The yeast has excellent properties is growth fast, high nutritional value. Thrive well in the feed raw materials are cheap grow needs various facter less source energy effectively. There were no easy good industry mutant when cultured in the long time contact, easy to keep, yeast has potential can be used as an animal feed quality. The amino acid lysine And yeast life can still use the accessories to improve the fermentation process. The appropriate level of yeast supplementation in ruminants, at the level of 6 / g / h / day to maintain pH In the proper order on rumen microbial activity. The microbes digest atrophic fibers and yeast is also grow fater to microbes in the rumen. To increase the production efficiency of milk yield and milk composition increase the rate of growth.