Whole stillage, a byproduct of ethanol production, is frequently available to beef producers as a potential low-cost feed supplement. The acidic pH of whole stillage is a concern for supplementing high-forage diets and its effects on ruminal fiber digestibility and fermentation are not well characterized. In the current study, increasing whole stillage inclusion (0%, 9.06%, 18.1%, 36.3%) was evaluated in a high-forage diet using an in vitro model to simulate fermentation occurring in the rumen. Increasing whole stillage inclusion decreased in vitro ruminal dry matter and fiber digestion of tall fescue hay. Possible factors contributing to decreased fiber digestion with whole stillage inclusion include the high lipid content, decreased final pH in the in vitro ruminal media, decreased cellulolytic bacteria concentration, and decreased concentrations of branched-chain volatile fatty acids. These results are interpreted to suggest that high levels of dietary whole stillage inclusion could potentially have negative associative effects on the digestion and fermentation of high-forage diets. More research is needed to determine optimal feeding strategies for supplementing liquid distillery byproducts as low-cost alternative feed sources for ruminants.

Read the full article in the Journal of Animal Science.