Horses Health - Toxic Plants Part 2

Plants That Can Seriously Damage Your Horses Health

As I said before, it’s lucky that horses don't find most poisonous plants very palatable. However, there are exceptions and sometimes horses will eat highly toxic or lethal doses of poisonous plants, even when forage is adequate. That's why summer is a good time to explore your horse pasture to be sure toxic plants are kept out of your horse's diet.

This issue will cover:

• Water Hemlock
• Ground Ivy
• Larkspur (Delphinium)
• Bracken Fern
• Horsetail
• Caster Oil Bean
• Red Maple
  
• Buckwheat
• Alsike Clover
• Rhododendron and Relatives
• Potato and Tobacco Leaf Plants

This is the same reminder I gave last time. You need to know that I have not written the following – I am not a Vet or a plants man, so I have copied this information simply to make it easy for you to read. I would not re-write it because I was afraid of getting something wrong that may prove fatal to your horse, so I make no apologies for copying this.

Water Hemlock
All parts of the water hemlock plant, also known as western water hemlock, contain a toxin called cicutoxin. Some consider this to be one of the most poisonous plants in the US. Frequenting moist areas such as wet meadows and pastures or the banks of ponds or streams, it resembles the larger poison hemlock, but only reaches a height of two to three feet. Tuberous roots and immature shoots and leaves are particularly toxic and only a small amount is needed to poison a horse. The plant seems more attractive to horses after being sprayed with the herbicide 2,4-D. Common names include false parsley, snakeroot and poison parsnip. Symptoms include muscle tremors which can develop into violent convulsions and respiratory shutdown. Early signs such as excessive salivation and frothing may occur as quickly as 15 minutes after ingestion. Convulsions can be extremely severe, with head and neck thrown back, legs flexed as if running and abdominal pain is generally present accompanied by an associative grinding of teeth. Coma and death usually follow and there is no known treatment. The toxins act quickly and horses are rarely saved, however horses which make it through the first five to six hours after the onset of symptoms have a good chance of survival.

Ground Ivy
Ground ivy, commonly called Creeping Charlie, is present throughoutmuch of North America. Horses must ingest relatively large amounts for fatal consequences to occur, and such events are commonly traced to the plant being baled into the horse's feed. When ground ivy is present or suspected, consider unusually severe sweating accompanied by frothing at the mouth and / or difficulty breathing as signs of potential ground ivy poisoning.

Larkspur (Delphinium)
In the Western US, larkspur is the number two cause of livestock losses. Under natural conditions, horses will sample larkspur but will not eat enough to kill themselves if other feed is available. Delphiniums planted in ornamental gardens should be considered as toxic as their wild counterparts and the same precautions should be taken as with oleander.

Bracken Fern
This plant, also known as the brake fern, is common in wooded areasof the Pacific Northwest. Horses generally avoid it, but some can acquire a taste for it. Toxicity is cumulative and generally symptoms appear after the horse nibbles on this plant repeatedly over a long period of time. Early symptoms include weight loss which can progress to unsteady walking, then staggering with the horse spreading with all four feet to stay balanced, often pressing his head into solid objects. If untreated, death will occur from several days to several weeks after the symptoms appear.

Horsetail
Horsetail, also called mare's tail and scouring rush, poisons the horse in a similar fashion as bracken fern. All varieties of Horsetail are poisonous and they are often found near bogs and streams. The only reported difference in symptoms from bracken fern poisoning is that with Horsetail the animal may become quiet, unresponsive or comatose prior to death.

Castor Oil Bean
The castor oil plant, or palma christi, is grown as an ornamental plant in California and many southern states. It contains ricin, which causes severe irritation to the intestinal tract. (Castor oil is non-toxic because ricin is not soluble in oil.) The seed is the part of the plant which is poisonous - to all animals. As little as 7 grams of seeds have been reported to kill a horse although it is generally considered that about 50 grams (about 150 beans) are necessary to kill a healthy 1000 lb. specimen. Symptoms may not appear until two to three days after ingesting the beans. When signs do appear they are generally acute and progress rapidly. The animal may actdoped up and lose coordination, followed by profuse sweating. Signs of shock are not uncommon. Neck and shoulder spasms may appear accompanied by an extremely profound but ineffective heartbeat which can be easily felt, but which produces a weak and rapid pulse. Early on a temperature may be present up to 107 degrees F (41.5 C). Eventually a profuse, watery diarrhea appears often accompanied by colic-like pain. Finally the horse may go into convulsions and die.

Red Maple
Red Maples are natives in the eastern US and can be found as ornamental specimen trees in many other areas. The dried leaves and bark of the red maple can produce significant anemia in the horse when eaten. Symptoms include general weakness, and increased respiratory and cardiac rates indicating the animal's attempt to compensate for the anemic condition. Please note: Some nurseries have crossed silver maples with red maples to produce more color. These hybrids are also toxic to horses. Check with your nurseryman to make sure you are planting true silver maples!

Buckwheat
Buckwheat contains a pigment called fagopyrin, which when ingested by the horse, causes photosensitive dermatitis. Symptoms include a weepy, itching dermatitis in those areas exposed to sunlight.

Alsike Clover
Hormones in this plant can cause photosensitization of the skin and hypertrophy of the liver (big liver disease). Visible symptoms include increased sensitivity of the skin (especially the nose and lips) to sunlight.

Rhododendrons and relatives
These plants, along with azaleas, laurels and mountain pieris contain grayanotoxin. Symptoms include an excess of green, frothy salivation which is generally associated with gastrointestinal irritation and colic.

Potato and Tobacco Leaf Poisoning
Nicotine and its related compounds are toxic to horses. The stems and leaves of many types of potato plants contain high concentrations of this alkaloid, as do the wild varieties of tobacco which grow in the western United States and Hawaii. Horses have also been known to be poisoned by domestic tobacco which has been harvested and within their reach, typically when stored in barns where they are stabled.
Nicotine affects the autonomic nervous system. In minor cases the horse may shake, shiver or twitch, particularly around the neck and shoulders. As the symptoms advance, staggering, prostration and paralysis may be evident. The heart may beat violently but produce a weak, rapid pulse. The horse may show an elevated temperature, yet the extremities will feel cold. Sometimes colic and / or labored breathing may be present.
Severe cases will usually produce a rapid onset of symptoms, followed a few minutes later by death, although some horses have been known to struggle with nicotine effects for up to several days. There is no known treatment for nicotine poisoning.

From the author:
Roger Bourdon has written a book on Introduction To Horsebackriding and Horse's Health. (Article Adapted by All About Horses)

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