Probiotics are microorganisms that increase the nutritional value of food. They include wide range of micro algae, yeasts, gram-positive and gram negative bacteria. One of the Probiotics which is commonly used in aquaculture is Saccharomyces cerevisiae. Yeasts normally exist in the digestive system of fish and are frequently observed in healthy fish. These microorganisms are generally a good source of protein, nucleotide, vitamins and polysaccharides. This investigation was done to evaluate the probiotic effects of S. cerevisiae on Growth factors carcass composition and food efficiency ratio of Heros severus. Experiment was done in a completely random design in four treatments. Triplicate groups were treated with different levels of S. cerevisiae -Doxal co. Italy-. Treatments were 0.5×1012 -T1-, 1×1012 -T2- and 2×1012 -T3- -CFU- cells per kg diet, and control treatment received no probiotic. The amount of probiotic needed sprayed on the food daily and let it to dry before use. The experiment lasted 30 days.

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