The practice of adding low levels of non-commensal yeast and fungi to ruminant diets is increasingly gaining acceptance as a means of manipulating rumen fermentation to benefit production. Reported benefits include an increased degradability of forages in the rumen and an improved flow of microbial protein from the rumen (Williams and Newbold, 1990).
Distillery by-products, such as pot ale syrup, are commonly included in ruminant diets as an energy source. However, pot ale syrup contains a substantial number of yeast cells. The aim of the present study was to establish if different yeasts and yeast-containing by-products had similar effects on rumen fermentation to those found with a commercial yeast culture feed additive.
Two commercial Saccharomyces cerevisiae preparations (Alkosel, Alko Biotechnology, Finland and Yea-sacc, Alltech, UK), active dried baker's yeast (United Distillers, UK) and two pot ale syrups from the Inchgower and Dailuaine distilleries were compared for their effects on the fermentation in the rumen simulation technique (Rusitec).