top of page

What does being "Grass Affected" mean for Horses?

How to help a grass affected horse, pony or donkey
We have been a horse rescue centre and sanctuary for nearly twenty years.

It has been through working with so many unwanted horses over this time that we realised that many of them were being deemed dangerous and given up on simply because they were being detrimentally affected by grass.

Thankfully, we also experienced that in 99.9% of cases, once the right recovery plan was implemented, these horses could return to their usual selves, with improved health, temperament and behaviour, to being 
calm and trusted equine companions again.  

This unique situation has allowed us to be in the privileged position to take a really deep look and study this condition hands-on, with not only a few grass-affected horses but thousands of them, both through our centre and when helping owners with the recovery of their horses in the community too.

Please read on to learn more:

So, why does grass change a horse from being calm and reasonable

into being unpredictable and dangerous?


You can see the blue spikey molecule in the photo, which is a close-up of a mycotoxin, sometimes called endophytes, found in plants. In our experience, we have found without a shadow of a doubt that the single biggest threat to our New Zealand Horses is from these Mycotoxins found in pasture, chaffs and hays........ and this is why:


Contrary to popular belief, plants do not want to be eaten by horses or any other animals for that matter. Therefore, over millions of years of their evolution, they have developed a sophisticated method of trying to stop that from happening by using chemical warfare on any animals that try to eat or damage them.


Stinging Nettles are a classic example of this, as they release chemicals when under threat that sting, which leaves a clear signal in the memory of any offending animal, which says do not trample or eat me or there will be consequences. And Mycotoxins work in a very similar way, but instead of leaving a nasty sting, they make the animal feel ill as they are slowly poisoned by a built-in type of mould, which is called Mycotoxicosis.


This attacks the animal's central nervous system, causing a host of unwanted symptoms to both the body and mind that can kill the horse if not addressed either by organ failure or through a fall or accident, often brought on by the hysteria which can be an accompanying symptom of this condition. 

Quick and easy solutions for grass affected horses
mycotoxins and horses, toxin binders and recovery
How to get your calm, healthy horse back after grass
agressive behaviour horse
Why does grass cause issues for horses

This rarely happens with wild horses, as the horse's family group teaches the foal what is safe to eat and what is not. In turn, the herd members learn to avoid plants and grasses that contain mycotoxins and/or their stronger cousins in aflatoxins, which are also present in some plants and grasses.


However, our domestic horses normally have to cope with the grasses and plants contained within their paddocks, which are unfortunately often made up of vegetation with high levels of mycotoxins. These Mycotoxins occur in pastures both naturally and through cross-bred grasses that have been man-made to have amplified levels of mycotoxins to help deter insect and rodent damage for farming purposes. These grasses have been bred to have much stronger levels of plant toxins in them that are unnaturally hardy and therefore survive drought and frosts etc....but also, because they have been bred to be so hardy, unfortunately, they tend to take over and invade our pastures and cause severe illness, injury, anxiety and distress to our equine friends, which can lead to aggression through fear as is often exhibited when suffering with Mycotoxicosis. Mycotoxins can also trigger other illnesses, such as laminitis and colic, amongst many other conditions causing inflammation and stressors on the body. 


The other risks from mycotoxin exposure stem from our horse's behaviour becoming hypervigilant and deteriorating into a heightened and elevated state of distress, as we often see is what happens when these poisons have been consumed by the horse for several weeks without treatment, which creates safety issues for their caretakers and riders as they can become unpredictable and behave out of their typical character, that if not corrected can cause severe risks through them doing something extreme like jumping out of the paddock or falling and injuring themselves or those around them. 

Therefore, this must be addressed quickly and treated ASAP.


The photo shows Dash's soft and trusting eye, who arrived to us in a heightened and aggressive state after being given up on by his owner.  He was scared and did not understand the effects of the toxins on his body and vision, which led to him rearing from the anxiety and distress that he was experiencing from the effects of the mycotoxicosis. Dash fully recovered from these dangerous effects in just a few days of using our Equi-Protect detox formula along with some easy grass management-to view our recovery plan please see this link:


Mineral and vitamin imbalances are rife in our New Zealand pastures for many reasons, including soils that are bleached by the harsh UV rays of the sun due to the depletion of the protective layer of ozone over New Zealand.

These deficiencies can cause excitability and overreactive behaviours in our horses, plus a long list of various health conditions, which can be easily corrected by adding a daily dose of a correctly balanced  Equine Vitamin and Mineral supplement to replace the components missing or low from the horse's diet.

We highly recommend our Natural Horse Equine Vit and Mineral formula, which has been specifically developed to address the issues of Grass Affectedness, and provides a specially blended mix of vitamins, minerals, and amino acids to address shortfalls and fill these nutritional gaps for improved health and temperament.

best ways to sort ou grass issues in horses
what causes grass problems in horses
Due to environmental factors and our temperate conditions, New Zealand pastures often contain excessively high levels of plant sugars in the sap of the plants and grasses that are called fructans that our horses eat.

Horses have evolved to eat a staple diet of low-sugar brown tussock grasses and other brown top plants, so when we expose them to a 24/7 diet of lush green pasture this can have an adverse effect on their health, that is very similar to diabetes in humans, which can lead to various health issues along with unwanted excitability due to the excess energy provided by eating copious amounts of these fructan-rich grasses.

Feeding more low-sugar grasses in the form of plainer meadow hays fed by a Slow Feeder Haynet, and less green grass is the best way to help your horse replicate a diet more suited to his natural dietary needs, which can also be beneficial in preventing other conditions such as laminitis and ulcers too, please see our track grazing pages and other articles to learn more on how to manage this.