Effects of bifidobacter probiotic supplement on growth performance and immune system of rainbow trout larvae (Oncorhynchus mykiss)

Today uses of microbial compounds as probiotic are preferred for growth and immune enhancement of fish.The aim of this study was to evaluate effect of different bacterial concentration of Bifidobacterium lactis and Bifidobacterium animalis on growth performance and resistance of rainbow trout against environmental stresses. For this purpose 470 rainbow trout larvae with average mean weight of 0.538±0.197 g (±SD) were obtained and transferred to the laboratory. After 14 days adaptation to the laboratory conditions the fish were randomly divided into four treatments with three replicates (Three experimental treatment and the control). The fish were fed with three concentration of 1×109, 2×109 and 3×109 CFU/100g of probiotic in-feed and the control was fed with diet without probiotic supplementation for 60 days. Length and weight of fish were measured at the beginning and end of study. Also, at the end of study the fish were challenged with environmental stress.The Results showed that the use of the lowest concentration of bacterial increased growth and reduced cortisol in rainbow trout fish blood. Despite of significant growth rate, no significant difference were observed in environmental stresses (P>0.05). Dietary administration of the lowest probiotic concentration could increase the growth and reduced cortisol and ALAT in fish blood.