Vitamin A for horses

Vitamin A is one of the fat-soluble vitamins, meaning it is stored up in the body. It is potentially the most commonly deficient vitamin for horses that do not receive commercial feeds or do not have access to green forage.

Roughages that are green, leafy and not too old will contain carotene, which can be converted to vitamin A by the horse, but roughages that are bleached, or have been weathered and are dark and dusty will not contain sufficient vitamin content to be considered. If good green forage is available, the horse will generally have sufficient Vitamin A to meet its needs. However, if a horse is fed poor quality roughage, supplemental Vitamin A is needed.

Since so many horses are fed hay that is stored for many months, most all commercially prepared grains contain Vitamin A to help combat this deficiency. It is important to remember that horses can develop a toxicity situation with Vitamin A, if high-potency vitamin supplements are fed on top of an already well-fortified grain base.

Total Dietary (ie. Hay + Grain) Requirements for 1100lb horse, According to 2007 NRC Guidelines:

  • 15,000 IU per day for maintenance horses
  • 22,500 IU per day for moderately active horses
  • 30,000 IU per day for pregnant/lactating mares

Times that are especially critical for additional Vitamin A are the last 90 days of pregnancy and during lactation. High performance horses and weanlings also need additional Vitamin A.

The most common signs of Vitamin A deficiency are dry, scurfy skin and hair coat, and runny eyes and night blindness are other symptoms. A few studies have been done that have shown night blindness can actually be induced by depriving the horse of Vitamin A and then fixed by adding sufficient Vitamin A back in to the diet. Hooves may be dry and scaly. There’s also a slower resistance to respiratory infections, stress and diarrhea. Toxicity symptoms can include dry hair, anemia, and increased bone size.

10 Replies to “Vitamin A for horses”

  1. I have a question about Vit A. I have a mare that foaled on June 6th. Her foal and another mare of mine are showing signs of having a Vit A deficiency, what kind of feed do i look at getting for my herd to help supplement them in this vit? I know now why they are deficient, we have a coverall barn that bleaches all my hay.

    1. Hello Claire, Thanks for the question. Yes, horses can develop toxicity situations with Vitamin A, because it is a vitamin that is stored up in their fat reserves.

      According to 2007 NRC Guidelines, the Total Dietary (ie. Hay + Grain) Requirements for 1100lb horse are:
      15,000 IU per day for maintenance horses
      22,500 IU per day for moderately active horses
      30,000 IU per day for pregnant/lactating mares

      Thank you ~ Gina T.

  2. I have a older miniature horse that is diagnosed with uvitits. I was wondering if I should start giving him vitamin A. He doesn’t weigh anywhere near 1,100 lbs he weighs more 350lbs. What would be the correct daily dosage at his weight?

    1. Hi Monica, We strongly recommend working with your vet before making any dietary changes in relation to a diagnosed condition. Your vet will be able to tell you if dietary changes will affect his specific condition. Thanks! Gina T.

    1. Hello Julie,

      Thanks for the question. This is where tags can be confusing – they require a little math to compare “apples to apples”. This particular supplement is listed in IU/kg. Most feeds list vitamins in IU/lb. You also have to consider that this is a supplement, of which you feed a tiny 1 oz (30 grams) scoop per day. If you follow the math down from the IU/kg to a 30 gram dose, it provides 33,000 IU of Vitamin A per day – provided you follow the one scoop daily dose recommendation.

      Compare this to a feed, which might be listed at 4,000 IU/lb. If you follow the directions and feed 6 lbs per day of the feed, then you are providing 24,000 IU of Vitamin A per day.

      Considering the minimum daily requirement for a 1100 lb horse in maintenance is just 15,000 IU per day, and the same horse in high exercise is around 30,000 IU/day, and you haven’t yet included Vitamin A from forage, most feeds provide plenty of the needed Vitamin A and supplements are not likely required.

      We hope this information is helpful! Thank you ~ Gina T.

    1. Hi Paula,
      Great question! Carrots are a good source of Vitamin A and will contain about 15,000 IU/pound. This is provided as beta carotene, which is why the carrots are orange. The horse converts the beta carotene into Vitamin A. The average carrot weighs about 61 grams or about 2.15 ounces. The average 61 gram carrot also contains about 2.9 grams of sugar, about 4.75% sugar. One reason horses like them!
      Best of luck!
      Roy J.

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