ABSTRACT
The use of probiotic bacteria has been suggested as an important strategy to accomplish reproductible outputs through biocontrol in cultivation systems for marine fish larvae and crustaceans. The bacterial flora in the larval gut originates from bacteria associated with the eggs, the water in the rearing tanks, and the live food. This study was aimed to determine the effect of commercial and Autochthonous probiotics on growth parameters and survival rate of Rainbow trout [Oncorhynchus mykiss] larvae. Trout larvae [85 +/- 4 mg] were fed diets of Biomar. The experimental diets were supplemented with three blends of probiotic bacteria including lactobacillus, commercal Bacillus and isolated sturgeon gut bacillus in three levels [4.30, 5.30 and 6.30 LogCFU/g of feed] and were fed by Rainbow trout [larvae in 9 experimental treatments. The control treatment was fed on nonsupplemented diet. The experiment was carried out in completely random design. At the end of the period the fishes were biometeried and tested by thermal, salinity, alkalinity and acidity stress. The highest specific growth rate, thermal growth coefficient and feed conversion efficiency were found in treatment Al. The treatments A1, A2, B1, B2, L1 andL3 had significant difference with control [p0.05]. The beter feed conversion ratio was obtained in treatment A1 and L3. Inchalleng test of thermal stress, maximum of survival time. was obtained in treatment B 1. The results of the challenge tests with stress of alkalinity and acidity indicated that the best survival time was in treatment Al and total experimeal treatments had significant difference with control [p<0.05]. No significant difference in salinity challenge test was observed between the treatments [p>0.05]