Malcolm Green of British-based horse supplement company EquiFeast looks at the use of magnesium and other “brain-impairing” chemicals in horse feeds.
Quiz: If someone put salt in your coffee what would you do?
1. Add loads of sugar
2. Add more salt and Bovril and turn it into a savoury drink
3. Throw it away and start again without salt
It’s a no-brainer, isn’t it? It can be very difficult to overcome a fundamental flaw in your horse’s diet by adding more stuff. Yet that is exactly what thousands of riders do every day without realising it. They feed diets with brain-impairing chemicals in them and then pile in more brain-impairing chemicals (marketed as calmers) and expect the world to be all honey and roses. Our approach is different from many other feed companies.
So what are these brain-impairing chemicals in our horse feeds?
Seems innocuous enough, doesn’t it? In days gone by it made sense to add magnesium to magnesium-deficient cereal-based feeds. Few people feed their horses like that anymore and high fibre/forage diets have plenty of magnesium in them1.
Oral magnesium is a sedative 3,4,5,6,7,8. The biochemists tell us how it sedates and the equine scientists have recently shown a comparable effect to the veterinary drug Acepromazine (Sedalin) 4,5.
Magnesium is poorly regulated in the body 7,8,13. The pro-magnesium lobby tells you the more you feed the more is excreted in urine and faeces. That is true but it explains only a proportion of the extra magnesium. In the experimental diets of Hintz & Schryver9,10 the more they fed the more was retained. And the retained portion is bigger than either of the excreted ones. Here is the graph from their 1972 paper. Pretty clear isn’t it?
Academics have looked at adding magnesium with no behavioural benefits reported5. Facebook threads report some horses getting on well with magnesium and others the reverse.
We have been monitoring customer feedback on magnesium’s effect on horses since 2011. Obviously, this is anecdotal but these are our conclusions:
- Horses don’t seem to overdose on the naturally occurring magnesium in grass and hay (mostly bound to the chlorophyll molecule). Have millions of years of evolution sorted this out? Hintz & Schryver speculated on this but never tested it experimentally10.
- Artificial sources of magnesium used in feeds and supplements seem to elevate blood magnesium levels and cause problems for the brain. Hintz & Schryver demonstrated this9,19.
When we start our client’s horses on “no artificial magnesium diets”, 97% stick with that11.
Sugars and starches
The vast majority of the horses that are referred to us are already on modern high-fibre diets though there can be a lot of starch and sugar in some pasture and hay and some conditioning feeds.
We try to get sugars and starches down in diets – more because of the negative impacts on ulcers, colic and laminitis than for the behavioural issues. There is evidence that, except for the hardest working horses, who may need some carbohydrates for glycogen replenishment after very hard work, modern high fibre, high oil diets are very capable of producing top-quality performances12.
GABA agonists and other herbal ingredients
Sorry that this sounds rather technical but if I list a bunch of them for you, you will probably find most of them quite familiar: chamomile, devil’s claw, eugenol (active ingredient in aniseed, fennel and licorice), hops, kava kava, lavender, passionflower, rauwolfia, skullcap and valerian.
But you will probably be very surprised when I tell you that the GABA agonist you have probably heard of most is Diazepam (Valium). There are several herbal feed and supplement products on the market in the UK and Europe that hit the same receptor in the brain as Valium.
In North America, the US Equestrian Federation has every one of those listed above on its prohibited lists. Some are already on the FEI prohibited substances list as well. Evidence that for some horses they work, perhaps?
Our view is that, though some horses respond well to these herbal drugs, our approach is to improve brain function rather than dampen it down so we try to eliminate them from diets.
Why is brain function so important?
We have all read the idea that, because they are prey animals, horses should be naturally nervous and spooky. I don’t feel comfortable with that argument. To me, horses should be good at assessing the risks in their environment. I think a horse that can’t tell the difference between a sparrow and a lion or that spooks at the whiteboards is more likely to run into trouble than to keep safe. So our approach to having a calm horse is not to dampen down the spook response – as magnesium does4 – but to do our very best to get the brain working as well as possible.
Once that is achieved our horses can realise that there are very few apex predators in Britain. And then they learn to concentrate on their rider and their work without fear or tension. Every rider’s dream.
Nutrients that are required for good brain function
Eliminating brain impairing nutrients is the first part of our whole diet approach to horse behaviour and function. For a lucky few that is all that needs to be done. But there are nutrients that are either in short supply in modern diets or that get used up rapidly during stress or excitement that seem to benefit many horses when used correctly. But that is a topic for another article.
» Further reading: No Added Magnesium Diets
References and further explanations
1 Comparing the magnesium levels in forages from the National Research Council with its recommended levels of dietary magnesium shows that the only forage that won’t meet the horse’s needs are corn cobs. Most forages would provide 2-3 times the RDI if they were fed as 100% of the diet. During spring and autumn rapidly growing, rich, fertilised pasture may lead to short-term magnesium deficiencies as Mg is lost in the urine as a result of the horse’s efforts to excrete excess potassium2.
3 The FEI Prohibited Substances Database has injectable magnesium on its Controlled Medication list as a sedative and that begs the question “Can ingested magnesium have the same effect as an injection?” Nobody has done that experiment but Jess Dodds and Wendy Pearson have shown that oral magnesium has the same effect on horses as the veterinary sedative Acepromazine (Sedalin).
4 Magnesium aspartate supplementation and reaction speed response in horses: Abstracts/Journal of Equine Veterinary Science 35 (2015) 401-402.
5 Pearson et al. Journal of Equine Veterinary Science 51 (2017) 86-91
6 Wilkins and Wilkins. The role of calcium and comparable cations in animal behaviour 2003; Royal Society of Chemistry
7 Jahnen-Dechent and Ketteler, Magnesium Basics. Clinical Kidney Journal, 2012 Feb; 5(Suppl 1): i3-i14.Oxford University Press
8 Magnesium Disorders in Horses. Vet Clin Equine 27 (2011) 149-163
9 Magnesium Metabolism in the Horse, Hintz and Schryver. Journal of Animal Science, vol 35, no 4, 1972
10 Magnesium, Calcium and Phosphorus metabolism in ponies fed varying levels of magnesium. Hintz & Schryver, Journal of Animal Science, vol 37, no 4, 1973
11 Evaluation of our confidential sales figures for Core & More feeds and balancers
12 Pagan et al. Effect of non-structural carbohydrate intake on glycogen repletion following intense exercise. Journal of Equine Veterinary Science vol 35, iss5, May 2015 408-409.
13 Concentrations of ionised and total magnesium and calcium in healthy horses: Effects of age, pregnancy, lactation, pH and sample type. Berlin and Aroch. The Veterinary Journal 181 (2009) 305-311