Dietary Yeast Has Some Benefits for Horses

Various studies have investigated the benefits of feeding yeast to horses. Among the positive results of dietary yeast supplementation are better digestion of fiber; limitation of undesirable changes in the intestinal ecosystem; and reduction in variations in lactic acid concentrations and pH levels after large grain meals.

In growing horses, yeast increased the digestibility of ADF, NDF, calcium, phosphorus, and zinc. Some studies showed an increase in wither height and weight gain in yeast-supplemented weanlings, though the results of other research did not support these findings. Some research in yearlings indicated yeast supplementation led to higher plasma level of lysine and methionine, supporting the production of muscle tissue. Finally, yeast was linked to a 5 to 15% increase in milk production in mares, with the milk showing higher levels of energy and some amino acids.

A recent study in Argentina examined the effects of Saccharomyces cerevisiae supplementation on the closure of articular growth plates in young horses. Quarter Horse fillies were put into two groups and were given standard diets and either 0 or 20 grams of live yeast daily from 8 to 24 months of age. Growth plate closure was determined by radiographs at 8, 12, and 24 months of age. Blood and urine samples were also analyzed to evaluate bone and mineral metabolism parameters.

Distal metacarpal growth plates were half closed or fully closed in 84% of fillies at 8 months old. By the time the fillies were 24 months old, there was a positive but nonsignificant effect on closure of distal radius growth plates in the live yeast group. Bone markers at 24 months of age did not differ between the two groups, but some individual horses in the yeast group showed positive effects. From this research, it can’t be concluded that live yeast supplementation of foals has any significant effect on skeletal maturation.