Getting ideal nutrition year-round from only dietary sources is as difficult for horses as it is for humans. In a perfect setting, a horse would get complete nutrition from high quality grazing and feed rations. In reality, the quality of pastures and hay can be inconsistent. In colder climates, there is a seasonal lack of grazing opportunity. Horses that are recovering from stress or injury, mares that are pregnant, and growing foals need additional supplementation. To be in the peak of health, horses need nutritional supplements that contain specifically formulated vitamins, minerals, and other necessary substances that may be lacking from daily feed rations.

With so many supplements for horses available, it can be helpful to understand the role vitamins play in a horse’s health. Following is a discussion of the major vitamins and their function. Consult with your veterinarian for specific dietary and supplement recommendations for your horse.

Vitamin A is a fat soluble, antioxidant that is needed for healthy skin, hooves, and eyesight. It is also important for healthy digestive, respiratory, and reproductive tissues. A deficiency of Vitamin A can result in impaired growth in young horses, and in adult horses a dry, dull coat with prolonged shedding, diarrhea, anorexia, impaired intestinal absorption, and progressing weakness. Vitamin A can be toxic in too-high doses resulting in fragile bones and an abnormal growth of bone tissue.

The B vitamins include Thiamin (B1), Riboflavin (B2), Pantothenic Acid (B3), Pyroxidene (B6), and Vitamin B-12. These water soluble vitamins are needed to metabolize fats, carbohydrates, and proteins. Though thiamin is the only B complex vitamin deficiency reported in horses, supplementation can be beneficial especially in show horses, race horses, horses that have been stressed or in poor health. Any excess B vitamins are excreted in urine without toxic effects.

Biotin is a coenzyme that plays an essential role in the metabolism of carbohydrates, proteins, and fats. Studies have shown that Biotin supplementation improves hoof quality and strengthened hoof wall.

Vitamin C is a water soluble antioxidant used in the formation of collagen, lysine, and proline. As an antioxidant it fights disease-causing free radicals and studies suggest that supplementation can improve breeding performance. It may also be useful for growth and during periods of stress and high performance.
Vitamin D supplements are typically required by stabled horses that have limited outdoor time. Deficiency results in bone weakness, lameness, and loss of appetite. Vitamin D can be toxic when consumed in excess so talk to your vet before feeding.

Vitamin E is essential for muscle development and function and is important to an efficient immune system. It is also important to red blood cells and oxygen transport, opening blood vessels for free flow of blood. A deficiency of vitamin E results in muscle degeneration and a loss of coordination.