Brandenburg’s Tidbits | Did you know @ Vitamin D – “The Sunshine Vitamin”

Enjoying the Morning Sun

Natural Sunlight exposure is the best way to get your daily allowance of Vitamin D.    Doctors say we need approximately 90 minutes a day of natural sunlight exposure to get our recommended dose of this Sunshine Vitamin.   But did you know?    That your horse’s hair coat alone creates such a significant barrier to absorption that it typically takes 5 to 8 hours of exposure to ultra violet light for horses to produce enough vitamin D. Compound that with added blocks like fly spray, coat conditioner, blanket or sheet, or decreased body oils due to bathing, and it becomes apparent that in some cases, horses may not get enough of this vital ingredient.

The main function of both Vitamin D2 and D3 in horses, as well as in humans, is to control the absorption, transport and deposition of calcium and phosphorus. Research indicates that without Vitamin D, horses have difficulty absorbing calcium. If calcium cannot be absorbed through the digestive process, the body might begin to withdraw calcium from bones.  Most processed horse feeds and hay don’t have adequate amounts of Vitamin D.

The health impacts on horses with Vitamin D deficiency can be many. Researchers in equine health believe that Vitamin D deficiencies in horses contribute to such problems as lameness, swollen joints, weak bones and teeth, and a number of cancers, including melanoma.  Other potential health implications for Vitamin D-deficient horses:

  • – Decreased immune system function
  • – Susceptibility to infections because of a weakened immune system
  • – Insulin resistance with blood sugar issues
  • – Tying up disease – rhabdomyolysis, which is essentially a chronic muscle inflammatory condition
  • – Poor muscle recovery time and cramping after exercise
  • – Poor reaction to stress resulting from travel, training and competing
  • – A greater potential to develop laminitis because of the link between laminitis and insulin resistance

Vitamin D is a fat soluble vitamin.   So, you do need to be careful not to overindulge in a good thing.  However, since horse diets are low in D, and the body only makes as much D as it needs, D toxicity is pretty rare in horses.  The only time it would be a concern is if your horse is being fed multiple supplements or fortified feeds containing D.   In that instance, it would be prudent to figure out how much D he is getting, and ensure it is below the upper safe limit of 3,300 IU/day.

The very good news is that sunlight exposure cannot lead to excessive vitamin D production.  So give your horse as much time outdoors, with minimal chemical or physical barriers. Let that vitamin D message do its wonders for the good of your horse.

So let me make this simple.   Just remember to:

  • Give your horse as much outdoor time as possible.
  • Allow pasture grazing, since hay has virtually no vitamin D remaining.
  • Avoid removing oils through excessive bathing with soap. Instead, rinse with plain water.
  • Allow “naked” outdoor time with no coat or fly sprays.

And if this is not feasible, some vitamin D supplementation may be necessary.


I have to give credit where credit is do.  So I need to reference Dr Juliet M. Getty, Ph.D & her blog – .