As fall foliage emerges, many equestrians are excited by the break in the heat and the reduction of the pesky insects. However, the fall also brings an increased risk of horses consuming dropped leaves as the summer pasture and lush forage departs for the season. While many types of these leaves are safe for your horse to eat (in small amounts), sometimes specific fallen leaves, bark, and tree debris can be poisonous to your horse. This is particularly true in the case of red maple trees, black walnut trees, cherry trees, plum trees, and oak trees. In this blog post, we take a look at red maples and acorn poisoning so you understand how to protect your horse and how to diagnose these toxicities.
Red Maple Poisoning
Cautioned against in all equestrian circles, red maple trees are one of the biggest dangers in the fall months. Red maple trees grow primarily in the northeast United States and Canada. When consumed, the wilted or dried leaves of the red maple tree can severely damage the red blood cells of the horse, which limits their oxygen-carrying abilities.
“Toxicity typically occurs in the fall during normal leaf drop and when pastures tend to have less available forage,” explains Tom Guthrie, a statewide Equine Extension Educator for Michigan State University (MSU). “However, other factors such as frost, tree trimming, and storm damage may also contribute to wilted leaves.” The fresh red maple leaves are not as toxic, however, consumption should still be discouraged as you do not want your horse to acquire a taste for leaves.
Red Maple Toxicity shows a variety of symptoms, with the most common being depression, reduced appetite, lethargy, dark reddish to deep brown-colored urine, an increased respiratory rate, and an increased heart rate. As the toxicity progresses, the horse’s breathing becomes increasingly labored and may lead to death.
When caught early, veterinary invention can help reverse the effects of the toxins. “Activated charcoal followed by mineral oil may be given soon after the horse eats leaves,” says Tom. In many cases, fluids and blood transfusions are needed to flush the horse’s system and provide them with red blood cells. Vitamin C, non-steroidal anti-inflammatory drugs, and corticosteroids are also treatment options that your veterinarian may employ.
It only takes a limited amount of leaves to be detrimental to your horse’s health. “A 1,000 lb horse would need to ingest approximately 1.5 lb of leaves for toxicity to be seen,” Tom explains. “Additionally, approximately 3 lb of ingested wilted or dry leaves could be lethal. Small equine like ponies and donkeys can show toxicity symptoms after ingesting as little as 0.5 lb of maple leaves.”
It is estimated the red maple leaves are only toxic for four weeks after they fall from the tree. This is welcome news for many horse owners, especially because it ensures that the pasture will be safe the following spring. The best way to deter red maple poisoning is to provide your horse with adequate amounts of high quality forage whenever possible. Most horses will choose not to eat the leaves, provided they are receiving their nutritional requirements in pasture and hay.
Oak Acorn Poisoning
While many equestrians are aware of the dangers of red oak trees, the oak trees and acorns can also be detrimental to your horse’s health. Although more frequently seen in cows and sheep, horses can suffer from acorn toxicity or acorn poisoning. In the fall, oak trees produce acorns and shed their leaves in preparation for the winter months. Because oak trees tend to be common in horse’s pastures and feeding areas, acorn poisoning can occur if a horse ingests large quantities of oak bark, oak leaves, or acorns.
You may be asking, “What is acorn poisoning?”, the fact is, it is really quite simple. Oak leaves, oak bark, and acorns all contain high levels of gallotannins; these gallotannins are broken down in toxins within the body during the digestive process. If your horse consumes large amounts of these toxins, it can damage the stomach and intestinal lining, blood vessels, and kidneys.
The symptoms of acorn poisoning are varied, but they often include fever, difficulty in defecation, diarrhea, or urine which appears bloody; this is due to the damage of the digestive tract and kidneys. Typically, acorn poisoning leads to horses colicking. However, in cases of slight acorn poisoning, the horse may only present with lethargy or a reduced appetite.
If you think that your horse has ingested copious amounts of acorns and oak leaves, the best course of action is to call your vet. According to Dr. Alisha Gruntman, an internist at the Hospital for Large Animals at Cummings Veterinary Medical Center, in Medford, MA, “Treatment is aimed at correcting dehydration and electrolyte abnormalities, controlling gastrointestinal pain, and supporting kidney and intestinal function.” In extreme cases, the damage to the horse’s system is too severe and the condition is fatal.
“Keeping palatable forage sources such as grass or hay available when horses are turned out around oak trees will keep most horses from eating oak leaves, blossoms, or acorns,” explains Dr. Gruntman. “If you have a horse that finds acorns or other parts of oak trees particularly tasty, you may have to move their turn-out area or fence off the oak tree to limit access. A horse ingesting the occasional acorn or leaf during grazing does not pose a risk of toxicity.”
While acorn poisoning is very rare and only occurs in a small percentage of horses that eat acorns or other oak by-products, it is still essential that you are aware of the possibility if you live in the Northeast where oak foliage is plentiful. If possible, remove your herd from pastures and paddocks with oak trees during the fall.
Black Walnut Trees
One of the most well-known poisonous tree species, Black Walnut trees can wreak havoc on your horse’s health and soundness. Typically, horses in the Northeast are exposed to black walnut heartwood through processed wood shavings as bedding, because the tree does not commonly grow this far north.
If your horse is exposed to black walnut wood or bark, as bedding or in another manner, they will most likely begin to exhibit signs of laminitis. According to Christina S. Cable, DVM, Dipl. ACVS, the owner of Early Winter Equine in Lansing, NY, “After exposure to black walnut shavings, a horse will usually begin to show the hallmark signs of laminitis within 10-12 hours. The lower legs of some horses will begin to swell, and they will be reluctant to move. Other horses might just shift their weight from one front foot to the other, or rock their weight backward. If asked to move, they will try to bear most of their weight on their heels instead of walking flat-footed. These are all classic signs of laminitis (except for the swollen legs). Other signs that might be present include a strong digital pulse and/or palpable heat within the hoof.”
If your horse begins to show signs of laminitis or you have another reason to suspect black walnut poisoning, you will need to act fast. Immediately remove your horse from their bedded stall and contact your veterinarian (an acute case of laminitis is always an emergency, no matter what the cause may be). With swift action, the prognosis for many horses is positive and recovery is possible.
It was once thought that all portions of the black walnut tree were poisonous to horses, including the leaves and walnuts, however new research suggests that it is only the heartwood and bark that carry the toxin. Regardless, it is recommended that you do not pasture your horse in an area with black walnut trees and ensure that you only purchase equine-grade bedding which is 100% free of black walnut wood.
Plum Trees, Peach Trees, and Cherry Trees
Some trees bear delicious fruit, but they can be disastrous to your horse’s health. Recent years more attention has been placed on the poisonous properties of the Prunus species of fruiting plants (mainly black cherry, chokecherry, fire cherry, peach, and plum trees). When the leaves from these trees drop, they begin to produce cyanide; the pits of the fruit also contain cyanide.
The cyanide from these trees will affect your horse in a matter of hours after ingestion. When the horse’s stomach acid breaks down the foreign matter, hydrogen cyanide is released and absorbed into the bloodstream. Cyanide poisoning prevents the cells of the body from properly absorbing oxygen, which causes the blood to turn bright red because the blood is overly oxygenated.
Symptoms of cyanide poisoning include heavy, distressed breathing, increased respiratory rates, and increased heart rates. “If found in time, the affected horse can be treated with chemicals that: 1) Remove the cyanide that is bound to the red blood cells and unblock cellular oxygen transport, and 2) replenish natural stores of a compound that can bind the remaining cyanide and render it harmless,” explains Dr. Cable.
For farms that need to utilize areas with trees overhead, try to rake under the trees daily and remove leaves and acorns; you will also want to ensure that your horse has adequate amounts of forage so that they are not scavenging for additional vegetation. With a bit of knowledge and due diligence, you can prevent tree-related toxicity and poisoning from happening to your horse.
At The Cheshire Horse, we care about the health and wellness of our customers’ horses. If you have any equine-related questions or would like to talk about the horse health supplies that we carry, we encourage you to speak with a member of our friendly and horse-loving sales staff.
Please note: This blog post is meant for informational purposes only and is not intended to replace veterinary care. If you suspect red oak poisoning, cyanide poisoning, black walnut poisoning, or acorn toxicity or have another equine health concern, we recommend that you reach out to your veterinarian or horse health professional immediately.