With the sun shining again what better time to talk about vitamin D! Here we bring you the facts about vitamin D, including the reason it is often called ‘the sunshine vitamin’…


  1. The horse’s body (as well as your own) converts a form of cholesterol in the skin to vitamin D in the presence of UV light. Consequently, horses may need additional vitamin D to be provided by the diet in winter months or if stabled or rugged for long periods.

  1. Vitamin D is involved in the absorption of calcium and phosphorus and is therefore important for bone health. Feeding the recommended ration of compound feed or balancer alongside suitable forage will ensure your horse’s requirements are met, regardless of their exposure to sunlight.


  1. Vitamin D is actually a hormone because it is produced in one area of the body and acts on another. Although vitamin D is produced in the skin, it is transported to liver and finally the kidneys to be converted to an ‘activated’ form that can be used by the body.

Horse eating grass

  1. Although relatively uncommon, vitamin D deficiency may lead to rickets in young horses or osteomalacia, a condition which results in a weakening of the bones, in adult horses.


  1. Excess vitamin D is stored in the liver and toxicity may lead to the calcification of soft tissue, depression, decreased appetite, weight loss and limb stiffness. Although feeds produced by reputable manufacturers will not lead to toxicity if fed at the recommended ration, the feed with the highest level of vitamin D is not automatically better for your horse.


  1. Vitamin D requirements do not increase as result of workload, pregnancy or lactation!


  1. In foals and growing horses, vitamin D requirements increase with age and at 18 months, are almost 90% higher than adult horses.

For more advice on feeding a balanced diet contact the SPILLERS Care-Line on 01908 226626 or email helpline.horsecareUK@effem.com