Did you know that a horse with summer eczema receives less vitamin D? The advice and information platform for all horse and dog enthusiasts.

Two forms of vitamin D

Vitamin D is a fat-soluble vitamin that occurs in 2 forms. There is a plant-based form (D2 - ergocalciferol) and an animal-based form (D3 - cholecalciferol). The plant-based form D2 is obtained by the horse from roughage (grass, hay, and straw). The animal-based form D3 can be produced by the horse itself, but for that, the horse needs UV radiation (sunlight) on its skin. Horses need both forms to meet their vitamin D requirements.

Functions of vitamin D in horses

Vitamin D is involved in many functions in the body. It is also seen more as a hormone than as a vitamin. Many tissues contain vitamin D receptors, which means that vitamin D can influence organs. And that is characteristic of a hormone.

Vitamin D plays an important role in:

the absorption of calcium and phosphate
growth and development
the sensitivity of insulin receptors
the immune system
the function and recovery of muscles

A deficiency in vitamin D can cause problems in many different processes. In horses, for example, this can negatively contribute to insulin resistance, a weakened immune system, or poor bone and teeth quality.

Why do horses with summer eczema have reduced absorption?

In the Netherlands, the period during which there is sufficient sunlight is relatively short. Horse breeds from Northern Europe are genetically adapted to this because they instinctively know that there are only few hours of sunshine. Horses genetically coming from the area around the equator are "used to" having many hours of sunlight. As a result, they utilize UV light less efficiently than the breeds that originally have little sunlight.

However, horses with summer eczema are often covered in the months when the sun is at its strongest, under an eczema blanket + fly mask. These horses therefore receive almost no sunlight on their bodies. And it is precisely that UV radiation on the skin that is very important for the production of vitamin D3. Often the blankets are removed when there is rainy, cloudy weather because there are then fewer insects. But at those times, horses with summer eczema cannot absorb UV radiation. As a result, horses with summer eczema are at risk of receiving too little vitamin D.

Did you know...

Shine and fly sprays also block the absorption of vitamin D? Cholesterol (in skin fat) is necessary for absorption. By using coat sprays, you remove this skin fat, making it less possible to produce vitamin D.
The liver and kidneys play a very important role in vitamin D? The liver and kidneys biologically activate vitamin D so that it can be used by the body. If the liver and/or kidneys are disturbed, this process will not work as well.
Horses can become insulin resistant due to a vitamin D deficiency? Due to the decreased sensitivity of insulin receptors when there is a vitamin D deficiency, horses can develop insulin resistance. Important to keep an eye on in horses with summer eczema.
Artificially dried hay/roughage contains almost no vitamin D3 anymore? Therefore, always opt for sun-dried roughage.

Vitamin D in horse nutrition

If your horse wears a summer eczema blanket, does not get fresh grass, and receives artificially dried roughage? Then it is important to provide the right nutrition with sufficient vitamin D3 content. You do this by supplementing the roughage with a mineral balancer with highly concentrated vitamins and minerals. This is often sufficient for a horse with summer eczema. Do you give concentrate feed? Check the label for grains, starches, and sugars. You do not want these levels to be too high for horses with summer eczema, and often there are lower concentrations of vitamins and minerals in concentrate feed compared to a mineral balancer. You would have to give a lot of concentrate feed to achieve the same amount of minerals and vitamins as with a mineral balancer.

The daily requirement for vitamin D is approximately 4,000 IU. An example of the vitamin D levels in balancers:

Vitalbix Dailycomplete contains 13,000 IU per kilo
Metazoa Superfitt 16,000 IU per kilo
Equilin balancer 20,000 IU per kilo

For a horse of 500 kilograms, you would feed around 300 grams of these balancers. You can see that with these balancers, you easily meet the daily requirement. And especially for horses with summer eczema, it is better to have a bit more than too little. These balancers are all low in starch and sugars and do not contain grains.

For comparison, we have listed the vitamin D content of some (concentrate) feeds. As you can see, these amounts are significantly lower:

Basic feed brand 1: 1,670 IU per kilo
Basic feed brand 2: 4,000 IU per kilo
Basic feed brand 3: 1,250 IU per kilo
Basic feed brand 4: 2,000 IU per kilo

With these basic feeds, you need to feed at least one kilo and with basic feed brand 3 even more than three kilos per day to achieve the same level as the balancer. That is too much since the lowest starch percentage of these feeds is 13%. The highest starch percentage is 28.7%. In comparison, the balancers described above have a maximum of 3% starch and do not contain grains. Do you give concentrate feed? Check the label for the vitamin D content, grains, and starches and compare that with a mineral balancer.

Conclusion:

a mineral balancer with highly concentrated vitamins and minerals is the basic roughage supplement for horses with summer eczema wearing a blanket. Do you feed concentrate feed? Check the label for the amount of vitamin D, starch, and sugar percentage. This is an important key in the management of horses with summer eczema. Of course, some horses may have a higher need for vitamin D. In that case, it is recommended to supplement this based on advice from a therapist.