Active Feed Dry Yeast is a probiotic feed additive, produced by using a selected yeast strain of Saccharomyces cerevisiae, adding various nutrients and other growth factors, and adopting submerged aerobic fermentation and sterile processing conditions to create the pure and viable yeast product. Active Feed Dry Yeast can enhance animal's appetite and feed digestion and absorption ratio; decrease bacterial number in animal excreta and improve breeding environment; adjust microbial flora balance in intestines and stomach, accelerate reproduction of beneficial bacteria, and decrease bacterial diarrhea.