Vitamin D for Horses

Vitamin D For Horses

Last updated on February 19th, 2021 at 04:52 am

Vitamin D for Horses

If you’ve ever wanted the run down on vitamin D for horses, you are in luck! Today we will be talking all about vitamin D and what it can do for your equine pal. First of all, let’s talk about what vitamin D really is and how it’s available for your horse.

Humans absorb vitamin D through sunlight and supplementation, and it’s the same for horses. Horses have two different forms of vitamin D that they can absorb, either D2 or D3. Vitamin D2 is found in plants while vitamin D3 is synthesized in the skin by exposure to sunlight. We’ll talk more about which form of vitamin D is better for your horse shortly.

But here’s the deal. Vitamin D is in fact a hormone, and your horse will always have enough vitamin D assuming there is plenty of access to sunlight. Without ample sunlight, it is recommended that you supplement vitamin D for your horse. If you don’t, your horse could experience vitamin D deficiency, which can cause bones not to calcify normally. It can even result in rickets in young horses and a metabolic disease known as osteomalacia in adults. 

Which is Better Vit D or Vit d3?

To understand which is better for your horse, vitamin D2 or vitamin D3, it’s important to understand what each of these hormones does and how they occur in nature. Firstly, D3 occurs in animals and D2 occurs in plants. Both forms of vitamins are absorbed in the small intestines of your horse, where they ultimately work to increase calcium absorption, phosphorus absorption, and magnesium absorption. This results in an increase of the releasing of calcium from the bones and a resorption of calcium into the kidney. 

But which one is better? According to theory, most scientists say that D3 is several times more potent as a source of vitamin D than D2. That means your horse needs a lot of exposure to sunlight. Either that, or your horse needs even more D2 to make up for the lack of D3. This can be achieved through eating hays, like orchard grass, which have been dried in the sun and from supplements. 

What Does Vitamin D Do for a Horse?

Vitamin D does a lot for horses, just like it does a lot for people. When your horse is exposed to sunshine, vitamin D3 works to increase its calcium blood levels. Just like how humans thrive on vitamin E for the upkeep of our bones, joints, and muscles, so too do horses. They use vitamin D to have proper muscle functions and enough calcium for healthy bones and joints.

Is Vitamin D Really Necessary?

Vitamin D is absolutely necessary for your horse. It’s critical that every horse has optimal levels of vitamin D to maintain proper health. Without vitamin D, your horse could experience a deficiency, and this can result in a whole lot of nasty problems for the animal, including a reduction in appetite, slow growth, the demineralization of bones, easily fractured bones, possible deformities, and often poor muscle contraction. 

Basically, your horse needs vitamin D to survive and thrive. Because vitamin D plays such an important role with the health of bones and joints, it would be preposterous to neglect such an important hormone.

It’s also important to understand when your horse is not getting enough vitamin D. If your horse is stabled quite frequently, if they are stabled during the day and only let outside at night, if they are bathed too frequently, or if you live in a place with very little sunshine, your horse could develop a deficiency. It’s also common in the winter that horses sometimes lack the Vitamin D they require.

How Much Vitamin D to Give a Horse?

It is generally recommended that the average horse has 6.6 IU of vitamin D per kilogram of their body weight each and every day. That equals roughly 3,300 IU per day for a horse that weighs 500 kilograms (1,100 lbs.). Keep in mind that if your horse is outside for between 5 to 8 hours a day in the sun without some kind of outerwear and not coated in bug spray, the necessary requirements for vitamin D will be fulfilled. 

You should also keep in mind that in hay, there is virtually no vitamin D. If you live in a place without sun or if your horse is unable to get the appropriate amount of this vitamin, it’s absolutely critical that you provide supplementations through proper feed or healthy supplements.

Vitamin D Toxicity in Horses

Believe it or not, vitamin D can be toxic for horses. This does not include sunshine. Horses absolutely cannot overdose on vitamin D3 when they are exposed to the sun. The serious danger comes when the horse is given too much vitamin D through supplements. The first outward signs of vitamin D toxicity, also known as vitamin D toxicosis are decreased appetite, weight loss, depression, and limb stiffness. 

There was one study in which young ponies who were fed 14,000 IU of vitamin D per kilogram of their body weight on a daily basis were afflicted with acute toxicity and serious calcification of the kidney, lungs, heart, and other organs – and the toxicity occurred within just ten days.

This is a pretty horrendous thing to happen, so make sure you never let your horse overdose on vitamin D supplements. Chronic toxicity involves calcification of the kidneys, severe weight loss, and rarefication of bone. This will generally occur when 3,500 IU of vitamin D per kilogram of body weight are ingested daily. Do keep in mind that tolerable doses vary depending on a few different factors, such as the intake of calcium and other nutrients that effect calcium metabolism. These include phosphorus, protein, vitamin A, and magnesium.

The good news here is that vitamin D toxicity is incredibly rare. Considering a horse needs upwards of 3,000 IU of vitamin D to get sick and the recommended dose is 6.6, you would have to try very hard to poison your horse.