An internet search or visit to your local feed store will lead to an array of calming supplements. Although magnesium based supplements have been a popular choice for many years, there is very little scientific evidence to support their use. Whilst initial research conducted in collaboration with SPILLERS produced some promising results, a follow-up study suggests that magnesium may not reliably modify behaviour after all.

Previous research

A small study published in 2015 found that feeding 10g of supplementary magnesium in the form of magnesium aspartate (a very available source of magnesium) could significantly reduce reaction speed. However it was unclear whether it was the magnesium or the aspartate, an amino acid (building block of protein) which acts as chemical messenger that was responsible.

What is reaction speed?

Horses are prey animals and evolved to take flight under times of stress – a trait that many horse owners feel only too aware of! However assessing behaviour can be subjective so in order to conduct a scientifically fair test, a method of reliably and consistently measuring the effect (if any) of feeding supplementary magnesium was required. In both studies, reaction speed was therefore measured as the time taken to travel a set distance after being startled using a previously approved protocol.


New research conducted in collaboration with SPILLERS

To test whether the results from the previous study could be repeated and if so, whether it was the magnesium or the aspartate that was responsible, 6 Thoroughbreds, 6 Arabs and 6 ponies were fed 3 different diets for 7 days in a random order:

  • The base diet only, which consisted largely of hay and exceeded daily magnesium requirements
  • The base diet plus magnesium aspartate (the magnesium aspartate provided 10g of magnesium as per the original study)
  • The base diet plus sodium aspartate (at the same level as the previous study)


Reaction speed was measured on day 1 and day 7 of each feeding trial.


The results

  • Overall there was no significant effect of feeding either magnesium aspartate or sodium aspartate on reaction speed.
  • No horses showed any signs of being either sedated or more excited when fed the magnesium aspartate or sodium aspartate.


What does this mean?

This new research suggests that magnesium may not reliably modify behaviour. With this in mind, focusing on training and habituation may be more effective than turning to a supplement.


Do you feed a magnesium supplement to your horse? Share your experiences in the comments section below!