Effects of Saccharomyces cerevisiae culture and Saccharomyces cerevisiae live cells on in vitro mixed ruminal microorganism fermentation.

The objective of this study was to examine the effects of a Saccharomyces cerevisiae live cell product and a S. cerevisiae culture product on the in vitro mixed ruminal microorganism fermentation of ground corn, soluble starch, alfalfa hay, and Coastal bermudagrass hay. In the presence of ground corn, neither concentration (0.35 or 0.73 g/L) of S. cerevisiae culture nor live cells had any effect on final pH, H2, CH4, propionate, or butyrate. The S. cerevisiae culture had no effect on acetate, but both concentrations of S. cerevisiae live cells decreased acetate and the acetate:propionate ratio. When soluble starch was the substrate, both concentrations of S. cerevisiae live cells and 0.73 g/L of S. cerevisiae culture decreased the acetate:propionate ratio. Although the treatment effects were not statistically significant, both concentrations of live cells and 0.73 g/L of the culture decreased lactate concentrations compared with the control incubations. When alfalfa hay served as the substrate, neither the S. cerevisiae culture nor the live cells had an effect on propionate, butyrate, or the acetate:propionate ratio. Both concentrations of S. cerevisiae culture decreased the final pH and in vitro dry matter disappearance, and the 0.73 g/L treatment decreased the amount of acetate. However, both treatments of S. cerevisiae live cells increased final pH and decreased acetate and in vitro dry matter disappearance. Neither yeast treatment had much effect on the Coastal bermudagrass hay fermentations. In general, both S. cerevisiae supplements seemed to have similar effects on the mixed ruminal microorganism fermentation.