Vitamin D production in horses: sun appears to have little influence!

We learn something new every day too! It is always thought that horses are comparable to humans in many ways, including the production of vitamin D. We also thought this and also that horses that stand in a fly sheet/eczema sheet all summer, for example, can develop a vitamin D deficiency. There was very little scientific study done on this, so the assumption was quickly made that this is similar to humans. But now there has been some research done!

What is the importance of vitamin D?

Vitamin D comes in 2 forms: D2 and D3. Horses get vitamin D2 from their diet (grass, hay, and herbs, for example), while horses produce vitamin D3 themselves. Vitamin D plays an important role in many processes. It is involved in:

• The absorption of calcium and phosphorus

• Supporting the immune system

• Preventing unintended cell division and cell mutations

• Regulating the production of keratin in the skin

• Various neurological functions

The sun may have little influence on vitamin D production

Various studies/opinions assumed that the production of vitamin D in horses is similar to that in humans. That horses need UV light for the production of vitamin D3. There were already a few studies done where no clear differences were seen between horses with blankets and horses without blankets, but no firm conclusions were ever made. A recent study looked at whether sunlight actually has an effect and whether it is necessary to supplement with vitamin D3. Firstly, this study showed that horses have values much lower than humans. In humans, a value below 25 nmol/L is considered a deficiency, while the study showed that the horses were on average at a value of 10.7 nmol/L.

The study also showed that horses that were kept outside all year on grass had undetectable levels of vitamin D3, even in the summer with a lot of sunshine. However, these horses had higher vitamin D2 levels than horses kept in stalls. It was also noticeable that these values were higher in the summer than in the winter.

Is it necessary to supplement vitamin D for horses then?

The studies concluded that horses are actually very capable of obtaining vitamin D from roughage. Especially horses on grass do not need extra vitamin D. Also, the daily values that horses need are much lower than for humans, so a horse needs very little vitamin D per day. And the form in which a horse receives it (D2 or D3) makes little difference to a horse.

Additional research is needed!

These data are based on recent research in horses and provide a lot of information. Of course, more studies will need to follow in order to draw a real, clear conclusion. What about horses that do not have access to grass and stand in blankets on a paddock and receive poor-quality hay? For the majority of horses, it is not necessary to supplement with vitamin D, as long as they receive the right nutrition. We always recommend supplementing with a high-quality balancer so that your horse receives a basic intake of vitamins and minerals.

Source:

https://ker.com/equinews/vitamin-d-biology-cannot-be-extrapolated-from-humans-to-horses/