Does my horse have a magnesium deficiency?

Magnesium is an important element in your horse’s diet. Magnesium is used in muscle contraction and nerve response.  It is also a factor in your horse’s ability to use insulin and maintain proper sugar levels in the body.  

Symptoms of low magnesium

Horse forage like pasture and hay generally have enough magnesium for horses and no supplementation is needed.  But, if the magnesium level in the feed is not sufficient horses can exhibit several different symptoms. Some symptoms of magnesium deficiency are:

• A sore tight back
• An intolerance to being brushed
• Flighty behavior (spooky)
• Excessive sweating 

Spring Grass

Low magnesium is more common in the spring in horses grazing pasture.  Young spring grass is notorious for being low in magnesium.  We often blame hot horses on spring grass with high levels of fructose, but it might actually be the lack of magnesium that is the culprit.  Low magnesium may also be a contributing factor in so many of the grass founder cases we see.  It’s a common understanding that grass high in sugar is dangerous for horses but there needs to be more research done on how magnesium levels also contribute to laminitis in horses. 

Magnesium Supplementation

Did you know that magnesium supplementation in humans can help with insulin resistance, fight depression, reduce migraines, and improve exercise performance? If it can do all this for us, it’s no surprise it can help our horse partners as well.  Most calming supplements out there include magnesium and this only makes sense.  If low magnesium can lead to flighty behavior or over-sensitive muscles, then boosting magnesium levels should improve these behaviors and give the impression the horse is calmer.

My own experience with Magnesium supplementation

Several years ago I was researching sugar content in feeds.  My older mare was barefoot most of her life but always seemed to be tender footed.  Because she was also an easy keeper, I wondered if she suffered from some form of insulin resistance.  In my search for information, I came across an article about the benefits of supplementing horses with magnesium in the spring when the grass is growing quickly.  Deciding to give it a try, I put all of my horses on it.  I was surprised that when trimming them I didn’t see a single sign of spring laminitis.  Usually, at least one horse would show some signs of the lamina stretching in the toe region.  Every horse had very nice and healthy white lines.  Through the years I’ve continued to supplement magnesium while the horses are on pasture and not once have I had an issue.  My mare still has tender feet so I have not solved that mystery but I do feel every horse on my property has benefited from extra magnesium.

How much?

Magnesium is a water-soluble mineral. This means excess magnesium is filtered out by the kidneys.  Diarrhea is the main symptom of too much magnesium.  To supplement your horse with a straight magnesium supplement it is advised to start out with a small amount and raise the dose every few days until you reach your horse’s tolerance level.  If his stools become soft, you know you’ve reached maximum tolerance.  Reduce the dose back down to the last dose the stools were normal and maintain at this level.   

Shopping this article? Here are two magnesium supplements I’ve used. The powdered version is more affordable but messy. On the other hand, the pelleted form is much easier to feed.