year one. This develops into an upright flower stalk during year two.

Poison hemlock contains eight piperidine alkaloids. Y-coniceine and coniine are the most abundant. These two are the predominant cause of acute and chronic toxicity in horses. Coniine is similar in structure and function to nicotine. These toxins have a direct effect on the horse’s nervous system.

Whilst all parts of the plant are toxic, the most toxic parts are the fruits when they are still green, and stems.

The best way is to remove Hemlock is before seed production. If you are hand-pulling, wear gloves as the plant is highly poisonous. If Hemlock is growing freely on your land, remove it, safely. Please ensure that your horses cannot come into contact with this deadly herb.

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I hope this article has been helpful. Other articles about plants toxic to horses appear on my blog and are linked to my Professional Facebook Page. If there is a plant that you would like me to write about, please get in touch via Contacts.

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Bibliography:
Keith Allison: A guide to Plants Poisonous to Horses. J.A. Allen. Revised edition, 2011.
John Gerarde: The Herball or General Historie of Plantes, 1636.
Culpeper: Index Of Herbs By Nich. Culpeper, Gent. Student in Physick and Astrologie, 1616, 1654
Sandra McQuinn: Horse owner’s Guide to Toxic Plants. Skyehorse Publishing. 1996, 2020.

Which plants are most toxic to horses? In this series of posts, I continue to describe the most common plants that are toxic to horses. Here we look at the mighty Oak.

Description:

Oak (Quercus spp.) is a tree, native to Britain, and commonly found in woodland, parkland, and near pastures. Oak is also widespread across North America. The oak may live for hundreds of years. Trees often have their lower branches lopped, which reduces the life of the tree. In the normal cycle, the Oak puts out lower branches which then support the tree in later life. Without these lower limbs, the tree can end up splitting. Farmers often cut the lower branches so they can plough around the tree. This may plough more of the field. But it compacts the soil around the surface roots and also does the tree no favours.

Many Oaks in Britain are now over 500 years old. Many have seen history roll by, since the time of the Wars of the Roses, and even before. In her book “Wilding“, Isabella Tree describes how Ted Green (custodian of the Oaks in Royal Windsor Park) talked of the life history of the tree. “The Oak grows for the first 300 years. Rests for another 300 years. And then spends the last 300 gracefully declining”. 900 years. It really makes one think! Back in the 17th Century, the Herbalist Culpeper wrote of the Oak.

What the herbalist says:

The herbalist Culpeper tells us that: This tree grows to a vast height, spreading out into innumerable and irregular branches. The leaves are oblong, obtuse, deeply sinulated, and of a dark green. The flowers are both barren and fertile on the same tree ; the former are collected into loose catkins ; the latter are seat­ ed in the buds, and both sorts are small and inconsiderable, The seed is oval-formed, of a leather-like coat, which ap­pears as if rasped at the base, and is fixed to a short cup. It is too common to require a particular spec1fi­cation of the place of its growth. The flowers appear in April, and the acorns are ripe in October and November. Jupiter owns the tree. The leaves and bark, and the acorn cups, bind and dry much. The inner bark and the thin skin that covers the acorn, are used to stay the spitting of blood, and the flux.

The active agents:

The poisonous agents in Oak are the tannins, and these can be extremely toxic. Nonetheless, information on the toxicity of oak appears confusing. On the one hand, some horses have apparently died from Oak poisoning. On the other, there exist reports of horses eating acorns with little or no ill effect. In my own experience, I have seen certain horses of a herd enjoying fallen acorns. Others will graze around them. No member of that herd suffered any consequence in the three years I managed them.

Herbal Medicine

In herbal medicine, Quercus has been used as an astringent and an antiseptic.

Poisoning with Oak?

Cynthia Gaskill, American Board of Veterinary Toxicology, has written about the Oak. She explains that acorn poisoning has been well documented in cattle. Very few cases have been confirmed in horses (in the US). Symptoms of acorn toxicity include depression and loss of appetite. There may be digestive-tract issues: colic, gastric upset and diarrhoea (often bloody). Kidney and possibly liver damage are possible. The more acute the symptoms, the higher the likelihood of death. Horses that experience a gradual onset of symptoms are more likely to survive.

In November 2013, a large number of horses apparently died in the New Forest, in the UK. An article in Horse and Hound states that 31 ponies roaming on the New Forest died, along with 12 cattle. In a normal year, many fewer animals are affected each autumn. 2013 was what is known as a “mast” year, when oaks and apple trees produced plenty of fruit. As such, extreme prudence is necessary.

As with many toxic plants, horses are more likely to eat them if they do not have enough grass or hay. Imagine several horses are being kept underfed. An oak tree in the paddock drops a large number of acorns. It is possible that some of the horses might now eat a large number of acorns to supplement their food.

It is important to note that the amount of Tannins varies during the year and season. As such it is difficult to predict how toxic the leaves/acorns might be. If you have an oak in your pasture, the best strategy would be to fence it off. This ensures that it will be out of grazing range for the herd.

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I hope this article has been helpful. Other articles about plants toxic to horses appear on my Professional Facebook Page. If there is a plant that you would like me to write about, please get in touch via Contacts.

Quarterly Holistic Newsletter

If you have enjoyed this article, please keep in touch and sign up for our Quarterly Holistic Newsletter.

Bibliography:
Isabella Tree: Wilding – The return of nature to a British Farm. Picador, 2018.
Keith Allison: A guide to Plants Poisonous to Horses. J.A. Allen. Revised edition, 2011.
John Gerarde: The Herball or General Historie of Plantes, 1636.
Culpeper: Index Of Herbs By Nich. Culpeper, Gent. Student in Physick and Astrologie, 1616, 1654
Cynthia Gaskill: Are acorns poisonous to horses?
Horse and Hound: A huge rise in equine deaths due to acorns.

Which plants are most toxic to horses? In this series of posts, I continue to describe the most common plants that are toxic to horses.

Description:

Foxglove (Digitalis Purpurea) is a biennial plant that reaches about 1.5m in height. Its flowers are bell or helmet-shaped and they may be either purple or white.

What the herbalist says:

The herbalist Culpeper tells us that: This hath many long and broad Leaves lying upon the Ground dented about the edges, a little soft or woolly, and of a hoary green colour among which rise up somtimes sundry Stalks, but one very often bearing such Leavs thereon from the bottom to the middle, from whence to the top it is stored with large and long hollow reddish Purple Flowers, a little more long and eminent at the lower edg, with some white Spots within them, one above another, with small green Leaves at every one, but all of them turning their Heads one way and hanging downwards, having some threds also in the middle, from whence rise round Heads pointed sharp at the ends, wherein smal brown Seed lieth. The Roots are many smal Huskie Fibres, and some greater strings among them; The Flower hath no scent; but the Leavs have a bitter hot taste. Vertues and Use. This Herb is familiarly and frequently used by the Italians to heal any fresh or green Wound, the Leavs being but bruised and bound thereon; and the Juyce therof is also used in old Sores, to clens, dry, and heal them. The Decoction hereof made up with some Sugar or Honey is.

The active agents:

The poisonous agents in Foxglove are several. They are known as cardiac glycosides. These include digitalin, digitoxin, and several others. If ingested, abdominal pain, irregular pulse, tremors and convulsions may follow. Foxglove is not usually ingested by animals. It is easily avoided when growing in pasture, but more dangerous when it is incorporated in hay.

Herbal Medicine

In herbal medicine, Digitalis has been used in the treatment of internal bleeding, in inflammatory diseases, in epilepsy, and delerium tremens. Digitoxin is commonly used in heart medication for humans and horses but in tightly controlled doses.

Poisoning with Foxglove?

According to Simon Constables Equine Vets, these plants are thankfully unpalatable to horses and are rarely eaten as a fresh flower. If they are caught up in hay or haylage they can however be accidentally eaten. The effects on the heart increase the strength of heart contraction but slow conduction between the top (atrium) and bottom (ventricle) parts of the heart. This shift can lead to a fatal arrhythmia where the heartbeat becomes irregular. When the dose is sufficient, it may cause cardiac arrest. Treatments involve binding the digitoxin with activated charcoal. Oral liquid paraffin and fluids are given to reduce toxin absorption. If caught early enough, suitable drugs include atropine and lignocaine which help to reduce arrhythmia.

Whilst it is not suggested that the plant be removed from pastures (unless in great quantity), it is important to inspect hay/haylage. In this way, we can ensure that traces of Digitalis have not contaminated our horse’s staple.

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Other articles about plants appear on my Professional Facebook Page.
If there is a plant you would like me to write about, please get in touch via Contacts.

Quarterly Holistic Newsletter

If you have enjoyed this article, please keep in touch and sign up for our Quarterly Holistic Newsletter.

Bibliography:
Keith Allison: A guide to Plants Poisonous to Horses. J.A. Allen. Revised edition, 2011.
John Gerarde: The Herball or General Historie of Plantes, 1636.
Culpeper: Index Of Herbs By Nich. Culpeper, Gent. Student in Physick and Astrologie, 1616, 1654