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Vitamin E in Horse HayBy Kentucky Equine Research Staff · October 9, 2017

Horses depend on their diets for vitamin A and E.  Because horses cannot synthesize these vitamins “in-house,” they must consume them from forages or concentrates. For horses that have access to plentiful amounts of fresh green forage, additional vitamin supplementation is often unnecessary. Shortly after harvesting, however, the amount of vitamins A and E decreases significantly in hay and hay products.

“When feeding a hay-only diet, the vitamin status of the horse should be considered and addressed accordingly with appropriate nutritional supplementation,” said Catherine Whitehouse, M.S., a nutrition advisor for Kentucky Equine Research (KER). “Over time, horses offered hay-only diets may become deficient in vitamin E, which impacts antioxidant protection, immune function, and neuromuscular health.”

Horses that are low or deficient in vitamin E require targeted supplementation. Research has identified that the most bioavailable source of this powerful antioxidant is the natural form rather than the commonly used synthetic form.

Different natural forms are used by manufacturers. Studies have shown that the most effective way of increasing vitamin E status is by using a water-soluble form of natural-source vitamin E, such as Nano-E.

Nano-E uses advanced nanotechnology to create a rapidly available and absorbed source of vitamin E. When selecting a vitamin E supplement or analyzing the ingredients in a product already in use, look for d-alpha tocopherol (natural) rather than dl-alpha tocopherol (synthetic).  

“Other considerations include the impact storage time has on the nutrient content and nutritional value of hay. The longer hay is stored, the greater the amount of nutrients lost. Hay held over for more than a year has considerable less nutritive value than fresh-cut forage,” remarked Whitehouse.

Depending on the nutritional needs of the horse, most hay-only diets should be supplemented with a commercially available product containing appropriate levels of all essential vitamins and minerals. These products differ in the concentration of vitamins and minerals and the daily feeding rate needed to provide the horse with balanced nutrition, according to Whitehouse.

Most horses that can maintain their body weight and condition on only hay have lower energy requirements, which makes offering a ration balancer pellet or concentrated vitamin and mineral supplement like Micro-Max (or Gold Pellet, in Australia) the most appropriate feed choice for meeting requirements.