Things That Are Toxic To Donkeys

Close up of a donkey's eye.

April 7, 2022 review and update in progress.

It can be a challenge to ensure donkey residents have healthy, happy lives after coming to a sanctuary, and there are many different aspects of care to consider each day. Unfortunately, toxic and poisonous hazards are sometimes overlooked in the hustle and bustle of operating a sanctuary. While minor exposure to many of these toxins is unlikely to cause serious problems, large amounts can cause severe health issues and sadly, even death. There are also some toxins that are highly dangerous even in small amounts. Remember, donkeys are different from horses and less likely to show symptoms of illness so it is imperative any slight change in behavior is noted and addressed.

In order to help ensure you never run into this problem, we have compiled this resource of common plants and other potentially toxic things that have been known to be a problem for donkeys.

Plants That Are Toxic To Donkeys

Please see The Open Sanctuary Project’s Global Toxic Plant Database and filter Species Afflicted by equines in order to see a list of plants across the world that are toxic to donkeys. Please note that, while comprehensive, this list may not contain every single plant toxic to donkeys!

Plants Toxic To Horses | PennState Extension (Non-Compassionate Source)

Other Potential Donkey Toxins

Blue-Green Algae

Blue-green algae are usually often found in stagnant, slow-moving water when temperatures are high. Consumption of this algae can result in the poisoning of donkeys and other animals. Symptoms often occur quickly after ingestion. Symptoms may include lethargy, lack of appetite, colic, hypersalivation, seizures, coughing, frothing at the mouth, labored breathing, and diarrhea. Liver failure is possible if certain types are ingested in large enough amounts. In severe cases, donkeys may collapse and die. Photosensitization may be a delayed result of ingestion, causing reddening and irritation of the area around the mouth, the ear, or other areas of the body.


Avoid Risks to Horses from Blue-Green Algae | Kentucky Equine Research (Non-Compassionate Source)

Blue-Green Algae Poisoning in Horses | College Of Agriculture, Food, And Environment: Equine Programs (Non-Compassionate Source)

Cantharidiasis (Blister Beetle Poisoning)

Blister beetles contain cantharidin, a toxic substance that is used as a defense mechanism against predators. There are many different species, found from Mexico to Southern Canada, and from the east coast of the United States as far west as New Mexico. Cantharidin can severely injure or kill donkeys when even a small amount of the poison is ingested. Horses come into contact with cantharidin by ingesting alfalfa hay that has been infested by blister beetles. The cantharidin, an oily substance, can contaminate hay when beetles are crushed in the harvesting process. 

Inspecting individual flakes of alfalfa hay before providing them to residents can help reduce the likelihood of poisoning. If you find a flake with evidence of a blister beetles presence, dispose of the flake, even if you have removed the beetle. First-cutting hay is generally less likely to be contaminated than hay harvested later in the year, as the beetles are more likely to swarm later in the season. You can possibly reduce the chances of contamination if you harvest alfalfa before it fully blooms. Harvesting with a self-propelled mower or windrower may help reduce contamination as well. Crimping hay crushes the beetles in the bales.

Horses that ingest enough toxin may show signs of severe shock, and unfortunately, die within hours. Classic clinical signs are dark, congested mucous membranes, and frequently drinking small amounts of water or submerging the whole muzzle in water. Other signs include colic, depression, anorexia, ulceration of oral mucous membranes, a purple-blue line on the gums, diarrhea, polyuria (excessive urination) leading to dysuria (difficulty urinating), dehydration, sweating, delayed capillary refill time, tachycardia (abnormally rapid heart rate), tachypnea (abnormally rapid breathing),  contractions of the abdominal muscles, collapse, and death.

If you suspect Blister Beetle Poisoning, contact your veterinarian immediately. Recovery may be possible if it is caught and treated early.


Blister Beetle Poisoning | American Association Of Equine Practitioners

Cantharidin Toxicosis From Blister Beetles In Horses | Today’s Veterinary Nurse

Grain Overload (Carbohydrate Overload)

Grain overload occurs when donkeys eat large amounts of grain, causing high amounts of carbohydrates to be released into the large intestine as the small intestine will be “overloaded” and unable to digest that amount normally. Lactic acid is produced in high amounts, wreaking havoc in the digestive system. Grain overload can cause colic and laminitis and, in serious cases, can be fatal.  While not all cases develop into serious illness, depending on the amount consumed and the individual’s health, it should always be taken seriously. If you know a resident has overconsumed, don’t wait for problems to arise, call your vet.

Grain overload is most commonly seen when donkeys gain access to bins or bags of grain or have an outdoor living space that has had grains recently harvested, leaving excessive leftover grain. Grain overload can also happen if a donkey resident has a change in diet too quickly as opposed to a gradual shift to concentrates or grains.

Signs of grain overload include:

  • Bloating
  • Abdominal pain
  • Recumbancy
  • Pawing the ground
  • Kicking or biting at flank
  • Reluctance to move
  • Lack of appetite
  • Trembling
  • Sweating
  • Depression, dullness
  • Lethargy
  • Diarrhea
  • Increased heart rate
  • Increased respiratory rate
  • Laminitis
  • Heat emanating from hoof wall or foot
  • Digital pulse present in the foot
  • Death in serious cases

If you suspect a donkey resident has grain overload, contact a veterinarian immediately. The sooner treatment can begin, the better.  The course of treatment will depend on the severity of the condition.


Laminitis| Stillwater Equine Veterinary Clinic

Grain Overload, Horse Got into Feed Room | Horse Side Vet Guide

Hardware Disease

Hardware Disease refers to the injuries that can result from any animal resident eating something they shouldn’t, especially pieces of human-made hardware like nails, screws, and staples. Hardware disease can have devastating effects on any resident. Check out our resource on Hardware Disease prevention here.

Lead Toxicity

Lead was once used in paints and pesticides, and can also be found in natural environmental sources. Even if you have never used any products containing lead, it may still be present in old barn or fence paint, or in the soil. Places, where old machinery and leaded gas have been stored, may also have caused contamination, as would old treated lumber and railroad ties. Horses may ingest the lead in the environment through the consumption of grass, clover, and dandelion or from chewing or licking on tainted surfaces.

Having the soil tested at your sanctuary is an easy way to learn if the environment is safe for residents. You can check with a local environmental conservation service, or agricultural extension office to inquire about testing. It is usually a fairly quick and easy process. Prevent your residents from accessing buildings and fences with old paint, as they may chew or lick these objects and ingest lead.

Chronic poisoning is usually more common than acute poisoning though both are possible. Horses with low levels of lead toxicity do not generally exhibit signs. In more serious cases, you may see the following symptoms:

  • Loss of appetite
  • Weight loss
  • Depression
  • Lethargy and weakness
  • Incoordination
  • Colic
  • Paralysis of the pharynx
  • Difficulty Swallowing
  • Unusual manure consistency or diarrhea
  • Respiratory distress 

Consult a veterinarian immediately if you suspect your donkey has ingested lead or is beginning to show symptoms of lead poisoning.


Lead Poisoning in Animals | The Merck Veterinary Manual

Lead Poisoning | Clinical Veterinary Advisor 

Is There Lead In Your Pasture? | Of Horse (Non-Compassionate Source)


Mycotoxins are toxins produced by fungi that can be harmful to donkeys and many other animals. Different species are more susceptible to different types of mycotoxins.  Mycotoxins can affect donkeys through contaminated food (hay or concentrates or grains) or bedding. Moist, warm environments make a perfect recipe for fungal reproduction. Horses may be affected through inhalation or ingestion. Symptoms and severity of mycotoxin poisoning in donkey residents can vary greatly, depending on the type of mycotoxin. Some signs of mycotoxin toxicity include:

  • Liver damage
    • Jaundice
    • Swelling of the head and neck
    • Seizures
    • Depression
    • Loss of appetite
    • Paralysis of the tongue
    • Coma
  • Neurological disease (leukoencephalomalacia)
    • Drowsiness
    • Circling
    • Pharynx paralysis
    • Blindness
    • Apathy
    • Incoordination
    • Staggering
    • Hyperexcitability
    • Recumbency
    • Death
    • Neurological deficits in survivors
  • Reduced weight gain
  • Appetite loss
  • Weight loss
  • Respiratory issues
  • Difficult labor, lack of milk production, and/or  fetal loss in pregnant mares
  • Death

Prevention is key in avoiding serious health issues. Luckily, there are a number of steps you can take to help ensure resident donkeys do not suffer the ill effects of mycotoxin poisoning:

  • Be sure to keep grain, concentrates, and hay storage areas clean, dry, and cool
  • Try to keep food storage areas protected from mice and rats and other wildlife, as they can chew holes in food bags, increasing the likelihood of grain being exposed to damp conditions
  • Always feed the oldest bags of food first. Try to use up open bags within a few weeks after opening in the winter and in even less time in the summer
  • Clean any storage bins or cans thoroughly to remove old grain that gets stuck in cracks and crevices
  • Check with your food manufacturer or supplier to see if they regularly test for the presence of mycotoxins in grains before mixing food. If they do not, avoid using them and find another supplier
  • Avoid corn screenings (small parts of corn grain  completely

If you are concerned about the possibility of mycotoxin contamination, have your food stores tested. This could be especially important if you have a donkey that shows initial signs of mycotoxin exposure.


The Danger Of Mycotoxins | The Horse (Non-Compassionate Source)

Molds, Mycotoxins and their Effect on Horses | Ministry Of Agriculture, Food, And Rural Affairs (Non-Compassionate Source)

Equine Leukoencephalomalacia | Purdue University  (Non-Compassionate Source)

Opossum Feces

Opossums are wonderful animals that do a lot for our local ecosystems. However, if you care for equine residents and live in an area where possums also live, you will need to be vigilant and ensure residents do not come in contact with opossum feces. Opossum feces can carry the protozoan that is responsible for causing equine protozoal myeloencephalitis (EPM). This is a serious neurological disease that affects donkeys and donkeys can become infected by ingesting food or water contaminated with opossum feces. This usually happens when an opossum may get into a food storage area and leave waste behind on hay that donkeys will eventually eat. Be sure you check hay for waste and dispose of any contaminated hay.

You can read more about compassionate ways to manage wildlife populations at your sanctuary here!

Signs of equine protozoal myeloencephalitis:

  • Stiffness
  • Abnormal gait
  • Lameness
  • Incoordination
  • Difficulty swallowing
  • Drooping eyes, ears, and/or lips
  • Head tilting
  • Standing play-legged
  • Seizures
  • Collapse
  • Muscle atrophy
  • Facial nerve paralysis

If you find hay that has opossum feces and you think a resident could have consumed any, speak with your veterinarian immediately. Early treatment has higher rates of recovery among infected individuals.


Equine Protozoal Myeloencephalitis (EPM) | University Of Minnesota Extention (Non-Compassionate Source)

Equine Protozoal Myeloencephalitis (EPM) | UC Davis Veterinary Medicine (Non-Compassionate Source)

Other Animal Food

While you may think it is okay to substitute donkey food for cow, goat, or bird food in a pinch, it can actually cause serious health issues for donkey residents. Non-medicated cow, goat, and bird foods are not good for your donkey residents and can cause colic or other health issues, and medicated feeds can be fatal!

Medicated food for many other animals at sanctuaries contains rumensin or monensin and other ionophores (antibiotics) to control disease. However, ionophores are EXTREMELY toxic to donkeys. The safest bet is to only give species-appropriate food to donkeys, and design food storage rooms to prevent cross-contamination. Be sure food areas are secure from curious residents that may try to sneak in for a midday snack!

Horses that have ingested food with ionophores may exhibit:

  • restlessness,
  • sweating,
  • Weakness
  • Incoordination
  • Abnormally high heart rate
  • Frequent urination
  • Colic
  • Recumbency
  • Inability to rise
  • Thrashing
  • Heart damage
  • Death

Sadly, severely affected donkeys may die within 12 to 36 hours after exhibiting symptoms. 


Don’t Give Cattle Feed To Horses! | Kentucky Equine Research (Non-Compassionate Source)

Help! My Horse Ate Chicken Feed: What Should I Do? | The Horse (Non-Compassionate Source)

My Horse Just Ate Chicken Feed. Is He Going To Be Okay? | Exclusively Equine Veterinary Service (Non-Compassionate Source)

Review Of Monensin Toxicosis In Horses | Journal Of Equine Veterinary Science (Non-Compassionate Source)

Pesticides, Herbicides, And Rodenticides

It may not come as a surprise that herbicides, pesticides, and rodenticides can cause toxicosis in donkeys if ingested. If donkeys ingest plants that have been sprayed with certain types of herbicides, they can become ill or even die. Certain herbicides can actually increase the toxicity potential of certain plants. For this reason, it is imperative that donkeys are not given treated plants or are allowed access to pastures that have been treated with toxic herbicides. While poisonings are not often seen, herbicides that contain chlorates or arsenic, as well as some others, can be toxic and cause health issues. Be sure to research any herbicides to determine safety risks before using where residents might come in contact. When poisonings occur, it is often due to improper dilution rates, improper storage, or the combination of certain herbicides on plant matter.

Signs of herbicide poisoning:

  • Diarrhea
  • Weakness
  • Colic
  • High heart rate
  • Blood or mucous in stools
  • Salivation
  • Collapse
  • Respiratory distress
  • Drooling,
  • Anorexia
  • Little to no urine
  • Death

While rats and mice can pose challenges for sanctuaries, it is important to respect them and use compassionate mitigation practices. Many rodenticides are anticoagulants and act by preventing the blood from clotting. These products may be appealing to donkeys as well, and they may attempt to lick or eat them if discovered. For this reason, it is imperative that they do not come into contact with these poisons. There are many new and innovative ways to address rodent populations that are more effective and compassionate.

Signs of rodenticide poisoning:

  • Depression
  • Pale mucous membranes
  • Stiffness
  • Nervousness
  • Weakness
  • Blood in feces or urine
  • Lameness
  • Bleeding from gums or nose
  • Respiratory distress
  • Distended abdomen
  • Muscle tremors
  • Abnormal heart rate
  • Thrashing
  • Death

Pesticides may affect the nervous system in donkeys and can be fatal if not treated. Early treatment is critical. Signs of pesticide poisoning include:

  • Increased tear production
  • Excess salivation
  • Excessive urination
  • Excessive defecation
  • Diarrhea
  • Colic
  • Respiratory distress
  • Low heart rate
  • Contracted pupils
  • Muscle tremors or twitches
  • Weakness
  • Paralysis
  • Death

If you suspect a donkey may have ingested any of the poisons above, contact your veterinarian immediately. Blood tests may confirm poisoning.


Toxin Topic: Anticoagulant Rodenticides | University Of Kentucky, Equine Programs

Toxicosis From Agricultural Chemicals | Science Direct


While sanctuaries in some areas do not have to worry about venomous snakebites, other areas have a number of venomous species. Snakebites are generally uncommon, but when they occur, should be treated seriously and immediately. The most common location for a donkey to be bitten is on the nose or leg.  A snake can bite multiple times, so if you notice a snakebite, look for others. Snake venom varies by species, and the severity of a bite can also be influenced by their size and age, and the number of bites. Most venoms can impair blood clotting and damage the heart, while some others contain neurotoxins. Signs of snakebite may include:

  • Pain
  • Swelling at the bite site
  • One or more puncture wounds
  • Sloughing of tissues near the bite site
  • Cardiac arrhythmias
  • Impaired ability for their blood to clot
  • Labored breathing
  • Shock
  • Collapse
  • Paralysis
  • Death

Seek veterinary care immediately if a donkey is bitten by a venomous snake. Do NOT try to suck the venom out or place a tourniquet. Keep the donkey calm while seeking immediate veterinary care. Depending on the severity of the bit, treatments may include antivenin, pain medications, fluid therapy, wound treatment, tetanus vaccination, and antibiotics. Check out our Compassionate Wildlife Practices At Your Animal Sanctuary for some tips on how to dissuade snakes from your property.

Toxin Topic: Snakebites And Horses | University Of Kentucky, Equine Programs (Non-Compassionate Source)

Do You Know The Signs And Symptoms Of Equine Snake Bite? | Scone Equine Hospital

Wood Stains And Paints

Some wood stains and paints can be toxic to donkeys. Horses may try to chew on painted surfaces and can become ill if the stain or paint is toxic. Try and purchase paints and stains that are specially made for barns and fencing and listed as animal or “livestock” friendly.


Animal-Friendly Barn And Fence Paint For Horse Stalls | Stuff For Petz

While this list isn’t exhaustive, it can certainly help you keep resident donkeys safe, healthy, and happy! 

If a source includes the (Non-Compassionate Source) tag, it means that we do not endorse that particular source’s views about animals, even if some of their insights are valuable from a care perspective. See a more detailed explanation here.

Updated on April 7, 2022

Related Articles

Support Our Work
Please consider supporting The Open Sanctuary Project by making a donation today! We are 100% donor-funded and rely on the support of generous individuals to provide compassionate resources to animal caretakers worldwide.
Donate Now HERE