A review of Saccharomyces cerevisiae and the applications of its byproducts in dairy cattle feed: Trends in the use of residual brewer's yeast

This review article aimed to describe the benefits of including different commercial formulations of Saccharomyces cerevisiae – such as yeast fermentation products, active dry yeast, yeast cell wall components, and selenized yeast – in dairy cattle feed. This article also explores the composition of residual brewer's yeast, providing the prospects and restrictions in its use as feed for ruminants. A review according to the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) approach was performed. The bibliographic survey was conducted in Scopus, resulting in a total of 217 documents. This number reduced to 37 papers after the inclusion/exclusion criteria. After reading the full articles, we identified 5 types of S. cerevisiae main products to supplement dairy cows: active dry yeast, S. cerevisiae fermentation product (SCFP), cell wall, selenized yeast, and partially dehydrated brewer's yeast. Considering its composition, studies have suggested the use of residual brewer's yeast as a raw material in the production of supplements to obtain benefits in animal health and production. In contrast, there are challenges in the use of residual brewer's yeast, such as the need for debittering and the yeast's more resistant cell wall. However, the possibility to decrease environmental impact and conceive a sustainable brewering industrial production must be taken into consideration when assessing the use of supplements in feed for ruminants.