The effect of substituting different levels of Saccharomyces cerevisiae yeast in the diet of rainbow trout (Oncorhynchus mykiss) to reduce the consumption of fish meal and their effect on growth indices, survival and carcass composition

In the present study, the effect of using different levels of Saccharomyces cerevisiae yeast in the rainbow trout diet was investigated with the aim of reducing the consumption of fish meal. For this purpose, the fish were divided into four treatments (each treatment with three replications) and fed with diets including control diet (no yeast) and yeast levels of 28, 29, 31% and with the same protein ratio. In each experimental unit, 10 fish with an average weight of 48±2 g were placed and fed twice a day at 3% of body weight for 3 weeks. Fish were sampled 21 days after feeding with experimental diets to determine growth indices and carcass composition. The results showed that fish fed a diet containing Saccharomyces cerevisiae had higher weight gain, specific growth rate and daily growth rate than the control group (p<0.05). The highest feed conversion ratio was observed in the control treatment and the lowest in the 28 and 29% yeast treatment. Carcass compositions including protein, fat, moisture, ash and survival rate did not show a significant difference in the experimental diet and the control group (p≥0.05). According to the results of this study, the use of Saccharomyces cerevisiae at the levels of 28 and 29% has a positive effect on growth indices, survival and carcass composition of rainbow trout. Yeast is a suitable alternative to fish meal in rainbow trout diet.