Do Horses Need Vitamin D Supplementation?

If you live at northern latitudes, you might lack vitamin D. But what about your horse?
Share
Favorite
Close

No account yet? Register

ADVERTISEMENT

Do Horses Need Vitamin D Supplementation?
Vitamin D is available to your horse in two forms: vitamin D2 (ergocalciferol) found in plants and vitamin D3 (cholecalciferol), which is synthesized in the skin on exposure to sunlight or provided orally in synthetic form. | Photo: iStock
Q: I live at a Northern latitude and my doctor recently diagnosed me as vitamin D deficient. She recommended I take an oral vitamin D supplement. My doctor explained that vitamin D deficiency in people is being more commonly recognized in geographic regions like mine and is due to diminished contact with sunlight for extended periods of the year. This got me wondering, is the same also true for horses? Do horses become vitamin D deficient in winter and should I be supplementing in some way?

A: A review article written by Danish researchers and published in the Journal of Equine Veterinary Science in 2015 summarized our current knowledge about vitamin D and horses. The authors’ take-home message: We “know next to nothing about vitamin D in horses.” This makes it hard to give you a concise answer, but from what we do know I do think that provision of supplemental sources of dietary vitamin D may be of benefit to some horses.

What is Vitamin D?

Vitamin D is available to your horse in two forms: vitamin D2 (ergocalciferol) found in plants and vitamin D3 (cholecalciferol), which is synthesized in the skin on exposure to sunlight or provided orally in synthetic form. Neither of these forms of vitamin D are active and both must go through a number of activation steps before they can influence physiologic functions in the body. The first step occurs in the liver where they are enzymatically hydroxylated to 25-hydroxyvitamin D2 (25OHD2) and 25-hydroxyvitamin D3 (25OHD3). These metabolites then circulate throughout the body in blood plasma.

Almost all organs of the body can further activate these two metabolites to their active form however most of the final conversion occurs in the kidneys. Here 25OHD2 and 25OHD3 are converted to 1,α25-dihydroxyvitamin D2 (1,25(OH)2D2) and 1,α25-dihydroxyvitamin D3 (1,25(OH)2D3) the hormonally active forms of the vitamin that can bind to the vitamin D receptors throughout the body, where they influence physiological functions

Create a free account with TheHorse.com to view this content.

TheHorse.com is home to thousands of free articles about horse health care. In order to access some of our exclusive free content, you must be signed into TheHorse.com.

Start your free account today!

Already have an account?
and continue reading.

Share
Favorite
Close

No account yet? Register

Written by:

Clair Thunes, PhD, is an equine nutritionist who owns Clarity Equine Nutrition, based in Gilbert, Arizona. She works as a consultant with owners/trainers and veterinarians across the United States and globally to take the guesswork out of feeding horses and provides services to select companies. As a nutritionist she works with all equids, from WEG competitors to Miniature donkeys and everything in between. Born in England, she earned her undergraduate degree at Edinburgh University, in Scotland, and her master’s and doctorate in nutrition at the University of California, Davis. Growing up, she competed in a wide array of disciplines and was an active member of the U.K. Pony Club. Today, she serves as the district commissioner for the Salt River Pony Club.

Leave a Reply

Related Articles

Stay on top of the most recent Horse Health news with

FREE weekly newsletters from TheHorse.com

Sponsored Content

Weekly Poll

sponsored by:

How much time do you usually spend grooming your horse?
439 votes · 439 answers

Readers’ Most Popular

Sign In

Don’t have an account? Register for a FREE account here.

Need to update your account?

You need to be logged in to fill out this form

Create a free account with TheHorse.com!