The Importance of B Vitamins for Horses

While there are multiple vitamins horses need each day, B vitamins often are a focus because of their importance. The B vitamins, or the B vitamin complex, are a group of water-soluble vitamins that are critical for blood cell production, cellular and energy metabolism, nerve function, immune system support, and many more important bodily functions.

Which B Vitamins Do Horses Need?

There are 8 specific B vitamins that have been identified as being important to horse health and performance. While some deficiencies of specific B vitamins have not yet been identified (researched) in horses, they are well documented in other species. The important B vitamins for horses are:

  • Vitamin B1 (Thiamine) has a role in the breakdown of sugars/starches and is important to nerve function. In horses, deficiencies have led to anorexia, as well as muscle and heart disorders. Deficiencies in horses that are fed normal diets, in the absence of interfering substances (bracken fern and the antibiotic Amprolium), has not been reported.
  • Vitamin B2 (Riboflavin) helps in breaking down sugars/starches and proteins. It also has a role in immune and nervous system function. Deficiencies can lead to poor hair coats and poor skin has been reported in other species, but not in the horse.
  • Vitamin B3 (Niacin) plays an important role in cellular function. Deficiencies have not been described in the horse.
  • Vitamin B5 (Pantothenic Acid) plays an important role in the breakdown of fats, protein synthesis and immune system function. Deficiencies are rare in other species, but can lead to skin disorders.
  • Vitamin B6 (Pyridoxine) has a role in red blood cell and nerve cell function, as well as energy production. When deficient, nervous system dysfunction and skin disorders can occur.
  • Vitamin B7 (Biotin) plays an important role in the metabolism of fats, sugars/starches, and proteins and has a role in cellular integrity. Biotin has been linked to healthy hooves and skin in horses. Deficiencies have led to poor hair coats, skin, and hooves.  
  • Vitamin B9 (Folate) has an important role in red blood cell production and other cellular function. Folate is very important during pregnancy and rapid growth (foals). Deficiencies have not been described in the horse, except in the presence of long-term use of drugs that impair folate synthesis.
  • Vitamin B12 (Cobalamin) has many important roles, including fat, sugar/starch, and protein metabolism. It is also linked with blood cell production and nerve cell function. Deficiencies can lead to nervous system disorders, like lack of coordination and anemia, but these have not been reported in horses.

Thiamine and Riboflavin are the only two B vitamins with established minimum requirements. A large part of the reason that minimum requirements have not been established for the other B vitamins is because deficiencies are difficult to create in a research setting due to the fact that horses produce their own B vitamins. Conversely, toxicity of B vitamins has not been observed and is generally not a concern in the horse. 

Where Do Horses Get Their B Vitamins?

The B vitamins are classed as “water soluble.” This means that horses cannot store any B vitamins in their tissues - they either utilize the B vitamins in their circulation or excrete what is not used in their urine. Thus, horses require a daily supply of B vitamins for their health and wellbeing.

Interestingly, much of a horse’s minimum daily B vitamin requirements are produced from their hindgut bacteria. As long as the horse has a healthy hindgut and is fed adequate amounts of high-quality forage to keep the good bugs (microbes) “happy”, the microbes will produce enough B vitamins to meet a horse’s daily minimum needs. The only B vitamin daily requirement a horse’s hindgut has difficulty meeting is Vitamin B1. However, in this case and for any B vitamin that microbes struggle to make, a horse can generally meet their daily requirements with quality forage.

The only B vitamin horses are completely dependent on their gut microbes for is Vitamin B12. This means that a horse’s only source of Vitamin B12 is from the hindgut microbes and it cannot be met by feeding forage. However, it is worth noting that for a horse’s gut microbes to be able to make Vitamin B12, they need cobalt. Cobalt is usually found in many forages, except those from cobalt-deficient soils, like those found in Florida or the New England area of the USA. Thus, horses eating forage from these areas would need a cobalt supplement or fed a premium feed that is fortified with cobalt.

Do Horses Need Extra B Vitamins in Their Diets?

Most horses will not need extra B vitamins in their diets to meet their daily minimum requirements. Exceptions are those that may be grazing or eating cobalt-deficient forages, resulting in Vitamin B12 deficiency.  

The question really should be, would it benefit my horse if he is given supplemental B vitamins or fed a quality horse feed that is fortified with B vitamins? The generally accepted answer is “yes.” Much of the literature supports that added B vitamins in the horse’s diet has led to better outcomes, such as maximum performance and health. There are also specific conditions/situations that have demonstrated improved health and performance when B vitamins were supplemented in the diet, including:

  • Horses eating poor quality forage.
  • Horses with a reduced appetite or losing condition.
  • Horses infected with parasites.
  • Horses with poor hindgut health, to include horses being given antibiotics.
  • Aged horses that have reduced digestive efficiency.
  • Horses under stress, including high-performance horses.
  • During dietary changes.

Many commercial horse feeds are fortified with B vitamins. They also will include cobalt, which again, is important for Vitamin B12 synthesis. It would be advised to check a feed’s specifications to see if they are supplying additional B vitamins and cobalt.

Another final tip to be sure your horse is receiving enough B vitamins is to ensure they maintain a healthy hindgut. Check out the following articles for information on supporting your horse’s digestive tract:

If you have any questions or concerns about your horse’s diet, please feel free to contact us for a free, personalized feeding plan!


National Research Council. (2007). Nutrient requirement of horses, 6 th rev. ed. National Academies Press.

Article By: Chris Mortensen, Ph.D.
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