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Yeast and Horses

By Eleanor Blazer

It’s alive!! (Sometimes.) Yeast is a live microorganism. There are more than 1,500 types of yeast. Beneficial yeast is used to make bread, alcoholic beverages, nutritional supplements and as an ingredient in probiotics (products used to support digestive health). Other types of yeast can cause infection, are used in scientific research and in the production of ethanol.

The most common yeast used in horse diet supplementation is saccharomyces cerevisiae. The primary reason horses are fed yeast is to increase vitamin B intake, and some believe yeast aids equine digestion. Limited studies, however, to determine if saccharomyces cerevisiae can improve the utilization of nutrients and aid in the breakdown of fiber in the equine digestive system does not give a clear answer.

The studies did not use the same amounts, the same diet, the same classification of horses (age, activity level and health status) or the same period of time during testing. It is evident more research is required. Some improvement was noted when horses fed high-starch and low fiber diets were fed active s. cerevisiae. This diet is not recommended for horses and should be avoided. It makes more sense to eliminate the high starch feeds and increase the fiber portion of the diet

But the horse supplement business is huge and horse owners love to part with their money. Brewer’s yeast contains s. cerevisiae. It is a by-product of making beer. The active cultures are killed during the brewing process. Brewer’s yeast is a good source of B vitamins. It also contains high levels of protein, selenium and chromium. It will not aid in the digestion and utilization of nutrients.

Many commercial horse feed products contain brewer’s yeast as an ingredient. It aids in the palatability of the feed and adds to the nutrient profile. Reputable companies avoid making the statement that brewer’s yeast will improve digestion in the large intestine.
Baker’s yeast or active yeast should not be used as a nutritional supplement. It is derived from the same strain of microorganism, but lacks the beneficial B vitamins. Uncooked baker’s yeast will decrease the levels of B vitamins in the body and adversely disrupt the health of the large intestine.

There are products on the market that offer live yeast cultures. On the label of a product containing live yeast culture will be a number stating the level of colony-forming units (CFU’s). It is the measure of live cells in the supplement. For example, it may state “two billion CFU in a scoop”. There are several challenges when feeding a live yeast culture product.

Confidence in the quality of the product is an issue. Heat and sunlight kills the live cells. Proper shipping and handling procedures must be in place. Having the product sit on a pallet in the hot sun or riding in a non-climate controlled truck will damage the supplement. Despite what the label says, you can’t be sure the product is still active.

Many claims of improvement in digestion are based on studies conducted with cattle. Cattle are foregut fermentaters - the breakdown and utilization of forage occurs before the meal reaches the large intestine. Horses are hindgut fermenters – digestion of forage takes place in the large intestine or cecum. This raises the question – “Does the live yeast culture survive the digestive acids in the equine stomach?” Most equine nutritionists believe it does not.

The bottom line is - use your money to purchase better quality forage and feed plenty of it. If you have any change left over – enjoy your favorite yeast based beverage as you watch your horse eat what is natural.

About the Author: For information about caring for and feeding horses take the online “Nutrition for Performance Horses” taught by Eleanor Blazer. Discounts for CHA members on online courses and they count towards continuing education to keep your instructor certification current. Go to www.horsecoursesonline.com for more information.