Magnesium for Horses Supplement to Avoid Laminitis

Why do horses need supplemental magnesium? Magnesium is needed directly for over 350 biochemical processes within the body, and is additionally involved in thousands of others. Magnesium is vital for energy production, metabolism of other minerals, regulation of blood sugars, maintaining normal muscle and nerve function, as well as strength of bones and teeth. The development of laminitis (also termed founder) is inflammation of the laminae of the foot – the soft tissue structures that attach the coffin or pedal bone of the foot to the hoof wall. It can be a direct result of magnesium deficiency. Magnesium for horses is essential for hoof health, calm temperament, flexibility and better performance for working horses.

Magnesium for HorsesLow Magnesium in the Soil Means Low Magnesium in Feeds

The majority of readily available horse feeds and forages are grown commercially with the help of fertilizers that contain little or no magnesium. Over time, soils become depleted of magnesium and some other minerals, which are then not available for uptake by the growing plants. The result is an over-abundance of minerals such as phosphorous and potassium and a deficit of magnesium. Some legume forages such as lucerne and clover are naturally high in calcium but will be low in magnesium if grown in magnesium deficient soils. High levels of calcium, phosphorous or potassium inhibit absorption of the small amount of magnesium that may be present in the forage. In many countries, regions with naturally acidic soils are likely to have low magnesium levels; horses grazing such pastures may need supplemental magnesium.

The ideal environment in which equines thrive includes vast areas of low-sugar native pastures on which to freely roam in their daily search for feed and water. The reality is that domestic horses are frequently kept on pastures that were previously used for dairying and/or cattle production. These pastures were often ‘improved’ by the addition of imported grass species which can accumulate a very high sugar content, suitable for achieving high milk yields and rapid growth in cattle. It has been well documented that the equine digestive system is not adapted to processing large amounts of sugar or non-structural carbohydrates (NSC). Horses grazing high NSC pastures become susceptible to blood sugar disorders such as insulin resistance, which can result in footsoreness or laminitis and poor hoof quality. High levels of blood glucose, from a diet high in sugar/NSC, increases the body’s need for magnesium but at the same time will cause magnesium to be excreted through the kidneys and urine, thus magnifying any existing dietary magnesium deficiency.

Medical Nutritionist Dr N Campbell-McBride states that 56 molecules of magnesium are needed to metabolise each molecule of sugar that humans consume. If the same ratio applies to equines, it is not hard to see why horses consuming high-sugar grasses or feeds require large volumes of magnesium to metabolise that sugar.

Consequently many horse owners have been forced to remove their horses from all pasture, or at least have grazing limited to one or two hours per day. Some have established a ‘track’ system where a narrow track around the perimeter of a paddock is fenced off, and most of the grass either killed or grazed down to virtually nothing. This has been an expensive and time-consuming solution as pasture must be replaced by hay.

What are the Signs of Magnesium Deficiency?

As magnesium is needed for such a wide range of body processes, deficiency signs can present in an equally wide range of ways. Ten horses living in the same paddock may show signs of magnesium deficiency in ten different ways, influenced by individual genetic traits that govern how much magnesium can be absorbed and how much is excreted.

Some common signs of magnesium deficiency may include:

∗ Nervous, anxious temperament
∗ Sudden shying at familiar objects
∗ Violent pulling-back when tied
∗ Dislike of grooming
∗ Aggression towards owners or herd-mates
∗ Separation anxiety, herd-bound
∗ Restless under saddle, unable to focus on rider, bucking
∗ Poor hoof quality, footsore without shoes or boots on hard or rough ground
∗ Short stride with inappropriate toe-first hoof landing in movement
∗ Laminitis
∗ Grass belly
∗ Insulin resistant with heavy crest
∗ Stiff, braced posture with deep ‘V’ behind withers
∗ Front feet placed far back under body when resting
∗ Tight, sloping croup
∗ Stifle catch
∗ Tying-up
∗ Excessive sweating in hot weather, shivering in warm, wet weather
∗ Dry, flaky skin, Sweet-Itch, Qld Itch, Watery eyes

It has now been found that some horses are able to remain permanently on pasture with no restrictions to grazing, even those highly prone to laminitis. This has been achieved by feeding magnesium to those horses in sufficient amounts to counteract the effects of a high sugar intake.

As well as a high consumption of sugar, stress of any kind will cause large amounts of magnesium to be excreted. This would include travel, changed living or herd environment, extremes of heat and cold, injury, pain, even the physical exertion of exercise. Very few domestic horses would consume enough magnesium from pasture or feeds to meet their daily needs, and have sufficient magnesium stored in body reserves to counter the amount lost each day.

The link between magnesium deficiency and insulin resistance There appears to be a clear connection between lack of cellular magnesium and metabolic problems such as insulin resistance (IR). The Magnesium Factor (details below) is a book co-authored by Associate Professor Mildred Seelig that contains a wealth of information about the role of magnesium in human health. For those who like to see the detail, there are 75 pages of references. Dr Seelig was both a practicing physician and researcher who devoted some 40 years to investigating magnesium; she was a President and Executive Director of the prestigious American College of Nutrition and founding editor of its Journal.

The chapter on ‘Metabolic Syndrome X, Diabetes and Magnesium’ includes reports on research done by Prof Lawrence Resnick and colleagues at Cornell who concluded that a low magnesium ion inside cells causes metabolic syndrome. Quote from p.41:

“As a cell’s magnesium ion level falls, the calcium ion level rises. The result is a low magnesium/high calcium cell ratio. This affects the functioning of various kinds of cells in ways that bring on syndrome X “

A chart then follows that lists the consequences of low magnesium/high calcium for cells in the pancreas, fat tissue, muscle, blood-vessels, blood platelets, heart muscle, adrenal glands, nerves, liver and kidneys.

Magnesium deficiency has been reported to result in insulin resistance by other researchers. Some studies have been done to investigate the role of insulin resistance in magnesium transport, concluding that insulin resistance and magnesium depletion ‘may result in a vicious cycle of worsening insulin resistance and decrease in intracellular Mg(2+) which may limit the role of magnesium in vital cellular processes’. (Reference source below)

Numerous horses displaying external signs of insulin resistance such as a cresty neck and localised fat pads around the withers and tail-head have been observed to lose those external signs of IR within a few weeks of commencing magnesium supplementation.

Fructan and the Risk of Laminitis

Much publicity has been given to the risk for laminitis in horses grazing high-fructan pasture or hay. Fructan is the form in which energy is stored in C3 plants growing in cool-season climates. In warm-season regions C4 plants store energy as starch, not fructan. However, owners of horses grazing non-fructan pastures in warmer regions such as Queensland will verify that their horses are just as susceptible to laminitis and hoof problems as horses grazing fuctan-rich pastures in cooler regions. A sore foot is a sore foot, regardless of the diet of the horse that owns it.

Some fascinating research has been done recently by Prof Richard Johnson that indicates both fructan and starch can be metabolised to fructose by gut bacteria, suggesting that it is fructose that is ultimately the cause of weight-gain and obesity in both horses and humans. The rapid breakdown of fructose by the enzyme fructokinase in the liver, small intestine, caecum and large intestine etc causes ‘cell shock’, a brief period in which the cells become depleted of ATP energy. This leads to the production of oxidants, and systemic inflammation via bacterial products entering the blood, and could be implicated in the cascade of biological events that lead to founder.

It would be interesting to know if supplemental magnesium is able to assist in reducing or preventing the depletion of ATP energy consequent to the action of fructokinase on fructose produced from ingested fructan and starch. Some work has already found that dietary magnesium may prevent fructose- induced insulin insensitivity as indicated in this study: Dietary magnesium prevents fructose-induced insulin insensitivity in rats. TW Balon, A Jasman, S Scott, WP Meehan, RK Rude and JL Nadler Department of Diabetes, Endocrinology, and Metabolism, City of Hope National Medical Center, Duarte, CA 91010.

If proved to be correct, this could perhaps explain why horses grazing C4 fructan-free grasses that accumulate starch appear to be just as vulnerable to laminitis and hoof problems as horses grazing C3 fructan accumulating grasses; they both have the potential to be metabolised to fructose by gut bacteria.

Visible improvements to hoof structure and function generally commence within a couple of months.

Research is needed to determine if hoof lamella cells could be added to an equivalent equine list of the consequences of low cellular magnesium, on the basis that low magnesium/high calcium may disrupt magnesium-dependent ATP production, resulting in a weakened lamella connection. This may be different from what is conventionally thought of as ‘laminitis’.

The metabolic pathway through which magnesium could be involved is in the essential production of ATP energy within all cells, including hoof lamella. Magnesium is needed directly for over 350 biochemical processes within the body, energy production being foremost. Many sources designate ATP as MgATP because ATP must be bound to a magnesium ion in order to be biologically active. Neurosurgeon Russell Blaylock has described the importance of maintaining cellular energy in protecting neurons from exposure to toxic substances, and the role of magnesium in limiting cell damage from the influx of excess calcium.

Magnesium for Horses – Which Kind?

Many different forms of magnesium are available for horses, ranging from very expensive chelated organic magnesium products to cheap inorganic raw materials.

Magnesium chloride is a very good source of magnesium as it is easily absorbed by the body. Other forms of magnesium, such as magnesium oxide, magnesium hydroxide and others, must be broken down in the stomach by hydrochloric acid to form magnesium chloride. Feeding magnesium chloride eliminates the need for breakdown in the stomach which results in a much higher absorption rate. A study was done to compare absorption rates of various types of magnesium supplements; it was found that magnesium chloride had a high bioavailability rate, similar to the chelated supplements magnesium lactate and magnesium aspartate. It is suggested that magnesium chloride be used for horses as the main source of supplemental magnesium for cellular uptake.

What is Magnesium Chloride Hexahydrate (MgCl2.6H20) ?

Magnesium ChlorideThe white crystalline flakes of magnesium chloride hexahydrate are produced from evaporated, naturally- occurring saltwater from which sodium has been removed. Raw material sources include the pure waters of high- altitude salt lakes or deep underground salt deposits, both of which are remnants of prehistoric inland seas.

The magnesium chloride hexahydrate flakes referred to in this article contain over 160mg of elemental magnesium per one gram of flakes, and were obtained from Elektra Life Pty Ltd ( and Whichever brand is used, it is important to ensure the product is certified as Food Grade or free from heavy metal contamination.  Elektra Life Pty Ltd can provide trace mineral analysis down to 10ppb showing no mercury and no lead.

How Can Magnesium Chloride be Used?

All forms of dry magnesium chloride are bitter tasting and likely to be unpalatable for most horses. The unpleasant taste can be masked by dissolving the flakes in water before mixing into a feed. The flakes dissolve quickly in hot water but will also dissolve in cold water. A convenient way to prepare the magnesium chloride solution is fill a large bottle with a measured amount of water, add an appropriate number of tablespoons of flakes, shake well and leave to dissolve. The solution does not need to be prepared fresh each day so a bottle may last several days, depending on the number of horses being fed and the desired strength of the solution.

How Much Can be Fed?

There is no rigid rule that determines how much supplemental magnesium is needed by any individual horse. Just as every person has a need for magnesium that is likely to be different to other people, every horse is also likely to have individual needs. Failure to provide sufficient magnesium for the horse’s daily needs will result initially in a small daily gap between need and intake, which may not be noticed. The daily gap will progressively expand to a whole-body deficit, which may result in negative consequences for the horse’s longterm health and soundness.

Experience with numerous horses indicates that the strength of the magnesium chloride solution can be slowly increased over a couple of months until no more than a slight softening of the manure is observed (assuming visible signs of magnesium deficiency have not been eliminated prior to that point). When that point is reached, the amount of magnesium chloride being fed is reduced to the previous level. This lower level can be maintained until a known increased need arises, for example, impending travel, competition or increase in sugar intake.

Any major changes in weather will have an impact on sugar levels in pasture grasses. Periods of overcast, cloudy, weather can result in lower levels of sugar in some pasture grasses which reduces need for magnesium; a softening of manure consistency may be noticed during this time, indicating magnesium supplementation can be temporarily reduced. Conversely, lack of sunlight can increase pasture potassium levels which may inhibit magnesium absorption, thereby increasing need for magnesium. Horses should be monitored individually.

Sugar levels may increase rapidly with the return of warm, sunny conditions so it is beneficial to increase magnesium before deficiency signs are obvious. For laminitis- prone horses, delays of even a day or two may result in damage to the lamina that can take weeks or months to repair. Similarly, during drought conditions when there is almost no grass available for grazing, sugars may be very high in what little grass is left; when rain does return the rapid growth of new shoots will very quickly increase the volume of sugar being ingested. Under these conditions, it is advisable to increase magnesium on the day it starts raining, not wait for the new shoots to appear a couple of days later. Helpful information on pasture sugar content can be found in the 2010 RIRDC publication Equine Laminitis, Managing Pasture to Reduce Risk.

It is important for the sugar and starch content of any hard feeds to be kept as low as possible at all times. Magnesium cannot be expected to compensate for the high levels of sugar and starch found in grains, cereals, molasses and other sweet- feeds. Similarly, any hay being fed should ideally be low-sugar grass hay, although this can frequently be difficult to obtain.

Example Only – Suggested Use – Magnesium for Horses – ARTICLES & VIDEOS FEEDING METHODS:
Step 1
Dissolve 15g (1 tbsp) flakes in 150ml water and add 10ml of the resulting solution to each feed, preferably twice daily. Increase by another 10ml every 2 or 3 days until 50ml is being added to each feed. Starting with this very weak solution allows the horse’s body time to adjust to a new source of magnesium. Increasing quantity or strength too quickly may cause scouring.

Step 2
Slowly increase the strength of the solution by increasing the quantity of flakes being dissolved, again increasing the amount given to the horse by 10ml every 2 or 3 days.

Step 3
Continue slowly increasing the strength of the solution over a period of some six weeks or so until signs of deficiency have disappeared, or until a slight softening of the manure is noticed. If this happens, reduce the amount of magnesium chloride fed each day to the previous level, then maintain at this level provided manure consistency is normal.

It is advisable to monitor the horse closely for any signs of returning magnesium deficiency so that the dosage rate can be increased if necessary. When body stores of magnesium have been replenished, it should be possible to reduce the amount fed. As the body can only absorb so much at a time, this may take many months and will depend on the quantity of high-sugar feeds ingested, how much magnesium is excreted and the needs of each individual horse.

Body stores of magnesium cannot be assessed by blood test as only around 1% of body magnesium is found in the blood. Cessation of deficiency signs has been found to be the only reliable way to determine that any individual horse is receiving an adequate daily supply of magnesium from all sources.

How Long Does the ‘Magnesium for Horses Feeding Method’ Take to Work?

The first changes to a quieter, calmer temperament are often seen within a week, with progressive improvements continuing over a couple of months. For laminitis horses, improvements in hoof form and function can take several months to be consistent as the new stronger lamellar connection grows down from the coronet, although improvements in foot comfort can often be seen within a month. Overweight or insulin resistant horses have been seen to lose their grass belly within a month – many of these horses also benefit from receiving a small amount of supplemental chromium. Relaxation of a stiff, braced posture usually occurs after a couple of weeks.

Feeding magnesium twice per day has been found to produce better results than feeding just once per day as the horse is able to absorb a higher overall daily amount. For severe problems, an introductory period of feeding small amounts of magnesium throughout the day may be beneficial, providing there is no intestinal disruption.

Is Anything Else Needed in Addition to Magnesium for Horses?

The majority of horses who are supplemented with magnesium chloride do not need additional sources of vitamins or commercially prepared minerals, although this is dependent on individual horses and living conditions. For more information see the subpages for Feeds, Chromium, Salt, Boron, Iodine and Toxin Binder on

What About Calcium?

Despite the need for calcium being heavily promoted, many horses only start to develop strong feet when dietary calcium is limited. For more information see the subpage for Calcium under the Diet main heading on

Is Magnesium for Horses  Safe?

Many reference sources for both humans and animals indicate that magnesium is not toxic; it is found in abundant quantities throughout the body. The major sign of excess dietary magnesium is diarrhoea or scouring.

Too much magnesium of any form is not desirable but even small amounts of some forms of magnesium, for example magnesium sulphate (Epsom salts) can cause scouring as it acts as an irritant to the intestinal lining. Scouring can also be caused by increasing the strength of the magnesium chloride solution too quickly; as with any new feed, the horse’s body needs time to adjust. If this happens, reduce the amount fed for a few days, or even skip entirely for a couple of days, then start again at a much lower level, working up more gradually.

Important: Supplemental minerals, including magnesium, should not be fed to any horse with existing renal problems. Consult a veterinarian for advice before feeding any minerals to any horse with suspected kidney function issues.

by Pauline Moore
August 2014

This information is intended for educational purposes only.  A veterinarian should be consulted for advice on any health concerns. Laminitis  Laminitis Magnesium for HorsesMagnesium for horses Magnesium for horses magnesium for horses

Sources :
Equine Laminitis, Managing Pasture to Reduce Risk, K. Watts, C. Pollit, RIRDC, 2010 Magnesium Chloride for Health and Rejuvenation, B. Bourke, W. Last, Nexus, 2008 The Magnesium Factor, M. Seelig, A. Rosanoff, Avery, 2003

The Magnesium Miracle, C. Dean, Ballantine, 2008

Building Bone Vitality, A. Lanou, M. Castleman, McGraw Hill, 2009 The Calcium Lie, R. Thompson, In Truth Press, 2008

Rapid Recovery from Major Depression using Magnesium Treatment, G. Eby, K. Eby, 2006 Magnesium and Potassium in LAF, P. Chambers,

Bioavailability of US Commercial Magnesium Preparations, Firoz & Graber, 2001 Magnesium Oxide Bioavailability Update, G. Miller, PhD, Premier Chemicals The Fat Switch, Richard J Johnson, MD, Mercola Books, 2012

Excitotoxins, The Taste That Kills, Russell L Blaylock, MD, Health Press, 1997

Gut & Psychology Syndrome, N. Campbell-­‐McBride, MD, MMedSci (neurology), MMedSci (nutrition), Medinform, 2010

Magnesium transport induced ex vivo by a pharmacological dose of insulin is impaired in non-insulin- dependent diabetes mellitus. Magnes Res. 1995 Dec;8(4):359-66. Hua H, Gonzales J, Rude RK. Department of Medicine, University of Southern California School of Medicine, Los Angeles.

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