Written by Malcolm Green, Technical Director, EquiFeast

Magnesium is an essential nutrient for horses, but the enthusiasm with which it is added to horse feeds defies all the science. Here is a link to a really easy-to-read review article that supports all of our research, trials and monitoring of horses over the past years. I have highlighted the key points so you can skip through to the important bits in seconds :)


A horse’s Recommended Daily Allowance (RDA) of magnesium can depend on a range of factors. We have summarized these below:

Weight of mature horse in work

Light work (grams per day)

Moderate work

(grams per day)

Heavy work

(grams per day)

Very Heavy Work

(grams per day)





















If this table does not apply to your horse, further information can be found in Nutrient Requirement of the Horses, 6th Edition, published by the National Research Council, 2007.

Grass, Lucerne and grass hay almost always contain excess of the recommended amount of magnesium for horses whatever their work load.

There are a number of reasons why we believe that the vast majority of horses do better with no added magnesium in their diet. For more information about our research you can access our magnesium articles here.

As we have got magnesium under control in our customer's horses that has highlighted another group of ingredients that also impair brain (and other organ) function. They come under the rather technical banner of "GABA agonists". Put simply these are mostly herb or amino acid ingredients that hit the same receptor as diazepam (Valium). For some horses this has dramatic and negative impacts on behavior. Others apparently sedate nicely on them (which is presumably why almost every SmartPak calmer has taurine in it). 

Because they "work" by reducing communication between brain cells they are doing the opposite of our objective (to get the brain and other organs to work as normally as possible). Thus they have no place used in conjunction with our products.

Apart from in calmers we are seeing more and more GABA agonists as flavorings in feeds, as painkillers and (rather naughtily because it is the painkilling characteristic that works) as joint supplements.

Many GABA agonists (drugs as well as "nutrients") are on the FEI prohibited substances list. The USEF has a much longer banned list and the EquiFeast list is longer still.

In this article, Malcolm Green describes how to create a diet with no added magnesium or GABA agonists in the North American market.


Making your own diet from “straights”

The only real benefit of formulated feeds is that they contain supplementary vitamins, minerals and sometimes other key nutrients. It is these premixes that nearly always contain artificial sources of magnesium. They may also contain other minerals generally not needed and possibly counter-productive in North America such as iron and manganese.

Formulated feeds are designed to be fed at a certain rate – often 6-10 lbs a day for a 1200 lb horse. Feed less and you under-supplement, feed more and you over-supplement. In the UK this has led to a dramatic increase in the use of “feed balancers”. These may take the form of a “feed” that is fed at 1/2 - 1 lb per day. Or a supplement that may be in the region of 1 - 2 ounces per day.

Formulated feed options

I have really struggled to find American feeds with no added magnesium (there are some exceptions on the West Coast listed at the bottom of this article). If you find a brand please let me know. Don't just believe the label or web site though. Many don't list the magnesium they add.

Balancer options

In America most balancers are of the supplement variety though some are pelleted. They enable you to make up your own diet from pasture, hay (various options) and various other ingredients we will discuss below. The only problem is the magnesium these products contain!

At EquiFeast, our balancers all contain no added magnesium, iron or manganese. But do contain the amino acids lysine and methionine, sulphur (MSM), zinc, copper, iodine, selenium, cobalt (racing legal quantities). Vitamins include A, D3, E, K, C, B1, B2, B6, B12 niacin, pantothenic acid, folic acid, biotin and carnitine. 

We are passionate that hooves are fundamental to a healthy horse so the package outlined above is designed to be strong enough to optimise hoof growth and quality in all but the most exceptional cirumstances.

From April 2021 this balancer package is available in USA pre-blended with Cool, Calm & Collected under the brand name Sensible Essentials. These are packed in our UK packaging and each pack contains enough for 5 weeks for a 1,200lb horse. There is a starter version of this to load the chelated calcium component.

We have recently expanded the number of balancers available in North America combined with different ingredients for different purposes like specific health issues, performance and Kissing Spines. Here is a selection:

  • LAM Essentials was initially targeted at IR, EMS and Cushing's but is becoming very popular with low magnesium diets for PSSM horses. There is a starter version of this to load the chelated calcium component.

  • FlexEasi combines our chelated calcium, full spectrum balancer and our proprietary mobility package. Though great for all sorts of slightly stiff horses we did trial it on horses with KS. There is a starter version of this to load the chelated calcium component.

  • WINNINGEDGE is a stronger version of FlexEasi with extra nutrients for stamina and immunity that is targeted at high performance horses. There is a starter version of this to load the chelated calcium component.


So what can you make the rest of the diet up with?

Our primary objective is to turn your pasture and grass hays into good horse feed. So unless your horse has a problem with these feeds, they will make the foundation of the diet. Hay rich in ryegrass, clover and even Lucerne are fine if your pasture is made of native grasses or meadow grasses. Even oxalate pastures will be fine so long as they are not too rich and fast growing. But if your paddocks are rich and growing fast you may need to be sourcing some low carbohydrate, high fibre hay to dilute it with. Or some of the “super fibre” options below.

Hays from grasses like Timothy, Rhodes and “meadow hay” are probably the safest you can get. Good native grasses are also excellent. Some people are using Teff hay. This is low in carbs but does contain oxalates. Our chelated calcium seems to be the most effective antidote against the issues that oxalate create making Teff an acceptable forage under out regime.

Lucerne is a hay that people either love or hate. Generally it is intensively produced so can be very high protein and potassium. For most horses it is fine as a supplementary feed.

Oaten Hay will normally have a lot of the oat grain left on it. That makes it higher in starch. But oats have been a traditional feed for horses for centuries and there is evidence that, compared to other cereal grains, it is much safer and indeed may have some physiological benefits.

For more concentrated fibre sources consider beet pulp and Copra. Both contain what are becoming known as “super fibres” which are more digestible than grass fibre but also appear to boost the digestibility of the fibre in pasture and hay. So they provide a double whammy. A few people report their horses going a bit loopy on copra so test it out gently.  UPDATE FEBRUARY 2021 - There is some anecdotal evidence that the relatively high level of oxalate that some beet pulp products contain is contra-indicated if pastures or hay are also high in oxalates. 

Rice bran is also becoming quite popular though the starch level is a little higher. Whilst on the topic of starch I have noticed the American horse feed industry seems to have invented the term "controlled starch". Please do not think this means low starch. It doesn't!! In Australia we have found some Rice Bran products that are very high in magnesium and that seem to cause problems as a result. So we are less enthusiastic about this material than we used to be.

Sunflower seeds are also high in slow release energy as well as protein and make excellent components of the diet. They do need to be crushed if they are not to pass straight through undigested. Balancing the omega 3 and omega 6 oils with some micronized linseed is a good idea.

Another protein boosting option is from pulses. I’m not a great fan of soya (quite starchy and too many phyto-oestrogens) but lupins claim to have a much better non-starch energy component. I'm not sure how available they are in America. They are very popular in Western Australia.

The feeds above offer a broad range of fibre, energy and protein options enabling horse owners to adjust their diet whether their objective is to build condition or muscle or just provide energy and protein to maintain horses for work.

They also provide plenty of low starch, high fibre options to help manage horses with EMS, PSSM, Cushing’s, PSSM or at risk of laminitis, ulcers, colic etc.

Other supplements

We can now make almost all of our UK made supplements available in the USA. We have excellent products for immunity, infections and allergies and digestion in addition to the products mentioned in this article. These products are all designed to be compatible with each other. No unnecessary duplication of nutrients and, in the vast majority of circumstances, no gaps either.



Formulating a diet using a variety of different “straights” supplemented with a balancer (like EquiFeast’s Sensible Essential) will provide all the options you need to formulate a feeding routine suitable for your horse.

If you need further help feel free to contact us

A list of USA and Canada feed forms that apparently don't add magnesium to their grains (not verified by EquiFeast).

Please let us know if you find more companies but don't rely on labels or websites. There is no legal obligation to list added magnesium on those and most firms don't:

Standlee Premium Products (a large range of chaffs and pellet forages)
22349 Kimberly Road, Suite E
Kimberly, ID 83341

208-825-5117 Office
800-398-0819 Toll Free
208-825-5119 Fax


Coolstance (for Copra): https://stanceequitec.com/

Renew Gold Equine (for Rice Bran): https://renewgold.com/products/renew-gold-equine-products/

New York:
Narrowsburg Feed and Grain, NY Tel: +1 845-252-3936

In the West:

Ellenbass Feeds https://www.elenbaasco.com/product-category/equine/

Haystack Farm & Feed, 541 475-2319. https://haystackfeeds.com/