Nutrition and growth of rainbow trout (Oncorhynchus mykiss) fed diets supplemented with a synbiotic preparation

Abstract

Abstract This study was carried out in order to assess the effect of inulin and Bacillus on nutrition and growth indices of rainbow trout (Oncorhynchus mykiss). For this purpose, 525 of fish rainbow trout with an average weight of 56.84g ± 4.32 were purchased from fish breeding farm and transferred to the aquaculture department of Shiraz University. After initial adaptation and one week of quarantine, 25 fish were stored in each 500 L polyethylene tank. The duration of the experiment was 60 days. Triplicates were used for each treatment experimental groups included a control (C) without any supplement, treatment (A) with a level of 0.5% inulin, treatment (B) with a level of 1.5% inulin, treatment (D) with a concentration of 103 CFU/g Bacillus, treatment (E) with 106 CFU/g Bacillus, treatment (F) with 103 CFU/g Bacillus and 0.5% inulin and treatment (H) with 106 CFU/g Bacillus and 1.5% inulin. The ratio of feed conversion on 15th, 30th and 60th days in F treatment showed a significant increase compared to other treatments, but on 45th day, the highest rate of this index was observed in treatment H. At the end of the experimental period, treatment D had the highest percentage of specific growth rate with a significant difference compared with other treatments. The highest level of protein efficiency coefficient was observed on 15th, 30th and 60th day of the experiments for the group F and on 45th day in the group containing 103 CFU/g Bacillus. The highest level of fat efficiency ratio was observed in the mentioned days in F treatment. On 45th and 60th day of the experiment, the fat efficiency ratio in treatment D was higher than other treatments. It can be concluded that the simultaneous use of Bacillus and inulin can have the highest positive effects in rainbow trout growth.