Updated: May 8
Folic acid (Vitamin B9) is an essential vitamin in horses and is required for normal red blood cell formation. In horses, "subclinical" deficiencies of serum folate result in mild anemias with lassitude and irritability. In severe folic acid deficiency, anemia due to a reduced number of relatively large red blood cells is found. In horses, folic acid deficiency and resultant anemia may result from pregnancy, hemolytic anemia, or the natural aging process.
Folic acid is richly supplied by green forages and is also synthesized by intestinal bacteria. Based presumably on the assumption that equines may gain adequate supplies from both of these sources, the National Research Council has set no requirements for folic acid in equines.
In contrast with this lack of requirements by the National Research Council, recent research in England strongly suggests that horses in training will benefit from folate supplementation. These investigations came about by a group of trainers wanting to investigate anemia in their thoroughbred stables. The trainers studied vitamin B12 and iron levels in these horses, as well as folate levels in these horses' diets. They found that serum folate levels in grass-fed horses were 11.5ug/ml, whereas the serum folate levels of the stables horses were 7.4ug/ml. This difference was highly significant statistically, and these lower serum folate levels would be considered to be on the borderline of folate deficiency.
In an individual case report, a stabled two-year-old gelding was found to have had a hemoglobin of 11.5gm/100ml, far below the normal 14.5gm/100ml. The horse was also in poor body condition and performed badly during strenuous exercise. The horse had not been fed a diet containing fresh grass for many months. The animal was placed on folic acid, 20mg/day, and within one month its hemoglobin level had risen to more than 14gm/100ml. along with increased serum folate levels. These changes were accompanied by parallel improvements in the animal's condition and performance, despite the fact that he continued on a grass-deficient diet. Based on these studies, these authors concluded that "there may well be a case for routine administration of folic acid to horses which are denied access to fresh grass and particularly if such stabling becomes necessary during pregnancy."
Following up on this early work, the Research Station in Newmarket, studied the serum folate values of Thoroughbred mares at stud, ponies in the grass, and Thoroughbreds in training to race. While the serum folate levels of the mares at stud and the ponies at grass were 10.6 and 10.9 ug/ml respectively, the values in the Thoroughbreds in training were an amazingly low 3.3 ug/ml and showed a very close distribution about the mean. Allen suggested that the very low levels of serum folate in stables horses in training were due to the lack of fresh grass in the diet of these horses combined with the increased loss of folate in the sweat of horses in training since the concentration of folic acid in sweat are about five times those in serum. A further factor was likely to be the increased red blood cell formation and turnover of folate in horses in training. Allen concluded that stables horses, and particular stables racehorses, required folate supplementation during their period of training. The amount of supplementation would appear to be on the order of 15 to 20mg/day, and it would appear wise to include this supplement in the diet of any horses that do not have ready access to fresh grass.
With regard to folic acid supplementation, it is important to remember that folic acid is a DNA precursor and that a deficiency may lead to the reduced formation of more than just red blood cells. Folic acid supplementation is therefore likely to be important in horses recuperating from surgery, or upper respiratory tract or viral infections, where rapid wound healing and cellular regeneration are important. Of further importance is the fact that anabolic steroids and other "blood builders" such as iron injections are much less likely to be effective in the absence of adequate folic acid levels since folic acid is one of the basic building blocks for new blood cell formation.
In conclusion, there is clear-cut evidence of the importance of folic acid in training horses, and that most vitamin and mineral supplements do not contain sufficient amounts of this very important vitamin. It would be highly recommended in supplementing folic acid as a single entity to ensure proper folate levels in your performance horse.
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