Magnesium may not consistently influence reaction speed

Horses have evolved to run away in the face of danger. While this may keep them safe from predators, it can be dangerous in a domesticated setting. 

Magnesium is often included in supplements to calm nervous or excitable horses. However, recent research raises doubts over whether it is effective.

A 2015 study* in a group of Standardbreds gave backing to the suggestion that magnesium could slow reaction times. The study used magnesium aspartate, a readily available source of magnesium. Aspartate itself acts as a neurotransmitter and questions have been asked about whether it was the magnesium or the aspartate that was responsible.

To investigate further, and to see whether the original findings could be repeated in other breeds, Dr Glenys Noble and colleagues at Charles Sturt University in New South Wales, Australia conducted another study in collaboration with WALTHAM® Equine Studies Group. 

Eighteen animals (6 ponies, 6 Arabians and 6 Thoroughbreds) were fed three different diets over seven days in a random order. The diets comprised:

• a control hay-based diet providing the National Research Council’s recommendations for magnesium;
•  the control diet plus the same amount of supplementary magnesium (10g/500kg horse) as magnesium aspartate;
• or the control diet plus the same amount of supplementary aspartate (provided as sodium aspartate).

Some animals decreased their reaction speed and others increased it when fed the magnesium aspartate or the sodium aspartate, compared to showing no significant effects when fed the control diet.  At no time did the horses demonstrate any characteristics of being either sedated or more excited when being fed the diets. The research team concluded that neither the magnesium nor the aspartate had a consistent effect.

Clare Barfoot RNutr, the research and development manager at SPILLERS® commented: “As it stands these results suggest that magnesium supplementation cannot be relied on to modify horses’ reaction speeds. It may be wiser to focus on training and habituation to stressful situations to help manage reactive behaviour, rather than to rely solely on magnesium-based products.”

*Journal of Equine Veterinary Science

Volume 35, Issue 5, May 2015, Pages 401-402

Magnesium aspartate supplementation and reaction speed response in horses

J.A.Dodd, G.Doran, P.Harris, G.K.Noble

https://doi.org/10.1016/j.jevs.2015.03.051