Magnesium deficiency in horses: Symptoms and Causes

Magnesium serves many important functions in the body, ranging from muscle relaxation to nerve conduction. It is a supporting mineral in close to 350 biochemical processes in the body, including decoding genetic information and performance-enhancing effects in horses. Symptoms of magnesium deficiency in horses serve as an alarming sign and shouldn’t go unnoticed.

What does magnesium do for horses?

Magnesium, a macro mineral in horses, is involved in many body functions. Here are the top 10 benefits of magnesium to horses:

  1. It helps relieve muscle contraction by pushing back calcium and promoting muscle relaxation.
  2. It is important to maintain the ion balance at the axon ends of neurons to facilitate nerve conduction.
  3. Magnesium is essential in enhancing the athletic capability of horses by promoting oxygen delivery to muscle fibers.
  4. It helps in the speedy recovery of the horse after strenuous exercises or work by mitigating the pain and cramping of muscles.
  5. Magnesium helps maintain homeostasis in the body, hence it increases tolerance to stress and resistance to diseases.
  6. Magnesium helps horses relieve the symptoms of laminitis.
  7. 60% of a horse’s magnesium stored is in bones. It promotes healthy bones by regulating calcium mobilization.
  8. It helps in the insulin hormone regulation in the blood. Magnesium supplementation in overweight horses can increase insulin sensitivity in horses.
  9. Magnesium contributes to the even distribution of fats in the equine body. It minimizes the chance of crusty neck and fatty pockets.
  10. It helps ease muscle tremors and nervousness, making horses calm.

Symptoms of Magnesium Deficiency in Horses

Magnesium is one of the most common mineral deficiencies occurring in horses. Chronic magnesium deficiency isn’t popular among horses.

You can visualize the changes in the behavior of horses along with the symptoms of magnesium deficiency in horses like-

  • Your horse is never resting. Low magnesium would encourage restlessness and nervousness signs in the horses.
  • Sleep deprivation causes horses to appear fatigued.
  • Low magnesium levels trigger muscle cramps and tetany in horses.
  • The muscles will remain contracted and cause pain after heavy exercise or work.
  • Due to muscle fatigue, the horse won’t do long-period work.
  • Horses become highly sensitive to touch and sound stimuli.
  • Howse will show the history of ‘tying up.’ This condition is also called exertional rhabdomyolysis.’
  • Horses will look irritated and non-obedient.
  • Visible teeth grinding in horses.
  • Horse becomes prone to tendon injuries and diseases because of a decrease in immunity.
  • Horses will show vices. It is always moving, weaving, or head bobbing.
  • Irregular heart rate.
  • Insulin resistance in horses is often associated with low magnesium levels.
  • Demineralization of bones.
  • Poor hoof quality leads to more injuries. Lower magnesium levels are also associated with more chances of laminitis.

What Causes Magnesium Deficiency in Horses?

Have you ever thought about what will happen to your horse if the major source of feed remains the pasture? You will notice a health issue during springtime when the levels of magnesium are low in newly grown grass.

Only a roughage diet does not meet the required magnesium levels in the body and a concentrated diet doesn’t contain enough absorbable magnesium form.

It is not always about feeding. Sometimes your horse’s physiology demands different amounts of magnesium in different growth phases. Also, the magnesium demand of the body increases with the increase in amount of the work.

Pregnant mares or the one nursing a foal require more magnesium.

So, there are enormous chances your horse is running low in magnesium levels in the body needed for the feasibility of different biochemical processes.


Q 1- What does magnesium do for horses?

Ans- Magnesium, a macro mineral in horses, is involved in many body functions. It helps in 300+ biochemical processes, muscle coordination, nerve conduction, insulin regulation, and more.

Q 2- What are the common signs of magnesium deficiency in horses?

Ans- Common magnesium deficiency signs in horses include: Nervousness, fatigue, aggression, muscle cramping, hypersensitive to stimulus, refusal to do more work, abstraction, incoordination, increased chances of laminitis, and more.

Q 3- Do horses need magnesium supplements?

Ans- Scientists have found an adult horses need 7.5 to 10 grams of magnesium per day. If pasture and feed available to the horse cannot meet the demand, we need a good absorbable magnesium supplement to do the work. Magnesium gluconate and magnesium oxide are absorbable magnesium supplements form available.


The requirement of magnesium in horses varies with the change in diet and amount of work. A pregnant mare or a nursing mare would require comparatively more magnesium levels in the body to function.

Horses undoubtedly need magnesium for multiple body functions in horses. Hence, magnesium deficiency can cause severe dysfunction in horses.

Signs of magnesium deficiency in horses include anxiety, hypersensitivity to touch and sound stimuli, irritability, disobedience to do work, weaving vice, head bobbing, prone to injuries, muscle cramping, etc.

We must not ignore these signs. We can cure the deficiency by supplementing the horse with absorbable magnesium form.


Dr Akanksha Agnihotri is another animal lover like you cum veterinarian by profession. She has earned her B.V.Sc & AH from COVS & AH, Jabalpur, India. She has a knack for befriending animals/pets and treating them compassionately. She believes...