Folic acid is one of the brightest new research superstars. It may lift your mood, protect against normal age related memory decline, reduce the risks of certain types of cancers and protect against birth defects.  And it is likely to provide the horse with the same kind of protection. 

 Folic Acid is a B vitamin and is also referred to a Folacin or  Folate.  This vitamin has many functions in the body but, perhaps, the two most important functions are its role in the formation of red blood cells and its involvement in DNA synthesis.

Fortunately for the horse, forages are a dietary source of folic acid.  Growing forages contain 1.5 – 5 mg/kg of folacin.   As this fact would lead one to believe, horses on good pasture have the highest levels of folic acid concentration in the spring and summer.  In one study Thoroughbred broodmares grazing on pasture had serum folate levels at almost two times the normal level.

Evolving as an herbivore which relied on grasses as its main dietary source, the horse faced the challenge of obtaining the necessary vitamins during periods of low grass production.  Nature provided a back-up system.  The horse is blessed with colonies of beneficial bacteria that live in their cecum and colon and produce folic acid.

This system is so efficient that until recently deficiency symptoms have not been described for the horse.  Today, however, certain management techniques have been shown to create a depression in the folic acid levels for some horses.

            Permanently Stalled Horses 

An increasing number of horses find themselves in housed in stalls with little to no opportunity to eat green growing grasses.  These horses may be found living in urban settings on small ranchettes where land and grass are a premium.  They may be housed in at riding facilities especially in northern climates where heated barns and arenas are the order of the day.  They may be at training facilities designed to house racehorses, cutting horses, reining horses, dressage horses, or horses in training for other specialized events.

Horses in these environments are routinely  fed rations composed of hay and grains.  These feeds contain three to five times less folic acid than green plants.  And these level continuous to decrease from the time of harvest till consumption.  For example, year old hay has roughly 50% as much folic acid as fresh cut hay.

Oftentimes, these horses face a double nutritional whammy.  They have limited access to green grass and a rigorous training schedule of forced exercise increases their need for folic acid.

      Horses in Heavy Training

Scientists are just beginning to understand the special role folic acid plays in the metabolism of the performance horse.  It is known that intense forced exercise can decreases blood folate levels.  

One study showed Thoroughbreds in race training had blood folate levels at a significant low level.   Five ng/ml is considered indicative of a borderline folic acid deficiency. The blood folic acid levels of the Thoroughbreds in this study were 3.3 ng/ml.

It is also known that folic acid is lost in the sweat produced through exercise.  Air temperature influences this problem.  Exercise in warmer temperatures increases the amount of sweat produced in any given training session. Therefore the loss of more folic acid.

Exercise also increases the need for more folic acid.  The fitter the animal, the more red blood cells it needs to carry oxygen to the muscles.  Folic acid is a major player in the development of these red blood cells.

Does all this information mean that we need to run out a get a folic acid supplement for horses in these situations?  Probably not!

Folic acid comes in two forms: active and inactive.  The active form is readily available through the diet and can be utilized immediately by the body.  The inactive form which is found in the oral supplements must be activated in the horse's liver before the body can use it.   This system is extremely inefficient.

The best solution for horses which may have these special needs for folic acid is to spend that money on buying the best available feed.  Buy the freshest, greenest hay to be found.  Don’t scrimp on the grain ration.  Buy the top of the line performance feed from a company with a reputation for quality control and a concern for equine nutritional research.  This management plan also usually works for horses on drug therapy.

             Horses on Drug Therapy 

            Horses on drug therapies face a different set of problems. The injections of certain antimicrobial drugs can cause a serious depletion of serum folic acid levels.   Sulfa drugs are a particular culprit.  These drugs work by entering the cell of the bacteria and stopping the cell from manufacturing folic acid.  Without folic acid, the cell dies.

The problem is that the sulfa drugs can’t always tell the good bacteria from the bad bacteria.  Treatment with sulfa drugs reduces the overall production of folic acid for the horse.  That is one of the reasons why treatment with this category of drugs is usually limited to 5 to 7 days.  That is one of the reasons why long term treatment with sulfa drugs is known to cause adverse reactions. 

EPM or Equine Protozoal Myeloencephalitis, presents even more difficult problems.  Two drugs, pyrimethamine  and  sulfadiazine  are commonly used in conjunction to treat EPM.  Both these drugs are known to inhibit folic acid production. 

Treatment regiments for EPM call for the administration of these drugs for up to as long as 3 months.  This treatment has caused the blood folic acid levels for some horses to decrease.  There have also been documented cases of pregnant mares being treated for EPM to deliver deformed foals.

With these facts being known, it would make sense that horses being treated for EPM should be on a folic acid supplement.  However, researchers have conflicting data.

Some researchers do suggest folic acid supplementation for performance horses with EPM but others are hesitant to make any suggestion until further research has been done.  This is because some studies have shown that folic acid supplement may further reduce the blood levels of folic acid.  This is particularly evident in EPM broodmares.

The bottom line:  Folic acid supplementation may only be necessary when folic acid blood values show the horse to be in a deficiency condition.   Quality feed and hay is extremely important for horses in compromised situations.   Supplemental support for the good folic acid bacteria in the form of probiotics may help rebalance and replenish the colonies.

Supplemental folic acid should be provided under “doctor’s orders” and only when a verified deficiency is shown to exit.

copyright, Dr. Jim and Lynda McCall