Yeast Culture: Value-Added Ingredient in Horse Feeds

Feeds are more than a composite of cereal grains, soybean meal, and a dash of vitamins and minerals. Makers of high-quality feeds, like Kentucky Equine Research’s roster of Team Member manufacturers, oftentimes include value-added ingredients in their formulations. These ingredients advance the health and well-being of horses beyond that which is possible with ordinary feeds. Yeast culture is one such ingredient. What is yeast culture? Yeast culture is a mixture of yeast and the media it was grown on, dried in such a way as to preserve the fermenting activity of the yeast.

Researching the effects of yeast culture supplementation in animals began with ruminant nutritionists. As these scientists uncovered the positive effects of yeast culture supplementation in cattle and other ruminants, equine nutritionists began to measure the effects of supplementation in horses. As the advantages came to light, it became clear that yeast culture supplementation improved energy, protein, and mineral digestibility.

Energy production was enhanced in yeast supplemented horses. This was thought to be a ramification of infusing viable, though not necessarily reproductively active, populations of yeast to the horse’s hindgut, thereby boosting the efficiency of the digestive work performed by native intestinal microflora. By stimulating the existent population, an increase in digestion could occur. Such stimulation may also lead to increased reproduction among the native species, resulting in even more microflora that can help digest what is consumed by the horse. Digestion of fiber occurs in the hindgut. When the microflora population is robust and efficient, more fiber can be digested, creating more energy for the horse.

Aside from its advantages in energy production, supplementation with yeast culture has resulted in an increase in protein digestibility. This is especially relevant in the nutrition of young horses, particularly during periods of accelerated growth when certain amino acids are in high demand. In addition to weanlings and yearlings, elevated protein digestibility might be critical for two-year-old horses that are placed in training for either racing or showing.

Absorption of minerals, particularly calcium and phosphorus, increases with yeast culture supplementation. Scientists at Kentucky Equine Research (KER) revealed the importance of yeast culture supplementation to foals and lactating mares, two classes of horses that require the minerals in abundance for proper growth, in the case of foals, and quality milk production, in the case of broodmares.

There’s no question: Research has demonstrated that feeding yeast culture to horses positively affects energy, protein, and mineral nutrition. But how can the stimulatory effects of yeast culture be explained?

“All mechanisms of action are hypothesized. Despite incredible efforts by the research community, no one has been able to prove exactly what is going on,” said Kathleen Crandell, Ph.D., an equine nutritionist with KER.

Based on the literature available, some basic ideas of actions are: Enhancing the activity of the microbial population in the hindgut by (a) providing substrate for improved functioning of the bacteria, (b) balancing the pH to ensure bacterial health, or (c) preparing the digesta for easier breakdown by the bacteria; Reinforcing intestinal immunity by impeding the proliferation and adherence of pathogens like salmonella, clostridia, and shigella and inhibiting production of their toxins; and Augmenting the potential of the enzymes in the small intestine by nurturing the resident enzymes or by stimulating the endogenous production of enzymes. Because the advantages of feeding yeast culture are numerous, horses in various life phases benefit.

Young horses may have improved weight gain, withers height, and feed efficiency. Modest improvements in the growth of weanlings are supported by research when yeast culture is added to the diet. Much might depend on the quality of forage fed; if forage quality is mediocre, a greater response from yeast culture may be expected.

On the opposite end of the age spectrum, aged horses are likely to benefit from yeast culture. As horses age, digestive efficiency of the hindgut is reduced. Because of this, old horses are unable to derive maximal energy from the forage consumed. Yeast culture aids in fiber digestion, thereby supplying the horses with a greater amount of energy to maintain body condition.

Yeast culture can help horses with a range of digestive issues, from poor appetite to intestinal tract damage. Enterocolitis is a severe digestive tract illness thought by many to be brought about by the disruption of the normal microflora in the hindgut. Development of enterocolitis has been associated with dietary changes, prolonged antibiotic use, surgery, and other factors. Yeast culture could assist in rebuilding the population of beneficial microflora in the hindgut, restoring the digestive tract to an efficient state.

Horses on high-grain diets benefit from yeast culture because it might help moderate the swings in pH that often occur when large amounts of grain are consumed. An unsteady hindgut pH is not conducive to a healthy microflora population and may predispose horses to hindgut acidosis. those horses consuming high-grain diets are likely to have stressful lives, competing in demanding events such as racing and traveling from place to place to compete.

Broodmares in late gestation might profit from yeast culture supplementation. The improved digestibility of energy and protein will encourage normal development of the foal and maintenance of body condition during the final months of pregnancy. Continuing supplementation through lactation could improve milk production and foal growth.

What is the best way to supply yeast culture to your horses, on a continual basis or occasionally, only on an as-needed basis? “The studies done on yeast supplementation suggest that continual feeding will supply better results than sporadic feeding,” said Crandell.