UltraCruz Equine Magnesium Plus Supplement for Horses is a palatable, pelleted source of magnesium for horses that may need additional supplementation to their diet. Magnesium (Mg) is an essential mineral that horses require for a multitude of different reasons. It serves as an electrolyte in blood, plays a role in protein synthesis, and is found in hundreds of enzyme reactions. It is also needed for optimal muscle contractions and nerve functions. Horses with low levels of magnesium in their diet may experience muscle pain, work intolerance or fatigue, anxiety/nervousness, hypersensitive skin, irregular heartbeat or tying up. With its effect on so many things, Magnesium is especially important for growing or heavily exercised horses.