Magnesium based calmers are by far the most common in the equine supplements market, yet experience from client feedback tells us that magnesium fails in far more horses than they help. A small trial we conducted in 2008 suggested that magnesium calmers will only work in approximately 25% of horses – a pretty high failure rate!

So, why are magnesium calmers the market leaders? Probably because they work better than the other calmers on the market based around ingredients such as tryptophan, B group vitamins and herbs. Surely there must be something more effective? Here is five top myths about magnesium…

 1)      ‘Your horse is deficient in magnesium…’ This is myth number one! The National Research Council of America (NRC) publishes a book called the “Nutrient Requirements of Horses”, this is the equine nutritionist’s BIBLE. Of the 103 listed ingredients, only corn cobs, bread waste and oils don’t provide the recommended daily Allowance (RDA) for magnesium.

When we look at analysed grass and hay the reports show even low magnesium pastures and hay contain the RDA comfortably as far as horses are concerned. Most feed ingredients provide multiples of the RDA. So why do so many feed companies add extra mag?

2)      ‘Magnesium doesn’t have a bad effect…’ This is myth number two! Magnesium is a sedative. It has been used in anaesthesia in both horses and humans for decades. How magnesium causes sedative effects is pretty well understood. By blocking certain channels and calcium receptors, effectively magnesium prevents normal switching on of cellular processes. When this happens in the brain, the horse is sedated; think of it as a type of chemical brain impairment.

Whilst some horses sedate quite nicely the feedback we have from thousands of customers is that brain impaired horses are often more anxious, more spooky (though they flee slower), often hyper-alert and struggle to concentrate. It is because of these issues, injectable magnesium is on the FEI’s controlled substances list.

Click HERE  to read about a study conducted in Australia linking magnesium to sedation. 

3) ‘Magnesium based calmers always help with unwanted behaviours…’ Myth number three! On the market there are a plethora of magnesium based calmers however experience from client feedback tells us that magnesium fails in far more horses than it helps. In fact a small trial was conducted in 2008 suggesting that magnesium calmers only work in approximately 25% of horses – a pretty high failure rate don’t you think? Click HERE to read about a Canadian study that showed the physiological dampening effect of magnesium compared to a sedative that didn’t produce any of the benefits riders would want to see from a calmer.

Click HERE to read Jacqueline Helme’s research on the effect of magnesium on horses. 

4) ‘If diets are high in calcium, magnesium absorption is impaired leading to a risk of deficiency…’ Although this myth is number 4 it is no less important than number 1!Experiments carried out by the Americans Hintz & Schryver way back in 1972 and 1973 make it very clear that the balance between calcium and magnesium in the diet of horses does NOT affect the absorption of magnesium. Please Click HERE to see further information about magnesium absorption.

5) ‘Excess magnesium ingested is simply excreted in the droppings or the urine…’ The final myth. Hintz & Schryver looked at this too! It is clear from their work that whilst excretion of magnesium increases as the diet level increases, it doesn’t do so enough. The more magnesium you feed, the more is retained in the body and specifically in the blood.

From this we understand that magnesium needs to be used with great care! All this said we do understand that some horses benefit from a small about of supplementary magnesium; this can be a fine line. We just have to strike the right balance!

In Summary

Magnesium needs to be used with great care as a ‘calmer’. Too much and you run the risk of sedation, which as we understand can result to some negative behaviours.

Equally, we do understand that some horses can benefit from a very small amount of supplementary magnesium in the diet. The tricky part comes from an increasing trend for feed companies to add magnesium in to their cubes, mixes, chaffs and balancers – making it incredibly difficult to quantify exactly how much supplementary magnesium your horse is getting.

As a result of this, we are finding customers are finding our diet reviews increasingly helpful in determining if their horse is actually on a high magnesium diet which is causing poor behaviour, or if the dietary magnesium levels are actually within our optimum range – meaning their horse would potentially benefit from using a magnesium free behavioural supplement such as chelated calcium.  


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