In the literature, many studies have reported on the positive effects of yeast culture on milk yield (e.g. Dann et al. 2000) and milk composition of dairy cows and rumen environment (Kung 2001). However, numerous studies have reported no effect of yeast on milk yield and milk composition (Tasdemir and Gorgulu 1998 and Biricik and Yavuz 2001) in dairy cows. Because of these contrast findings, it is necessary to use yeast with other probiotics to see its cooperative effect on milk yield and milk composition.