Intensification of livestock production system using high-grain diets become necessary so that, using feed additives and promoters are very important to enhance feed digestion and efficiency to achieve the desired performance and production from the animals. The supplementation of yeast benefits in ruminants could be achieved by several factors such as (1) induce some modifications in microbial population numbers and species, (2) make some favorable changes in the ruminal volatile fatty acids content, (3) have positive effects on rumen ammonia disappearance, (4) have positive effects on rumen pH, (5) promotes metabolism digestion, (6) increase fiber digestibility and modify microbial protein and amino acids in the large intestine, (7) improving the overall intestinal bacteria balance, (8) reducing digestive problems, (9) reducing the risk of acidosis, (10) reducing the humidity of bedding which resulting results in lower stress levels, (11) improving the appetite of animals which leads to increase the feed intake and enhance feed utilization. The benefits above ultimately will lead to enhancement of milk production, improvement of milk quality, mastitis and somatic cell count reduction, more effective immune system. The impact of yeast on animals' performance depends on different factors including animal breed, physiological stage, yeast strain, supplemented dosage, and feeding strategy. With Regarding regarding to the high cost of feed ingredients worldwide, yeast provides a beneficial nutritional strategy, which enhances the feed digestibility and consequently encourages the ruminants' performance in a cost-effective way.