Nightshade Poisoning in Horses: Symptoms and Treatment
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Along with all the other tasks that come with caring for a horse, taking time to regularly check pastures and hay for weeds or other unwanted surprises is an important habit for any attentive horse owner.
One of the most important weeds to watch for is nightshade. Plants in the Solanaceae family like nightshade are extremely toxic to horses, and even though most horses don’t find them very tasty, their powerful toxins still make them a serious concern.
Key Takeaways
- The berries and leaves of a nightshade plant are the most toxic portions; even ingesting very small quantities can cause illness in horses.
- Nightshade plants contain substances called steroidal alkaloids that block neurotransmitters from firing.
- Common symptoms of nightshade poisoning include colic and neurological changes like depression and muscle weakness.
- If you suspect nightshade poisoning in your horse, contact your veterinarian right away and if possible, keep the plant on hand to help with identification.
What Is Nightshade Poisoning in Horses?
Nightshade poisoning occurs when a horse eats portions of a nightshade plant. The leaves and berries are the most harmful parts of the plant, as they contain the highest concentrations of toxic substances called steroidal alkaloids.
These toxins harm horses by interfering with neurotransmitters in the nervous system, preventing nerves from sending signals the way they should. When those signals are disrupted, multiple organ systems can be affected—including the digestive tract, heart, lungs, and nervous system—leading to serious health problems.
Symptoms of Nightshade Poisoning in Horses
When a horse is exposed to a nightshade plant, its toxins can disrupt normal neurotransmitter activity, affecting several organ systems and causing the following symptoms:
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Colic (abdominal pain): rolling, pawing, biting at the sides
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Little or no appetite
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Depression/dullness
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Dilated pupils
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Muscle weakness
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Ataxia (lack of coordination)
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Paralysis
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Changes in heart rate
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Difficulty breathing
Causes of Nightshade Poisoning in Horses
Nightshade plants are an undesirable food source for horses, and most will avoid them if given other options. However, when pastures are overgrazed and forage is limited, horses may turn to eating nightshade simply because they have no better options.
Most poisonings occur when a nightshade is accidentally baled into hay or processed into feed. For this reason, horse owners and barn managers should always inspect each horse’s food before feeding.
How Veterinarians Diagnose Nightshade Poisoning in Horses
If you suspect nightshade poisoning in your horse—whether because of symptoms or because you’ve found the plant in a bale of hay or nibbled on in the pasture—call your veterinarian right away.
Your vet will perform a full workup, including a physical exam and bloodwork, to determine the severity of poisoning. Some of these tests can be done “stall side,” but others may take days to weeks to get results. In the meantime, your veterinarian will start supportive care based on the presumptive diagnosis.
Treatment of Nightshade Poisoning in Horses
If nightshade poisoning is diagnosed, treatment mainly consists of supportive care, including pain medications like Banamine and IV fluids with or without electrolytes.
Severe cases may require hospitalization and medications, such as neostigmine, to help reverse or at least decrease the effects of the toxin on the neurotransmitters.
Recovery and Management of Equine Nightshade Poisoning
Recovery from nightshade poisoning depends largely on how severely the horse is affected.
In mild cases, horses may recover with prompt care, but in more serious situations, the damage can be life-threatening. Mild cases often just take time, supportive care, and pain management for a horse to recover. There may be some residual side effects seen, such as weakness, but in most of these cases there are no long-term consequences.
Some horses may die from complications, such as difficulty breathing or coma, while others may need to be humanely euthanized due to severe symptoms like intense colic or paralysis.
It’s very important to remove all possible sources of nightshade to prevent continued exposure to your horse. This means checking all hay and feed before giving it out, and walking fields and pastures to check for nightshade weeds.
Prevention of Nightshade Poisoning in Horses
Horse owners can take several steps to help prevent nightshade poisoning, including:
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Checking fields and pastures regularly for weeds and removing any possibly poisonous ones
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Ensuring horses who are grazing have sufficient access to food, especially when the grass is gone for the winter, by supplementing hay if needed
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Checking all hay bales and other feed products for contaminants daily
Nightshade Poisoning in Horses FAQs
What are the symptoms of plant poisoning in horses?
The first symptoms seen with nightshade poisoning often mimic signs of colic, such as rolling, pawing, and biting at the sides. In more severe cases or as the condition progresses, additional symptoms may include depression, dilated pupils, muscle tremors, weakness, and collapse. If you have concerns about nightshade poisoning, contact your veterinarian right away.
How toxic is nightshade to livestock?
Horses seem to be the most sensitive to nightshade’s toxic effects, although the plants are toxic to cattle, sheep, and goats as well.
What does poisonous nightshade look like in a horse’s pasture?
There are several species of plants within the nightshade family, but most are green with small flowers and green berries that turn purple or black when ripe.
