Toxic Plants and How to Keep Your Horse Safe

As a horse owner, ensuring the safety of your equine companions is paramount. One of the most significant threats to your horses' well-being comes from toxic plants that may be lurking in their grazing areas. From common weeds to beautiful flowers, many plants can cause serious harm to horses if ingested. Understanding which plants are dangerous and how to identify them is crucial to keeping your horses healthy and thriving.
In this article, you'll learn about the seasonal risks associated with toxic plants and their impact on horse health. We'll explore how to create a safe grazing environment by identifying and removing harmful vegetation like nightshade, azalea, and oleander. You'll also discover the importance of recognizing trees poisonous to horses, such as oak trees, and how to handle emergencies related to plant poisoning. By the end, you'll have the knowledge to protect your horses from the hidden dangers in their pastures.
Seasonal Risks of Toxic PlantsAs a horse owner, you need to be aware that the risks from toxic plants change with the seasons. Each time of year brings its own set of hazards that you should watch out for to keep your horses safe.
Spring DangersSpring brings new growth and potential dangers. During this season, you should be particularly cautious of:

1. Rhododendron and Azalea: These ornamental plants can cause severe symptoms in horses, including vomiting, diarrhea, weakness, and even cardiovascular collapse [1].
   
2. Crocus: This spring flower can lead to excessive salivation, abdominal pain, and in severe cases, tremors and seizures [1].
   
3. Oleander: This common ornamental in the Southern United States can be deadly to horses. It affects the heart, potentially causing a decreased heart rate, abnormal rhythm, and even sudden death. Signs of poisoning can develop within 30 minutes to a few hours after exposure [2].
   

Summer HazardsAs summer progresses, new plants emerge, bringing different risks:

1. Red Maple Trees: While ingestion typically happens in fall, it can occur in summer if horses have access to wilted or dried leaves. Eating these leaves can damage red blood cells, leading to anemia. Symptoms can appear 12-48 hours after exposure, but may be delayed up to five days [2].
   
2. Yew: This evergreen plant, common throughout the United States, affects the heart and can cause rapid symptoms. Unfortunately, most affected horses are found already dead [2].
   
3. Hoary Alyssum: If your horse ingests this plant, you might notice swelling of their legs, fever, and laminitis. Symptoms can develop within 12-24 hours and last for several days [2].
   

Fall RisksFall brings its own set of challenges:

1. Box Elder Maple: The seeds from female box elder maple trees cause Seasonal Pasture Myopathy (SPM), which is 75-90% fatal. Symptoms include tremors, weakness, stiffness, dark urine, and rapid breathing, usually leading to death within 48 hours [3].
   
2. Red Maple: The risk of red maple poisoning increases in fall when horses have more access to fallen leaves [2].
   
3. Acorns from Oak Trees: While not mentioned in the provided excerpts, oak trees, which drop acorns in fall, can be toxic to horses if consumed in large quantities.
   

Winter ConcernsEven in winter, some plants pose a threat:

1. Japanese Yew: This evergreen shrub remains toxic year-round. About 0.1 percent of a horse's body weight in yew leaves can be lethal. Often, death occurs before treatment can be administered [4].
   
2. Dried Toxic Plants in Hay: During winter, when fresh forage is scarce, horses may be more likely to consume toxic plants mixed into hay [4].
   

To protect your horses year-round, it's crucial to identify and remove toxic plants from grazing areas. Remember, hundreds of poisonous plants grow in North America, and many are extremely common. As toxicologist Dr. Jeffery Hall states, "I defy anyone to tell me they have a pasture with zero poisonous plants" [5]. While horses generally avoid toxic plants when quality forage is available, it's best to eliminate these risks entirely. Be especially vigilant during times of scarcity or when introducing horses to new pastures.
Impact of Toxic Plants on Horse HealthAs a horse owner, you need to be aware of the various ways toxic plants can affect your equine companions' health. While horses are generally selective grazers, poisoning can occur when feed options are limited or when toxic plants are accidentally included in prepared feeds [6]. Understanding the impact on different body systems will help you recognize potential issues and take prompt action.
Digestive SystemMany toxic plants primarily affect the gastrointestinal tract of horses. When ingested, these plants can cause a range of symptoms, including:

1. Colic and abdominal pain
2. Diarrhea or constipation
3. Loss of appetite
4. Excessive salivation

For example, nightshade species can lead to colic, diarrhea, and even intestinal impaction [3]. Similarly, oak poisoning can cause intestinal stasis, with feces initially becoming hard and dark, followed by black tarry diarrhea [7].
Nervous SystemNeurotoxic plants can have severe effects on a horse's central nervous system. These plants are often palatable, making them particularly dangerous [6]. Common symptoms of nervous system toxicity include:

1. Ataxia (loss of coordination)
2. Muscle tremors
3. Depression or hyperexcitability
4. Seizures

For instance, locoweed poisoning can result in depression, reluctance to move, and intention tremors [6]. Yellow starthistle and Russian knapweed can cause a condition known as "chewing disease," where horses chew but can't swallow due to facial and throat nerve dysfunction [6].
Cardiovascular SystemSome toxic plants have a direct impact on the horse's heart and circulatory system. These effects can be particularly dangerous and may lead to sudden death. Signs of cardiovascular toxicity may include:

1. Irregular heartbeats
2. Weak pulse
3. Labored breathing

Oleander, for example, can cause severe cardiovascular issues. Even a small amount can be lethal, with symptoms appearing within hours of ingestion. These may include irregular heartbeats and a weak pulse [7].
Reproductive SystemCertain toxic plants can have devastating effects on a horse's reproductive health. These impacts can range from infertility to severe birth defects. Key issues include:

1. Abortions
2. Birth of weak foals
3. Fetal deformities

Lupine consumption, for instance, can lead to serious reproductive failure in horses. Common fetal deformities resulting from lupine toxicity include twisted and deformed limbs due to contracted flexor tendons and abnormal bone and joint development [7].
It's crucial to remember that the effects of toxic plants can vary widely. Some plants, like milkweed, can affect multiple body systems simultaneously, causing respiratory difficulties, digestive issues, and nervous system problems [3] [7]. Additionally, the impact of some toxic plants may not be immediately apparent. For example, plants containing pyrrolizidine alkaloids can cause liver damage that only becomes evident weeks or months after ingestion [7].
To protect your horses, it's essential to know your pasture and research the plants growing in and around your horses' living areas [8]. Always inspect hay for weeds, as many retain their toxicity even when dried [8]. If you suspect your horse has ingested a toxic plant, contact your veterinarian immediately for proper diagnosis and treatment.
Creating a Safe Grazing EnvironmentPlant Identification TechniquesTo keep your horses safe, you need to know what's growing in your pastures. Learning to identify plants is crucial for maintaining a healthy grazing environment. You can use various tools to help with this task. One useful app is Seek, which can identify plants in real-time. It allows you to take pictures and save observations on your phone, providing information such as taxonomy and whether the plant is native or introduced [9].
Regular inspections of your pastures and fence lines are essential. This helps you spot and remove any unwanted plants before they become a problem. Remember, seeds can be carried into pastures by wind, birds, and other wildlife, leading to new growth of potentially toxic plants [10].
Safe vs. Toxic Plant AlternativesWhen creating a safe grazing environment, it's important to promote the growth of nutritious grasses while eliminating toxic plants. Grass species can be divided into warm-season and cool-season varieties. In the transition zone, which includes Kentucky and neighboring states, cool-season grasses are the primary pasture grasses, although both types can be maintained [11].
When selecting grass species, consider the intended use of the pasture. For example, bermudagrass might be recommended for a pasture that gets heavy use only in summer months due to its high yield and grazing tolerance [11].
Be cautious with tall fescue, as it can be toxic endophyte-infected (also known as "KY31" or "KY31+"). This type can be problematic for livestock, especially late-term broodmares. Instead, consider novel endophyte tall fescue, which offers persistence without the toxicity issues [11].
Rotational GrazingImplementing a rotational grazing system can significantly improve pasture health and reduce the risk of toxic plant consumption. This sustainable practice involves frequently rotating livestock to different portions of a pasture to minimize overgrazing [12].
Rotational grazing offers several benefits:

1. Improved pasture quality and fertility
2. Increased forage harvested per acre (up to 2 tons dry matter per acre more than continuous grazing) [13]
3. Better weed control
4. More even manure distribution
5. Enhanced soil health and structure

While rotational grazing typically has higher upfront costs due to the need for more fencing and water systems, it offers long-term economic benefits. These include healthier herds, reduced maintenance and fertilizer costs, and greater pasture productivity [12].
Water Source ManagementProper water management is crucial for creating a safe grazing environment. You can improve water quality by restricting where livestock are able to graze. For example, installing fences to prevent horses from entering streams, rivers, and lakes can help restore stream banks and improve water quality by preventing the influx of excess nutrients [12].
Remember, good pasture management is essential for promoting the growth of healthy grasses and avoiding the proliferation of weeds. This includes practices such as soil testing, liming and fertilizing, grazing management, mowing, and chemical weed control as needed [10].
By implementing these strategies, you can create a safer, more nutritious grazing environment for your horses while promoting sustainable pasture management.
Emergency Response to Plant PoisoningFirst Aid MeasuresIf you suspect your horse has ingested a toxic plant, it's crucial to act quickly. Your first step should be to remove your horse from the source of poisoning [14]. Take your horse to a safe, shaded area and provide plenty of clean water and hay that doesn't contain toxic plants [15]. Avoid stressing the animal, as this can exacerbate the effects of poisoning.
If your horse's skin or fur is contaminated, wash it gently with mild shampoo and water, then rinse thoroughly and dry [14]. Keep your horse isolated from other animals to prevent cross-contamination [14].
Contacting a VeterinarianImmediately after taking initial precautions, contact your veterinarian. Time is critical in cases of plant poisoning, and any delay can significantly reduce your horse's chances of recovery or survival [16]. When you call, provide as much information as possible about the incident, including where and how it happened [14].
If you're unable to reach your regular vet, you have other options. The ASPCA Animal Poison Control Center (APCC) is available 24/7, 365 days a year at (888) 426-4435 [17]. Alternatively, the National Animal Poison Control Center offers a toll-free animal poison hotline at 1-800-548-2423 [16]. These services may charge a consultation fee, but they can provide valuable advice for treating suspected poisoning cases.
Collecting Plant SamplesTo help your veterinarian identify the toxic plant and choose appropriate treatments, try to collect a sample of the suspected plant. Wear gloves and protective clothing when doing this [15]. Place the plant material in a sealed plastic bag with a dry paper towel [15]. If you can't safely collect a sample, carefully take photos of the plant instead.
Follow-up CareAfter the immediate crisis, focus on preventing future incidents. Develop a plan to remove toxic plants from your pasture or to purchase new hay [15]. Take note of pastures or hay that may contain toxic plants and use Integrated Pest Management (IPM) tools to prevent future exposure [15].
Remember that dead or wilting plants may still be toxic. Plants treated with herbicides or hand-pulled may be more enticing to horses due to biochemical changes, so remove these plants or relocate your livestock [15].
Regular pasture management is key to preventing plant poisonings. This includes weed removal and familiarizing yourself with common poisonous plants in your area [18]. Be particularly vigilant about fence rows, which often harbor potentially poisonous plants [18].
By staying informed and taking prompt action, you can significantly improve the outcome for your horse in case of plant poisoning. Always prioritize prevention and maintain a safe grazing environment to keep your horses healthy and thriving.
ConclusionProtecting horses from toxic plants is a crucial aspect of responsible horse ownership. By understanding the seasonal risks, recognizing the impact on horse health, creating safe grazing environments, and knowing how to respond to emergencies, horse owners can significantly reduce the chances of plant-related health issues. This knowledge empowers owners to take proactive steps to ensure their horses' well-being and to act swiftly if poisoning occurs.
Ultimately, the key to keeping horses safe from toxic plants lies in ongoing vigilance and education. Regular pasture checks, proper plant identification, and smart grazing management are essential to minimize risks. By staying informed about local toxic plants and maintaining open communication with veterinarians, horse owners can create a safer, healthier environment for their equine companions. This approach not only protects horses but also gives peace of mind to their caretakers.
FAQs1. How can I stop my horse from consuming toxic plants?
To prevent horses from eating poisonous plants, ensure they have access to high-quality forage. Horses typically avoid toxic plants if they have plenty of good forage. However, during droughts or if the pasture is overgrazed, horses might start to eat less desirable plants available to them.
2. Which plant is the deadliest to horses?
The most dangerous plants for horses include:

• Bracken fern (Pteridum aquilinum)
• Hemlock (Conium maculatum)
• Tansy ragwort (Senecio spp.)
• Johnsongrass/Sudan grass (Sorghum spp.)
• Locoweed (Astragalus spp. or Oxytropis spp.)
• Oleander (Nerium oleander)
• Red maple trees (Acer rubrum)
• Water hemlock (Cicuta spp.)

3. What are some plants that are safe for horses?
Plants that are non-toxic and safe for horses include:

• Black Eyed Susan
• Sage
• Marigold
• Cornflowers
• Snapdragons

4. Why might horses ingest poisonous plants?
Horses generally avoid poisonous plants as they find them unpalatable. However, if the available grass or hay is insufficient, especially in overgrazed or drought-affected areas, horses may resort to eating toxic plants as they might be the only option available.
References[1] - https://extension.psu.edu/spring-plants-that-are-poisonous-to-horses-dogs-and-barn-cats
[2] - https://www.petmd.com/horse/poisoning/plants-toxic-to-horses-what-to-know
[3] - https://extension.psu.edu/plants-toxic-to-horses
[4] - https://extension.umn.edu/horse-pastures-and-facilities/plants-deadly-horses
[5] - https://equusmagazine.com/horse-care/10-most-poisonous-plants-for-horses-8208
[6] - https://www.dvm360.com/view/plants-poisonous-horses-neurotoxic-variety
[7] - https://www.sweetriverequineclinic.com/blog/twelve-plants-poisonous-to-horses.html
[8] - https://horsesidevetguide.com/drv/Diagnosis/1212/poisoning-by-cardiotoxic-plants-generally/
[9] - https://jessicaeblack.org/how-to-identify-plants-in-your-pasture/
[10] - https://edis.ifas.ufl.edu/publication/VM247
[11] - https://equine.ca.uky.edu/content/which-grasses-should-you-plant-your-pastures-seed-selection-pasture-renovation
[12] - https://www.eesi.org/articles/view/the-climate-and-economic-benefits-of-rotational-livestock-grazing
[13] - https://grassworks.org/wp-content/uploads/2016/11/A-Guide-to-Rotational-Grazing.pdf
[14] - https://www.rspca.org.uk/adviceandwelfare/pets/horses/health/poisoning
[15] - https://www.nwcb.wa.gov/pdfs/Final-WSNWCB-toxic-booklet_low_res.pdf
[16] - http://www.whmentors.org/saf/poison.html
[17] - https://www.aspca.org/pet-care/animal-poison-control
[18] - http://www.ontario.ca/page/common-plant-poisonings-horses-and-their-investigation