Magnesium (Mg) is an essential mineral that horses require for proper nerve and muscle function. Magnesium functions as an electrolyte, plays a role in protein synthesis and is involved in over 300 metabolic processes in the horse’s body. It is especially important for growing and heavily exercised horses.

Dosage

Ponies - 20mg daily

Horses - 30mg daily

Horses that are not getting enough magnesium in their diet may be excessively irritable, nervous, or they may chronically tie-up. If your horse experiences thumps (synchronous diaphragmatic flutter) they likely are low in magnesium.

Magnesium deficiency is more likely to occur in the springtime when fast-growing grasses do not accumulate much of this macromineral. Although severe deficiency is rare in horses, suboptimal levels can affect their mood and performance.

Magnesium toxicity is unlikely in horses receiving supplementation because excess amounts are efficiently excreted in the urine. Providing too much, particularly in the form of magnesium sulfate, might cause temporary diarrhea. Magnesium oxide is the recommended form for supplementation.

Magnesium is a macromineral that horses need for optimal muscle function and nerve transmission. It is involved in energy metabolism, enzyme activity and muscle tissue recovery following exercise.

In horses, 60% of magnesium can be found in the bones and the other 40% can be found in extracellular fluids and soft tissues. It is especially important to maintain optimal levels of this mineral in horses that are growing or being heavily exercised.

Horses may not get enough magnesium when their feed levels are low. This is most likely to occur in the spring but can also happen at other times of year, for example if pastures are fertilized to encourage fast growth.

Horses that exercise frequently may have a greater need for magnesium because it is lost in sweat. Young foals also have a higher need to support growth.