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What Should You Do if You Think Your Horse Has a Mycotoxin Problem?

Mycotoxins can contaminate almost everything your horse eats and can cause significant health and behavioural issues. The problem is, figuring out what is causing the problems you are seeing and suspect may be mycotoxins isn’t always easy. This post is going to help you answer the question: what should you do if you think your horse has a mycotoxin problem?

Why mycotoxin binders may (or may not) help

Often when someone suspects mycotoxins they will add a mycotoxin binder to the horse’s feed. Sometimes it will help. But often it may not and this will normally lead a horse owner to the conclusion that the problem isn’t mycotoxins and they continue to struggle along, baffled by what is causing the changes in health or behaviour for their horse.

The problem is, not all mycotoxin binders will bind all mycotoxins. It’s also really very hard to mix mycotoxin binders well enough in a horse’s gut with the forage they eat to actually come into contact and either bind or destroy all mycotoxin. So even if you get the right binder, it may not get the chance to come into contact with the mycotoxins in the horse’s gut to allow it to do its job.

For more information on mycotoxin binders (and what to consider before adding one) click here.

For more detailed info you can read our full article on mycotoxin binders here.

How to know for sure if it’s a mycotoxin problem

Here is what I (Nerida) would do…

Let’s say for example a horse has started to show changes in behaviour: spookiness, aggressiveness or overly herd bound and always wanting their mates. You suspect it is pasture mycotoxins from your ryegrass pasture (sound familiar anyone?!). The best thing to do is to take your horse COMPLETELY off the pasture for a period of time and replace the pasture with hay that is not ryegrass and see if the behaviour settles down.

Doing this completely removes the suspected pasture toxins from the diet and you will see quite quickly if it was the cause of your issues. If the problem settles once the mycotoxin contaminated feed or forage is removed from the diet, you have identified your suspect and now it becomes a matter of managing the problem.

This may involve keeping the horse off pasture completely at high risk times (for example when your ryegrass is overgrazed or gone to seed). You may only allow grazing for short periods of time to limit mycotoxin intake or you may allow your horse to graze but feed an appropriate mycotoxin binder regularly during the grazing period to give it the best chance of coming into contact with the pasture mycotoxins in the gut so it can bind or destroy them.

What not to do…

What I don’t recommend is JUST adding a mycotoxin binder to see if you can make the problem go away. There are many reasons why the issue may be mycotoxins but adding a binder won’t help much. It is much better to take whatever it is you suspect is adding mycotoxin to your horse’s diet away completely. Then there is no grey area of maybe it is/maybe it isn’t… 

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What to Consider Before Adding a Mycotoxin Binder to Your Horse’s Diet

Mycotoxins are nasty little things… toxins produced by fungi that can contaminate feed and forages. They are only needed in tiny amounts (like parts per billion) to have some quite dramatic negative health effects on all animals and different mycotoxins will work together to magnify their negative effects. Read on for more info on what to consider before adding a mycotoxin binder to your horse’s diet.

For horses we mostly deal with pasture based mycotoxins, produced by the endophyte fungi that like to live with ryegrass and fescue; the ergovaline and lolitrem mycotoxins. Horse owners are starting to use toxin binders to counteract the negative effects these mycotoxins have on health and the quite dramatic effects they can have on behaviour.

But, there are lots of different binders and a lot of different toxins…

Do all binders bind all mycotoxins?

In a word… no! And this is where a major key lies to whether mycotoxin binders will work to prevent pasture associated mycotoxin poisoning or not. For example, it has been shown that glucomannan from the yeast Saccharomyces cerevisiae is very effective at binding aflatoxin (one of the most important and prevalent mycotoxins present in grain based livestock feeds) and good ability to bind the fumonisin and zearalenone mycotoxins, but it is ineffective when it comes to binding other important mycotoxins like T-2 (trichothecene), DON (deoxynivalenol) and ochratoxin.

Why don’t all binders work on all mycotoxins?

One of the reasons some binders can bind some mycotoxins and not others depends on the mycotoxin itself and whether it is polar (possessing an electrical charge) or not. Aflatoxin, for example, is a polar mycotoxin and is very easily ‘picked up’ by a yeast derived glucomannan based binder (which are the most common mycotoxin binders on the market for horses). The pasture based mycotoxins ergovaline and lolitrem B on the other hand are non-polar (no charge). That means trying to pick them up with a yeast cell wall based toxin binder is sort of like trying to pick up a piece of paper with a magnet … it just won’t work.

So if you want to use a mycotoxin binder be careful to select one that is going to work on the actual mycotoxin you are dealing with, otherwise it will be an ineffective waste of money for you, and that is never fun!

For more detailed info you can read our full article on mycotoxin binders here.

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Mycotoxin Binders: Do They Work on Pasture Toxins?

There has been a lot of talk in recent years about the effect pasture mycotoxins are having on our horses. While the extreme cases of staggers and pregnancy complications from grasses like perennial ryegrass and tall fescue are well documented it appears that pasture mycotoxins may be having more subtle effects on our horses that until recently have not been well recognised.

In an attempt to reduce the impact of the mycotoxins present in pastures many horse owners have been using mycotoxin binders. But do they work?

THE PROBLEM WITH PASTURES

Some species of ryegrass and tall fescue are inoculated deliberately or infected with wild endophyte fungi. These fungi live within the plant in a symbiotic relationship where the plant provides the fungi with food and a place to live and the fungi provide the plant with protection from insect and nematode attack by producing toxic chemicals or mycotoxins which cause a disease in some grazing animals called a mycotoxicosis. So while the endophyte infected pastures are desirable from a pasture production perspective, the toxins they may contain can cause health problems for your horses. Horses grazing these pastures may exhibit some or all of the following clinical signs:

  • Reduced appetite
  • Weight loss or reduced growth rates
  • Inability to correctly regulate body temperature
  • Diarrhoea
  • Excitable, unpredictable, irritable or uncharacteristic behaviour
  • Over-reaction to common stimulus they would normally be OK with
  • Muscle twitching or twitching of the face, lips and eyelids
  • Prolonged pregnancy and thickened or retained placenta
  • Aborted or small, ‘undercooked’ foals
  • Dramatically reduced milk production by mares in early lactation
  • Loss of coordination, especially in the hind end, and staggering
  • Severe lameness
  • Bleached and/or rough coat

These possible symptoms are obviously very broad and many of them can be caused by any number of other factors, so you need to be very, very careful not to jump to conclusions and assume that the problems you are seeing in your horses are caused by mycotoxins in your pasture. if you have ruled out other possible causes and your horse is grazing a pasture that is potentially ‘poisoning’ them, then chances are what you are seeing is a mycotoxicosis.

WHICH MYCOTOXINS ARE PRESENT IN PASTURE?

Potentially, there could be any number of mycotoxins in your pasture as common moulds or fungi like Aspergillus, Fusarium and Penicillium can produce mycotoxins when growing on pasture. However, the mycotoxins most likely present in perennial ryegrass and tall fescue pastures that will cause issues are ergovaline and lolitrem B.

WHAT ARE MYCOTOXIN BINDERS?

A mycotoxin binder is a compound that can be added to a ration in an attempt to grab hold of a mycotoxin that may be present in feed or pasture, binding it strongly enough to prevent absorption from the gut of the animal.

There are many materials that can be used as mycotoxin binders including activated carbon, aluminosilicates like zeolite, cellulose, polysaccharides that are found in the cell walls of yeast and some bacteria (eg glucomannans) and even some synthetic materials.

DO ALL BINDERS BIND ALL MYCOTOXINS?

In a word… NO! And this is where a major key lies to whether mycotoxin binders will work to prevent pasture associated mycotoxin poisoning or not. For example, it has been shown that glucomannan from the yeast Saccharomyces cerevisiae is very effective at binding aflatoxin (one of the most important and prevalent mycotoxins present in grain based livestock feeds) and good ability to bind the fumonisin and zearalenone mycotoxins, but it is ineffective when it comes to binding other important mycotoxins like T-2 (trichothecene), DON (deoxynivalenol) and ochratoxin.

WHY DON’T ALL BINDERS WORK ON ALL MYCOTOXINS?

One of the reasons some binders can bind some mycotoxins and not others is dependent on the mycotoxin itself and whether it is polar (possessing an electrical charge) or not. Aflatoxin for example is a polar mycotoxin and is very easily ‘picked up’ by a yeast derived glucomannan based binder (which are the most common mycotoxin binders on the market for horses). The pasture based mycotoxins ergovaline and lolitrem B on the other hand are non-polar (no charge) so trying to pick them up with a yeast cell wall based toxin binder is sort of like trying to pick up a piece of paper with a magnet … it just won’t work.

WHERE DOES THAT LEAVE US WITH PASTURE MYCOTOXINS?

Well… unfortunately there is very little research to show what may or may not work with regards to pasture toxins. None of the companies that manufacture or sell the yeast based binders have (from what I can see) ever released data to show their products are effective against lolitrem B and ergovaline in any animal species, let alone horses. Research at the University of Melbourne is showing promising results with a new toxin binder in reducing the impact of ergovaline and lolitrem B in sheep. This toxin binder as well as one or two others now on the market for the more common mycotoxins are a new type of ‘binder’ that combines the ability to bind mycotoxins with the ability to also break them down and deactivate them – presumably it is this double mode of action that is enabling them to be somewhat effective in reducing the impact of the endophyte toxins like ergovaline and lolitrem B.

WHAT DO YOU DO NOW?

If you believe your horse is affected by pasture mycotoxins and you are using a mycotoxin binder it would be a good idea to contact the company you are buying the binder from and asking them what the binder is and whether they have data to show it actually binds the endophyte mycotoxins affecting your horse. If it is a yeast based binder it is unlikely to be reducing the effects of ergovaline and lolitrem B but you may still be seeing a positive effect if your other feed, hay or chaff is contaminated with one of the common mycotoxins that these yeast based binders are good at binding.

Really the best way to reduce the impact of ergovaline and lolitrem B is to either remove the horses completely from the pasture, especially during late summer and autumn when endophyte mycotoxin levels are likely to peak. Alternatively, manage your pastures well by preventing both overgrazing and underutilisation of pasture (allowing pastures to go rank/long with many seed heads) so that the risk of ergovaline and lolitrem B ingestion is reduced. Providing mycotoxin free hay to reduce pasture intake will also help.

 

Dr. Nerida Richards is FeedXL’s resident equine nutrition specialist. With a degree in Rural Science, a doctorate degree in equine nutrition and nearly 20 years of full time, on the ground experience in feeding all types of horses Nerida is able to help FeedXL members solve any problem they may come up against with feeding their horses. To learn more about Nerida and to ‘meet’ the rest of the FeedXL team, check out our About Us page here.

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