Yeast Supplementation and Fiber Digestion in Horses

Better digestion of fiber has been reported in horses that were supplemented with yeast. In one study, four horses were fed high-fiber or high-starch rations with or without supplementation with yeast (Saccharomyces cerevisiae). The high-fiber and high-starch diets consisted of pelleted feed and wheat straw fed in two meals at fiber-to-starch ratios of 3.5 and 1.0, respectively. After a three-week adaptation period, intestinal contents were collected four hours after meals through fistulas of the cecum and right ventral colon. Contents were analyzed for levels of bacteria and yeast.

Concentrations of lactobacilli were higher in the cecum and colon, and levels of streptococci did not change when dietary starch levels increased. In yeast-supplemented horses, yeast concentrations were higher in the cecum than in the right ventral colon. Concentrations of lactobacilli and lactic acid utilizers were greater in the cecum but the same in the colon of yeast-supplemented horses. A probable explanation is that most enzymes involved in plant cell wall digestion were increased with the addition of yeast.

This article is based in part on the Journal of Animal Science study, “Effect of live yeast culture supplementation on apparent digestibility and rate of passage in horses fed a high-fiber or high-starch diet.”