Digestive enzyme yeast bacteria strain is selected. It is then fermented using aerobic and anaerobic and other fermentation techniques. As a result many important by-products for the digestive system of the animal or fish is produced. Yeacin is feed additive then dried in low temperature. Main function 1) Balance the micro-ecological system of the digestive system in the animal or fish -It helps to improve the animal digestive environment and the types of bacteria structure. It helps to improve the reproduction of the beneficial bacteria and restrict the reproduction of harmful bacterial. -It helps to supply the culture which is essential to the yeast , yeast bacteria and lactobacillus. This will help to increase the effective concentration of yeast bacteria, lactobacillus and cellulose bacteria. 2) Increase the Feed Conversion Ratio -It helps to improve the effective utilization ratio of all kinds of nutrition in daily feed, especially the effective utilization ratio of energy, so that the animal can increase the feed intake and the gain obvious body weight. 3 ) Increase the immunity of animal -It helps to activate the macrophage, enhance the immunity system of animal. Yeacin also helps to secretion of two cell hormones K-1,K-2 to increase the resistance of disease of fish life. -It helps to improve the damage of fish scales when they are being transferred from one to another pond or when harvesting. It will increase the survival rate during transportation.