Introduction
Proper nutrition is vital for maintaining the health and performance of adult horses. While horses are herbivores with a digestive system adapted for grazing, many common foods and plants can be toxic or cause serious harm. This guide provides a comprehensive list of dietary restrictions for adult horses, covering dangerous plants, grains, supplements, and other substances.
Plants Toxic to Horses
Many ornamental plants and weeds are poisonous to horses. Ingesting even small amounts can lead to colic, neurological issues, or death.
- Red Maple (Acer rubrum): Wilted or dried leaves cause hemolytic anemia, weakness, and dark urine. Avoid any exposure.
- Yew (Taxus spp.): All parts are highly toxic, causing sudden death due to cardiac arrest. Even a few leaves can be lethal.
- Ragwort (Senecio jacobaea): Contains pyrrolizidine alkaloids that damage the liver, leading to chronic wasting and photosensitivity.
- Bracken Fern (Pteridium aquilinum): Causes thiamine deficiency and neurological signs like ataxia and blindness.
- Oleander (Nerium oleander): Extremely toxic, causing colic, tremors, and death even in small amounts.
- Black Walnut (Juglans nigra): Shavings used as bedding can cause laminitis, but ingestion of nuts or leaves may also be harmful.
- Nightshade (Solanum spp.): Contains solanine, causing GI upset and neurological symptoms.
- Poison Hemlock (Conium maculatum): Causes paralysis and respiratory failure.
Grains and Feeds to Avoid
While grains are common in horse diets, certain types or preparations can be dangerous.
- Moldy Corn: May contain mycotoxins like fumonisin, which causes equine leukoencephalomalacia (blindness, incoordination, and brain damage).
- Spoiled Hay or Silage: Can harbor mold or bacteria causing colic, diarrhea, or botulism.
- High-Starch Concentrates: Excessive grain (especially corn, barley, oats) may lead to colic, laminitis, and insulin resistance. Meals >2.5 kg per feeding should be avoided.
- Unsoaked Beet Pulp: Can expand in the stomach, causing impaction. Always soak before feeding.
Harmful Supplements and Additives
Some supplements or additives can be toxic when overfed.
- Monensin and Ionophores: Used in cattle feed, extremely toxic to horses, causing severe heart damage and death. Never feed cattle supplements to horses.
- High Vitamin D: Excessive supplementation causes calcification of soft tissues, kidney damage, and lameness.
- Iron Overload: Horses rarely require iron supplementation; excess can cause liver damage and laminitis.
- Garlic and Onion Powder: In large amounts, they can cause Heinz body anemia.
Human Foods and Treats
Many human foods are unsafe for horses.
- Chocolate: Contains theobromine, which is toxic to horses, causing seizures and heart issues.
- Avocado: Contains persin, which can cause colic, respiratory distress, and even death.
- Fruit Pits and Seeds: Apple seeds, cherry pits, and peach pits contain cyanogenic glycosides, which release cyanide. Remove pits before feeding fruit.
- Coffee and Tea: Caffeine can cause hyperactivity and heart problems.
- Sugar-Free Products with Xylitol: Causes rapid insulin release and hypoglycemia.
- Rhubarb Leaves: Contain oxalates that cause kidney damage and colic.
Other Dangerous Substances
- Lawn Clippings: Ferment quickly and can lead to colic or laminitis; avoid feeding fresh clippings.
- Blister Beetles: Found in alfalfa hay, contain cantharidin, which causes severe GI inflammation and colic. Source hay from regions with low beetle presence.
- Salt: While needed, excessive salt can cause dehydration and electrolyte imbalances. Ensure fresh water is always available.
Signs of Toxicity and Emergency Action
If a horse ingests any of these substances, look for signs like colic, depression, tremors, dark urine, or difficulty breathing. Contact a veterinarian immediately. Remove the horse from the source and provide fresh water. Do not induce vomiting unless directed.
Safe Feeding Practices
To prevent accidental poisoning, inspect hay and pasture regularly for toxic plants. Feed only commercially prepared feeds designed for horses. Introduce new foods gradually. Store all supplements and grains in labeled, sealed containers away from horses. Provide a balanced diet with appropriate forage, clean water, and a low-starch concentrate if needed.
Conclusion
Knowing which foods and plants are toxic to adult horses is essential for responsible care. By avoiding these common hazards, owners can protect their horses from serious health problems. Always consult with a veterinarian or equine nutritionist when in doubt about specific feeds or pasture plants.