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 – you will find links to the science from other articles in this section. A horse’s Recommended Daily Allowance (RDA) of magnesium can depend on a range of factors. We have summarised 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 well in  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. In this article, Malcolm Green describes how to create a diet with little or no added magnesium in an Australian 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 unnecessarily large quantities of other minerals generally not needed and possibly counter-productive in parts of the UK such as iron and manganese.

Formulated feeds are designed to be fed at a certain rate – often 3-4 kgs a day for a 500kg 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 250-500 grams per day. Or a supplement that may be in the region of 20-50 grams per day.

Balancer options

In the UK most balancers are of the feed variety. They enable you to make up your own diet from pasture, hay (various options) and various other ingredients we will discuss below.

At EquiFeast UK, our most basic feed balancer is called:

  • EssentialCORE - Contains no added magnesium. But does contain the amino acids lysine and methionine, sulphur (MSM), zinc, copper, iodine, selenium and cobalt. Vitamins include A, D3, E, K, C, B1, B2, B6, B12 niacin, pantothenic acid, folic acid, biotin and carnitine. 

    To be honest the next product, CoolCORE, is far more popular.

  • CoolCORE  - This is simply EssentialCORE plus the chelated calcium from our famous Cool, Calm & Collected. This is by far our most popular balancer. 

  • CoolCORE itself comes comes pre-combined with a number of other products - DIGEST, BombProofing and WINNINGEDGE. Chat to one of our advisors or try our simple online CORE Selector.

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

This where our MORE range comes in.

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. 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 starting with:

MORE Fibre - Super fires and virtually NO starch or sugar.

Hays from grasses like Rhodes and “meadow hay” are probably the safest you can get. Good native grasses are also excellent.

Lucerne is a hay that people either love or hate. Generally it is intensively produced so can be very high protein and potassium but it can also be excellent to fill out the feed and make the meal a bit bigger (more for the benefit of the owner than the horse). Dengie and Honeychop both have excellent ranges of products with no added magnesium.

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.

Sunflower seeds are also high in slow release energy as well as protein and make excellent components of the diet. Balancing the omega 3 and omega 6 oils with some micronized linseed is a good idea. We use these in our MORE range.

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 (but still carbohydrate) energy component. Again it is wise to test out how your horse responds to lupins.

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 or at risk of laminitis, ulcers, colic etc.


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

If you need further help you can use a nutritionist.