Supplementation of two bacteria isolated from sturgeon gut in the diet of rainbow trout (Oncorhynchus mykiss) larvae to promote resistance when being challenged with stress

Objective: The aim of this study was to isolate the autochthonous probiotic bacteria from digestive tract of Beluga (Huso huso) and persion sturgeon (Acipenser persicus) larvae and inoculation of these bacteria to digestive tract of rainbow trout larvae via supplementation of experimental diets. This study was designed to examine the beneficial affects of these isolated bacteria on health, survival rate and growth parameters in period of experiment and to determine the positive effects of different levels of these bacteria on the increasing of resistance in trout larvae by challenge of thermal, salinity, alkalinity and acidity stress tests in termination of examine. Method & Materials: The Corynebacterium sp and Bacillus mycoides were isolated from the gut of sturgeon and were used with Saccharomyces cerevisiae for supplementation of experimental diets of trout larvae (Oncorhynchus mykiss). The blends of bacteria were supplemented with experimental diets (commercial feed-Biomar) in three concentrations (4.3, 5.3 and 6.3 Log CFU/g of diet) and were fed by larvae in 3 experimental treatments. The control treatment was fed on non-supplemented diet. At the end of the period the fishes were biometeried and tested by thermal (33°C), salinity (40 ppt), alkalinity (pH=12.5) and acidity (pH=2) stresses. Results & Conclusion: The isolated bacteria had the best effects on the promotion of survival and growth performance in trout larvae in comparison with control. The highest final mean weight (1.74 g), specific growth rate (SGR) (9.32), thermal growth coefficient (TGC)(0.122%) and survival rate (96%) were found in treatment A1 (The trout larvae were fed on supplemented diet by blend of isolated bacteria and yeast in level of 4.3 LogCFU/g of feed). The treatments A1, A2 (fed on diet with 5.3 LogCFU/g) had significant difference with control (p<0.05). The results of the challenge tests with stress of alkalinity and acidity indicated that the best survival time was in treatment A1 (275.67 and 374 second, respectively) and total experimental treatments had significant difference with control. No significant difference in salinity challenge test was observed between the treatments. In challenge test of thermal stress, maximum of survival time was obtained in treatment A2 (82 second). The results indicated that the growth performance, health and survival time in challenge tests with stress were positively correlated to isolated bacteria and they had the highest ability to decrease mortality rate in trout larvae.

کلیدواژه ها:

sturgeon ، supplementation ، CFU ، challenge test ، survival