The Saccharomyces cerevisiae is known yeast in the brewery and bakery industries. The MOS product which is a derivative of the yeast is used in animal nutrition. Saccharomyces cerevisiae cell wall involves both α-glucans and mannan-proteins. The essential building block for yeast cell wall are polymers of mannan with α (1-2) and α (1-6) bonds and to a less extent α (1-3) bounded side chains (Kogan and Kocher, 2007). 
The diet supplemented with MOS has been reported to have a positive effect regarding body weight, feed efficiency, egg yield, fertility, egg mass and egg hatchability in various poultry species (Guclu, 2011; El-Samee et al., 2012). In another study by Iqbal et al. (2017) who had fed birds with MOS that had significant effects on body and egg mass, egg weight, and egg number and it has shown that feeding MOS as a substitute for antibiotics, as growth enhancer, can positively impact productive traits as well as health aspects in breeders of quail. This can also improve the manifest utilization of energy in feed and improvethe birds feed efficiency that could partially belong to the modulatory impacts of mannan-oligosaccharide on the GIT microflorain broilers (Yang et al., 2008). The current review article discusses the potential aspects of using MOS; including its sources, mode of action and beneficial applications of MOS and its practical uses in the nutrition and production of poultry industry for improving, production, immunity and safeguarding health, among consumers and to prioritize this natural growth promoter as opposed to synthetic antibiotics to cope the medicinal cost in poultry