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How to Prevent and Treat Plant Poisoning in Horses

Poisonous plants that are toxic to horses and other livestock exist everywhere in the world. They are so common, a toxicologist at Utah State University, Jeffery Hall (DVM, Ph.D.), says, “I defy anyone to tell me they have a pasture with zero poisonous plants.” 

Although horses are pretty selective about what they eat and find most toxic plants unpalatable, with the most poisonous plants, even a tentative bite could deliver a lethal dose.

I’ve lost several horses to plant poisoning but, over time, I’ve also figured out a way to minimize the effects and reduce the risk of them consuming a lethal dose.

Many of the signs of poisoning reveal themselves only once the horse has reached a critical stage, making prevention a much better option. 

How to Make Sure Your Horse Isn’t Eating Toxic Plants

Knowing your enemy is key to preventing plant poisoning.

If you can identify the most common toxic plants in your area, you can potentially eradicate them.

Even if you can’t remove it altogether, you can familiarize yourself with a poisonous plant so that you know when it poses the biggest threat.

Check out the video below to learn more about common pasture weeds and how to identify them.

On our small-holding, for example, we have two types of toxic plant – a member of the Senecio family and Lantana.

The Senecio shoots at the beginning of summer when the rains begin, so this is the time my horses are confined to a small paddock and fed a princely diet of concentrates and alfalfa.

Once the Senecio reaches five inches in height, the bitter taste becomes more apparent. Its flavor and height make it easier for the horses to identify and, subsequently, avoid the weed.

4 Natural Products to Prevent Damage From Toxic Plants

The widespread nature of the Senecio species means I can never be 100% sure that my horses aren’t eating something toxic.

To be on the safe side, I keep them on a regime of natural supplements to limit the damage and keep the signs of poisoning to a minimum. 

A horse with Senecio poisoning displays all the most common signs of poisoning, including loss of appetite, weight loss, muscle tremors, and lack of coordination.

These symptoms are often only visible once the situation is critical and it’s too late to reverse the process or save the horse. 

My preventive regime, therefore, focuses primarily on maintaining the digestive system, keeping liver function optimal, and boosting bile production. 

1. Activated Charcoal 

Charcoal Powder (Activated)
Charcoal Powder (Activated)
from Starwest Botanicals Inc. 

To help the horses get rid of any toxins they may have ingested, we put them on a course of activated charcoal for 10 days at a time.

During this period, they get a dose of approximately 0.04 – 0.14 oz  (1-4 grams) per 2.2 lb (1 kg) of body weight.

In cases of severe poisoning, vets will administer activated charcoal via a nasogastric tube but, for purposes of prevention, we simply add it to their daily concentrate.

To prevent and treat liver damage, we keep our horses on a regular diet of milk thistle, garlic, and turmeric.

2. Milk Thistle

Milk Thistle Seeds - Starwest Botanicals
Milk Thistle Seeds – Starwest Botanicals
from Starwest Botanicals Inc. 

The benefits of milk thistle haven’t been widely researched and the studies that have been conducted have produced inconclusive results.

Nevertheless, milk thistle contains silymarin which has antioxidant and anti-inflammatory properties. As a result, it “can protect liver tissue from damage and support the function of the liver.”

The easiest way to feed milk thistle is by adding a few grams of milk thistle seed powder to your horses’ concentrate every day.

Start with just 2 grams a day and then gradually increase it until you reach the “recommended dose of 4.5 grams per day for an 1100 lb (500kg) horse.”

3. Garlic

Garlic - Starwest Botanicals
Garlic – Starwest Botanicals
from Starwest Botanicals Inc. 

While your horse may not be overly impressed the first time you add garlic to his daily feed, he will get used to the strong flavor in due course and get all the benefits of this powerful medicinal plant.

Garlic contains selenium which helps to trigger your horse’s liver enzymes, naturally flushing out any toxins he may have consumed. 

The easiest way to introduce garlic to your horse’s diet is by using it in either granule or powdered form, but experts recommend fresh, organic garlic as being both the most effective and the safest.

A daily dose of around 1 oz (30 grams) a day is recommended for an average horse of around 990 lb (450 kg) but can be increased to 1.8 oz (50 g) for larger animals.

4. Turmeric

Turmeric | Curcuma longa | Dried Spices | Culinary Spices
Turmeric | Curcuma longa | Dried Spices | Culinary Spices
from Starwest Botanicals Inc. 

Containing the powerful anti-inflammatory, curcumin, turmeric has many benefits for your horse’s health.

Curcumin stimulates the gallbladder’s production of bile which the liver uses to eliminate toxins and rejuvenate the cells responsible for breaking down harmful compounds, such as those found in toxic plants.

The problem with curcumin is that it’s not easily absorbed into the bloodstream.

One of the best ways of improving the absorption rate, and enhancing the benefits of the curcumin itself, is by mixing it with black pepper.

The piperine in black pepper increases curcumin absorption by up to 2,000% while “slowing degradation and allowing more time for the curcumin to be absorbed.”

Fats also help the absorption of curcumin so most experts recommend mixing the turmeric and black pepper with a fatty oil, like linseed or flax oil, to boost the absorption rates even further. 

If you’ve got an average-sized horse of around 1100 lb, a daily dose of around 25mg turmeric powder should be effective.

Combine the turmeric with a few grinds of black pepper and two tablespoons of oil to create a paste that you can add to your horse’s feed.

Grazing Management Is the Best Way to Prevent Poisoning

Keeping your horses away from poisonous plants through proper grazing management is the best way to prevent the symptoms of poisoning.

You can, for example, prevent liver damage from an annual plant by restricting your horses’ grazing for a specific period.

However, that’s not always enough, especially if you’re dealing with plants from the Senecio family which produce pyrrolizidine alkaloids that accumulate in the horse’s system.

As many of the signs of poisoning occur only once the situation has become critical, prevention is the most effective course of action.

Using natural substances, like activated charcoal, milk thistle, turmeric, and garlic, can help to support the horse’s immune and digestive systems. This gives your horse a better chance of flushing out any toxic elements and thereby reducing the risk of liver failure.

I feel the need to add that I’m not a veterinarian and can only speak from my own experiences in South Africa.

Different types of plant toxicity will require different approaches, both in terms of diagnosis and preventative support.

If you suspect your horse is suffering from plant toxicity, you should contact a veterinarian and get expert advice on how to proceed. 


  • A horse-mad redhead with a passion for the outdoors, Nicky lives on a 6ha small-holding on the Wild Coast of South Africa. She spends her time rearing goats, riding (rearing) horses, and meticulously growing her own chicken food. She has a witch’s knack with herbs and supplements everything, from her beloved Australian Cattle Dog to the occasional passing zebra with the fruits of her labor. Nothing is bought unless Nicky fails to MacGyver it out of scraps of broken bridles, baling twine, or wire. She loves baling twine (and boxes, oddly enough).