Re: B vitamins and recommended supplements

Eleanor Kellon, VMD

There are no established dietary requirements for B6, niacin or folic acid so I don't see how they can be called deficient.

Here is some B vitamin information from my NRC Plus course:


Full blown deficiency states related to diet have not been found for any of the B vitamins. In addition to dietary sources, all Bs are synthesized by the intestinal microorganisms.



Functions: Required for normal activity of the enzyme pyruvate dehydrogenase, which is the final step for glucose or pyruvate derived from lactate to enter the Krebs cycle. Also required for some enzymes that transform the carbon backbone of amino acids.

NRC recommendation: Unchanged. 3 mg/kg of DM (dry matter) in the diet, now transformed to 0.06 mg/kg of body weight.

Note: One study suggests that exercising horses have higher requirements, 4+ mg/kg of dietary dry matter. Moderate supplementation of up to 100 mg/day may be advisable for performance horses. Higher dosages of 500 to 1000 mg are sometimes effective in calming nervous horses, but are known to lead to glycogen depletion in other species. High carbohydrate diets increase requirements in other species.

Highest natural sources: Grains (3.5 to 5.7 mg/kg); brans and cereal grain byproducts (8 to 23 mg/kg); high protein seed meals (6.4 to 12 mg/kg); brewer's yeast (95.2 mg/kg). Average of 2.7 mg/kg in hays.



Function: A critical cofactor in enzymes (flavoenzymes) involved in oxidation/reduction actions involving the metabolism of fats, proteins and carbohydrates.

NRC Recommendation: Studies suggest diets containing at least 2 mg/kg of dry matter are adequate.

Highest Natural Sources: Legume hays and grass hays. Cereal grains are lower. All common equine feedstuffs contain greater than 2 mg/kg of dry matter, incorporated into the flavoenzymes of the plant.



Function: Essential for the NAD and NADP enzyme systems, involved in energy generation from fats, carbohydrates and proteins.

NRC Recommendation: None established.

Highest Natural Sources: As for riboflavin, all common feedstuffs contain niacin, although the niacin in seeds and grains may be in an unusable form. Also as for riboflavin, this vitamin is present as a component of the plant's enzyme systems. Niacin can be synthesized from the amino acid tryptophan in the liver.



Function: Cofactor for enzyme systems involved in gluconeogenesis, fatty acid and amino acid metabolism. Involved in insulin sensitivity in people.

NRC Recommendation: None established.

Note: Interestingly enough, a symptom of biotin deficiency in people is burning feet. Biotin is commonly used to enhance hoof growth and improve hoof integrity, at doses of 10+ mg/day, although only improvement in hoof quality is documented by studies.

Highest Natural Sources: Limited information is available. Alfalfa has about 0.49 mg/kg when fresh, which decreases to less than half this amount in baled hays. Concentration is lower in grains.



Folic Acid (supplement form)/Folate (naturally occurring form)

Function: Required for interconversion of amino acids. Very important (with pyridoxine and B-12) when protein turnover is high.

NRC Recommendation: None established.

Note: Folate levels in pasture grasses are adequate to support maintenance, pregnancy and growth. Supplementation of horses at pasture leads to rapid excretion in the urine and no increase in blood levels. However, levels of from 1/2 to 1/3 those seen in pastured levels are observed in stabled horses, lowest when they are in exercise. Comparisons of blood levels in horses on high forage versus high concentrate diets have not been done. Supplementation may be advisable for exercising horses with no access to fresh grass but one study suggests absorption of supplemental folic acid is poor in horses. Red beet powder is a high folate, bioavailable source.

Highest Natural Sources: Grains are a poor source (less than 1 mg/kg DM). Hays contain from 2.5 to 4 mg/kg DM.


B12 (cyanocobalamin)

Functions: Metabolism of fats, carbohydrates and proteins. Interconversion of amino acids.

NRC Recommendation: None

Highest Natural Sources: B12 does not exist in plants. However, it is abundantly synthesized by the microorganisms in the horse's bowel and this is the presumed source.



Functions: Metabolism of fats, proteins and carbohydrates. Interconversion of amino acids.

NRC Recommendation: None established.

Highest Natural Sources: Pasture and hays.


Pantothenic acid

Functions: Essential cofactor for metabolism of all energy sources in the Krebs cycle.

NRC Recommendations: None established.

Highest Natural Sources: This vitamin is present in all common feedstuffs at levels higher than those known to be adequate from feeding trials.

Eleanor in PA 
EC Owner 2001

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