How to Feed a Horse Magnesium

Magnesium is a useful supplement to help your horse remain calm and has some merits in slowing the absorption of sugars in the digestive system. It is vital for the nervous and muscular system to work correctly. It is not a general cure-all however. The most easily absorbed supplement for horses is magnesium oxide, however magnesium supplements are available in several forms - including magnesium sulphate (Epsom salts), calcium Magnesium (dolomite).

Magnesium supplementation is often useful when horses are introduced to new grass or in Spring\Autumn when the flush of grass causes an increased sugar content in the grass. It should not be expected to be used in place of sensible grazing management for your horse or pony.


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    Prepare the amount. A small amount of magnesium, around a tablespoon or so is enough.
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    Mix it in. Magnesium supplements can be easily mixed with your horse's normal feed. If you don't normally feed grain, a small amount of chaff will do.
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    If the horse objects, mix in a little molasses to mask the taste. You can also just add magnesium to a small amount of molasses, applesauce, or other tasty treat to include it in your horse's diet.


  • Care must be taken to evaluate the amount of Mg already available in the horse's diet before adding extra in the belief that it will 'calm' your horse.
  • Always remember that vitamins and minerals need to be 'balanced' feeding too much of one can easily stop others from being absorbed or used by the body
  • There are also calming supplements now available as syringe packs to directly administer a flavoured dose to your horse.
  • It is best not to supplement unless you know that your horse is deficient.
  • Most horses will receive an adequate diet if provided with forage alone
  • The quantity of Mg. in Dolomite is minimal, and a larger percentage of that smallish amount is not assimilated, therefore the calcium balance in the ration must be addressed in relation to phosphorous.
  • Salt licks are available with magnesium in them if you prefer to provide free choice minerals


  • Magnesium is rarely overdosed however over supplementation can interfere with the levels and functions of sodium and potassium. Magnesium deficiency can cause restlessness (hence the use of it as a calming supplement).

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Categories: Horse Feeding