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Vitamin A For Horses: Quick Facts - Horse Curator Skip to content
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Vitamin A For Horses: Quick Facts

Vitamin A is one of four fat soluble vitamins.  Fat soluble vitamins are stored within the body’s fat and liver. As a result, toxicity can result if too much Vitamin A is ingested.

Why Vitamin A Is Important For Horses :

  • Vision – it plays a crucial role in preventing night blindness.
  • Helps maintain a healthy and responsive immune system.
  • Plays a vital role in bone growth and healing.
  • Supports epithelial tissues.  Epithelial tissues compose the majority of skin tissue as well as line the body’s organs, cavities, respiratory, urinary, and intestinal tracts.
  • Important for the formation and health of some glands.
  • It plays a role in the formation of new blood cells
  • It is vital for the formation of collagen which is important for tendon, ligament and soft tissue health and repair.
  • Is important for embryo development.
  • Is important  for milk development in lactating mares.

Vitamin A is important for vision and preventing night-blindness in horses.


Signs Of Vitamin A Deficiency In Horses

  • Night blindness
  • Excessive tearing of the eyes
  • Light sensitivity
  • Dry, flaky skin
  • Dry flaky hoofs
  • Dry rough coat
  • Prolonged shedding
  • Diarrhea
  • Respiratory infections
  • Loss of appetite
  • Increase in bone size
  • Poor growth
  • Impaired reproduction

Signs Of Vitamin A Toxicity In Horses

  • Loss of coordination
  • Poor muscle tone
  • Rough coat
  • Appear depressed, lay down a lot
  • Fragile bones
  • Malformed fetuses
  • Sloughing of epithelial tissues
  • Decrease in immune function, prone to sickness and infection

Vitamin A Sources For Horses

Vitamin A is found in fresh leafy forage. Most horses turned out in green grassy pastures maintain their Vitamin A levels through grazing. Good quality fresh alfalfa is also an option for horses in dry paddocks or that are stalled.  It is known that vitamin A depletes quickly once hay is cut. Within 6 months most sources of the vitamin are depleted in baled hay. Cut hay that is left drying in the field or that has been rained upon will have limited quantities and quickly depleting levels of vitamin A.

Many grains are fortified with Vitamin A. As with hay, if the grain is stored for long period, the quantity of vitamin A depletes.

Vitamin A Supplements

Many equine nutritionists agree that Vitamin A is the most common vitamin deficiency in horses. But opinions vary about the need to supplement. Some experts believe that horses turned out in green grassy pastures or paddocks during the active growing seasons of spring and fall store enough Vitamin A in their body fat to carry them through the winter and hot summer months. Others recommend supplements during the extreme hot summer months and during the winter when forage has died.

Opinions are mixed as to whether performance horses and horses carrying a high work load benefit from supplementation.  Many nutritionists believe that if the horse is feed a high quality grain fortified with vitamin A along with good quality hay, additional supplementation is not needed.

The majority of equine nutritionalists agree that supplementation is needed during the a mare’s pregnancy through the time the foal is weaned. Most agree that weanlings and yearlings also need Vitamin A supplements for optimal growth.  Stallions may also benefit from additional supplements during breeding season.

Recommended NCR Daily Requirements of Vitamin A For Horses (2007):

(Note: Equine nutritionists agree that the National Center of Research’s recommendations lean toward the minimal requirements to offset signs of deficiency. For optimal health, some experts recommend higher levels).

  • Maintenance: horses not under heavy work load
    • 1,000 pound (460 kg) adult horse – 13800 I. U.
    • 1,100 pound (500 kg) adult horse – 15000 I. U.
  • Performance and work horses
    • 1,000 lbs. (460 kg) – 20700 I. U.
    • 1,100 lbs. (500 kg) – 22500 I. U.
  • Stallion
    • Not breeding
      • 1,000 lbs. (460) – 13800 I. U.
      • 1,100 lbs. (500 kg) – 15000 I. U.
    • Breeding
      • 1,000 lbs. (460kg ) –  20700 I. U.
      • 1,100 lbs. (500 kg) -22500 I. U.
  • Pregnant and lactating mares
    • 1,000 lbs. (460 kg) – 27600 I. U.
    • 1,100 lbs. (500 kg) – 30000 I. U.
  • Foals
    • 6 months estimated weight 476 lbs. (216 kg) – 9715 I. U.
    • 7 months estimated weight 522 lbs. (237 kgs) – 10665 I. U.
    • 8 months estimated weight 567 lbs. (257 kgs) – 11544 I. U.
    • 9 months estimated weight 606 lbs. (275 kgs) – 12358 I. U.
    • 10 months estimated weight 641 lbs. (291 kgs) – 13112 I. U.
    • 11 months estimated weight 642 lbs. (307 kgs) – 13809 I. U.
    • 12 months estimated weight 708 lbs. (321 kgs) – 14455 I. U.
    • 13 months estimated weight 736 lbs. (334 kgs) – 15052 I. U.
    • 14 months estimated weight 765 lbs. (347 kgs) – 15606 I. U.
    • 15 months estimated weight 789 lbs. (358 kgs) – 16118 I. U.
    • 16 months estimated weight 814 lbs. (369 kgs) – 16592 I. U.
    • 17 months estimated weight 833 lbs. (378 kgs) – 17031 I. U.
    • 18 months estimated weight 853 lbs. (387 kgs) – 17437 I. U.
    • 19 months estimated weight 873 lbs. (396 kgs) – 17814 I. U.
    • 20 months estimated weight 891 lbs. (404 kgs) – 18162 I. U.
    • 21 months estimated weight 906 lbs. (411 kgs) – 18484 I. U.
    • 22 months estimated weight 919 lbs. (417 kgs) – 18782 I. U.
    • 23 months estimated weight 934 lbs. (424 kgs) – 19059 I. U.
    • 24 months estimated weight 946 lbs. (429 kgs) – 19314 I. U.

It is important to remember when considering additional supplementation of vitamins, minerals, electrolytes or amino acids to consider all sources of hay, grain (nearly all grain is fortified) , grazing, and other supplements to ensure proper levels and avoid toxicity.