Objectives: Today, the withdrawal of antibiotics from poultry industry causedpoultry nutritionist to search for the alternatives to conquest the risk factor s of cross-resistance acquisition by harmful bacteria. Prebiotics are defined as nondigestible food ingredients that can be utilized by some of the intestinal microflora, which beneficially affect the host performance. Thus, the purpose of this st udy was to evaluate the effect of a dietary prebiotic (Active MOS) on Japanese quails growth performance. Materials and Methods: A total of 80 seven-days-old unsexed Japanese Quails (Coturnixcoturnix japonica) were used in a completely randomized design with 2 treatments and4 replicates. The birds were randomly allocated to 8 pens (ten birds per pen). The main ingredients of the diets includedcorn and soybean meal.The experimental diets contained 2 levels of a prebiotic (0, 2 g/kg). The prebiotic that was used in this experiment was Active MOS (derived from Saccharomyces cerevisiae, 25 % MOS, 30% BGlucan, Brazil). Birds had access to water and food ad-libitum.The diets were formulated to meet the nutrient requirements of the quail as recommended by NRC (1994). The body weight, feed intake and feed conversion ratio of the birds was measured weekly. Data from this experiment were analyzed by anal ysis of variance using GLM procedures (SAS institute, 2008). Results and Discussion: Birds fed supplemented diets presented lower FCR at all of the experimental periods (P<0.05). Also, feed intake was reduced and body weight gain was increased in the second and thirds weeks of the experiment (P<0.05). Overall, quails fed with prebiotic Active-MOS during 7 to 42 days of age showed better growth performance. However, it was reported that prebiotic supplementation improved feed conversion ratio of broiler breeders numerically, however, the differences were not significant statistically (Hajati et al., 2014). It has been claimed that the benefits of MOS is based on its specific properties such as modification of the intestinal flora, reduction in turnover rate of the intestinal mucosa and modulation of the immune system (Hajati et al., 2012). In conclusion, addition of Active-MOS at the level of 2 g per kilogram of diet improved growth performance of Japanese quails.

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