In the present study, fry of O. mykiss fed with different levels of S. cerevisiae had a higher growth rate than those fed with normal artificial food and artificial diet covered by fish oil at the first week (C and D0). Research on the effects of strain of dietary S. cerevisiae and rearing conditions in rainbow trout revealed that supplementation of trout starter diet with S. cerevisiae may be particularly useful to increase fish growth. Moreover, differences in temperature strongly affect fish growth and metabolism (Waché et al., 2006).