We often get asked why our calmers don’t contain magnesium, and the answer is simple. Scientific evidence for its use as a calming ingredient is incredibly limited, and most studies that have investigated this have come up with inconclusive results. Magnesium deficiency is rare, and horses don’t generally need to be supplemented with it. In a 2018 study, a shocking 59% of participants thought that magnesium had the biggest calming influence compared to other ingredients.
Why would Magnesium have calming benefits?
The myth that magnesium is calming likely stems from its role in muscle and nerve function. Anecdotally, magnesium is often claimed to have this calming effect due to its ability to relieve muscle tremors and nervousness. Ultimately, the connection between nerve function and temperament is a weak link, with little to no scientific evidence existing to support the theory. There is evidence to suggest that magnesium and boron might have a beneficial effect on headshaking in horses, however, it is important to note that headshaking is a nerve disorder and not a behavioural issue. Magnesium, whilst an important mineral for many other functions within the body, is yet to be proven as a calming ingredient.
What does the research say?
Let’s take a look at some of the research that has investigated the impact of magnesium on temperament…
Dodd, J. (2021). Investigating the impact of oral magnesium aspartate on behaviour, flight reactivity and mineral metabolism in horses. [Masters Thesis, Charles Sturt University]. Charles Sturt University.
Three breed types were supplemented with 11g oral magnesium aspartate per day, and their reactivity to novel stimuli was measured, with reaction speeds being recorded. The results showed that, across the three breed groups, magnesium had no significant impact on reaction speed despite small changes being noted. Though there were small reductions seen, 11g per day of magnesium aspartate equates to around 140g normal magnesium - significantly higher than what you’d find in most supplements.
Nielsen, B.D. and O’Connor-Robison, C.I. (2014) ‘A pilot study to determine if a dietary mineral supplement can affect reactivity to stimuli by horses in training’, Comparative Exercise Physiology, 10(3), pp. 159–165. doi:10.3920/cep140006.
Fourteen horses were given a calcium and magnesium-rich supplement and subjected to both a novel object test and a handling reactivity test. Horses were equipped with heart rate monitors, and handlers were blind as to whether the horse had been given the real supplement or a placebo. There were no significant differences in heart rate or reactivity between horses who received the supplement and those given the placebo, so the results of the study were deemed inconclusive.
Thomson-Parker, T.L. et al. (2023) ‘Impact of oral phytozen EQ supplementation on plasma cortisol and behavior responses of young horses exposed to stressful stimuli’, Journal of Equine Veterinary Science, 127, p. 104828. doi:10.1016/j.jevs.2023.104828.
This study looked at whether a supplement containing a blend of citrus botanical oils, magnesium, and yeast would reduce startle responses and signs of stress in 14 young horses. Horses were split across two groups; one receiving the treatment, and the other the control group (i.e. not receiving the treatment). Horses were tested for travel speed when startled, and stress responses when tied or trailered in isolation. The study did find that there was a significant decrease in travel time during the startle test for the treatment group, however there was no difference in stress response across the two groups. Again, these results are inconclusive.
As you can see, the research is limited. It is important to note, that results are considered significant after statistical testing of the results to find a number called a P-value, which must be higher than 0.05 for the results to be deemed significant. Not significant = not proven.
Because no research has been able to support the use of magnesium as a calming ingredient, no research into optimal doses has been undertaken. So, if you are using a calmer containing magnesium, a) it hasn’t been proven to work, and b) if it does work, we have no idea how much the horse needs for it to have an effect. Choose calming supplements that have undergone clinical trials and contain ingredients that the research does support.
So, in conclusion, it’s probably best to stay away from this marketing myth until magnesium has been proven to work. If it ever is, of course.
References
Dodd, J.A. et al. (2015) ‘41 magnesium aspartate supplementation and reaction speed response in horses’, Journal of Equine Veterinary Science, 35(5), pp. 401–402. doi:10.1016/j.jevs.2015.03.051.
Dodd, J. (2021). Investigating the impact of oral magnesium aspartate on behaviour, flight reactivity and mineral metabolism in horses. [Masters Thesis, Charles Sturt University]. Charles Sturt University.
Marlin, D.J. (2018). ‘Owner Reported Perception of the Efficacy of Equine Calmers Commercially Available in the UK’, Department of Physiology, Oklahoma State University.
Nielsen, B.D. and O’Connor-Robison, C.I. (2014) ‘A pilot study to determine if a dietary mineral supplement can affect reactivity to stimuli by horses in training’, Comparative Exercise Physiology, 10(3), pp. 159–165. doi:10.3920/cep140006.
Ross, D.J. and Roberts, J.L. (2018) ‘Equine calming products: A short survey into their use, effect, and knowledge using a small sample of horse owners in the north of Scotland, UK’, Journal of Equine Veterinary Science, 68, pp. 63–67. doi:10.1016/j.jevs.2018.05.208.
Sheldon, S.A. et al. (2019) ‘Effects of magnesium with or without boron on headshaking behavior in horses with trigeminal‐mediated headshaking’, Journal of Veterinary Internal Medicine, 33(3), pp. 1464–1472. doi:10.1111/jvim.15499.
Thomson-Parker, T.L. et al. (2023) ‘Impact of oral phytozen EQ supplementation on plasma cortisol and behavior responses of young horses exposed to stressful stimuli’, Journal of Equine Veterinary Science, 127, p. 104828. doi:10.1016/j.jevs.2023.104828.