ABSTRACT
Background: Lactic acid bacteria are the most common class of bacteria used in aquaculture as probiotic
Objectives: In this study the effects of various levels of Lactobacillus casei on the growth performance and digestive enzymes activity of juvenile Shirbot were evaluated. METHODS: Four hundred-eighty juvenile Shirbot weighing 40 g were divided randomly in four treatments [in triplicate]. Treatments of A, B and C were fed with 5x 10[6] CPU g-[1], 5x 10[7] CPU g-[1],5x 10[8] CPU g-[1], respectively for 60 days. Control group was fed with free-probiotic diet. After the period, treatments were fed with free-probiotic diet for 15 days. Growth indices and digestive enzymes were examined on days 0, 30, 60 and 75
Results: In the Treatment B, Specific Growth Ratio, Daily Weight Growth and Relative Growth Rate, after 30 days from the beginning of experiment improved considerably which, compared to control group had significant difference [p<0.05]. Activity of chymotrypsin enzyme in treatment of group B after 30 days and similarly, trypsine in treatment of group C after 30 and 60 days, were increased significantly compared to control group [p<0.05]. In the other points of sampling and enzymes, considerable difference was not seen [p>0.05]
Conclusions: Results showed that 5xl0[7] CFUg[-1] of Lactobacillus casei for 30 days and 5x 10[8] CFUg[-1] for 60 days, are the best doses of probiotic