Do Horses Need Magnesium Supplements?

Magnesium has an important role in muscle and nerve function. Horses that are deficient inmagnesium may be unusually spooky and excitable, and they may have muscle tremors or cramping. However, this deficiency is rare because grass and hay normally contain sufficient magnesium to meet the horse’s requirements. Giving a horse too much supplemental magnesium may have no effect at all on nervous behavior or muscle cramping, and may cause serious digestive and metabolic problems.

There are several factors that can decrease the magnesium content of pasture plants. If the soil in a region is deficient in magnesium, growing plants will have a lower content. Lush spring grass has a high moisture content that tends to dilute other nutrients, so each mouthful of this grass will have less magnesium than what would be found in a similar mouthful of summer grass. Diets that are unusually high in potassium can reduce the horse’s ability to absorb magnesium. Finally, intensely exercised horses lose some magnesium in their sweat.

Even if one or more of these conditions exists, horses are not likely to need much, if any, supplementary magnesium. A veterinarian can draw blood for analysis to see if the horse is low in magnesium, and an equine nutritionist can suggest the best way to supplement if this is needed. Because horses are always replenishing magnesium as they graze or eat hay, owners who decide to supplement this nutrient should err on the low rather than the high side to avoid diarrhea and other problems in their horses.

SOURCE: KER