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What is Calcium Deficiency ?

As there is a large amount of calcium in the bones of horses, they are a good place for its storage. As the main storage area, should there be a deficiency of calcium in the horse’s diet, calcium will be taken from his bones. In ongoing calcium deficiency, the horse’s bones may weaken.

In horses that are growing, a calcium deficiency can cause problems in growing bone, leading to diseases like osteopenia (where long bones are crooked and joints are enlarged as a result of improper mineralization of osteoid tissue).

A deficiency of calcium can also lead to metabolic bone disease (MBD) which encompasses many bone disorders.

When your horse does not absorb enough calcium to meet his needs he will experience a calcium deficiency; this can lead to a variety of issues, particularly involving his bones.

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Symptoms of Calcium Deficiency in Horses

Should your horse experience calcium deficiency and his bones become demineralized and then weakened, the following may be seen:

  • A decrease in hoof quality
  • His movements are uneven (also called shifting lameness)
  • Hard, bony lumps, likely to experience shin soreness
  • Increased likelihood of fractures under stress
  • Poor quality of teeth; they may be loose and your horse may have a hard time chewing
  • Osteoporosis
  • Arthritis
  • Weight loss even without a change in diet
  • Depression
  • Stiff appearance
  • Shortened gait when trotting
  • Your horse may appear to have a big head; this will occur once calcium taken from the skeleton has gotten to where softer connective tissue replaces the bone matrix, starting with the skull bones
  • As your horse’s jaws swell, those bones and his nasal bone lead to deformity of his head


A calcium deficiency can occur as a result of your horse not taking in enough calcium, however it can also happen when he ingests certain plants that have a high calcium-to-oxalate ratio over a long period of time. These plants include:

  • Kikuyu grass 
  • Buffel grass
  • Pangola grass
  • Green panic grass
  • Para grass
  • Setaria grass

Causes of Calcium Deficiency in Horses

Calcium that comes from the diet of your horse is impacted by several factors. Other minerals may impact calcium’s availability; should there be too much phosphorus in his diet, for example, that mineral interacts with calcium in the small intestine and leads to less calcium being absorbed.

Too much calcium in your horse’s diet can get in the way of his absorbing copper, manganese, zinc and iron. If he has too much zinc in his diet than the zinc may get in the way of his absorbing calcium. It is important that your horse take in not only enough of the vitamins and minerals he needs, but they must be balanced.

Oxalates may also lead to a calcium deficiency. Some plants that your horse may consume in the pasture where he grazes will have high amounts of oxalates. When these interact with calcium they will decrease the amount of calcium that is available to your horse. Plants that contain oxalates include alfalfa, halogeton, shamrock and rhubarb. These plants can lead to a deficiency in calcium if these are the main things your horse eats or if his calcium levels are low.

Diagnosis of Calcium Deficiency in Horses

If your horse has a low blood calcium level (called hypocalcaemia) it will lead to parathyroid hormone being released from the parathyroid gland. This hormone will then trigger the release of calcium from your horse’s bones (in particular the large bones of his head and limbs). The calcium is released into the blood to bring the blood level to normal range for his nerve, heart and muscle function. This is even more apparent when a horse needs a lot of calcium (because of growth, pregnancy, lactation, or heavy sweating).

Should you notice concerning symptoms in your horse, you will want to schedule an appointment with your veterinarian. You will be asked for information regarding the symptoms that you have noticed, when you first noticed them and any changes that have occurred. In addition to a full physical examination, blood and urine tests may be administered. X-rays may be conducted; in cases of calcium deficiency, they may show demineralization of bone mass. 

Treatment of Calcium Deficiency in Horses

As you veterinarian looks to help your horse re-mineralize his bones, calcium supplementation will be provided. In addition, your veterinarian will work with you on ensuring that your horse is also getting the nutrients necessary for the calcium to be absorbed, as calcium on its own won’t help your horse to recover from the deficiency. In addition, your veterinarian will seek to ensure your horse has the proper ratio of calcium to phosphorus (2:1). Supplements are available that will include chelated calcium (already bound to an amino acid so it cannot be taken by oxalates) as well as the nutrients needed for the calcium to be absorbed.

Recovery of Calcium Deficiency in Horses

Preventing calcium deficiency is much easier than trying to resolve the condition. When considering your horse’s diet, make sure that he is consuming items with not only calcium, but the co-factors that are necessary to help him absorb it, to include: magnesium, boron, phosphorous, sodium and Vitamin D.

While your horse is being treated to achieve sufficient levels of calcium and re-mineralize his bones, he should be rested and not be ridden in order to avoid potential fractures.