摘要
A feeding experiment was conducted to investigate the effect of Bacillus subtilis bacterium and its suitable level on survival and growth rate of juvenile Macrobrachium rosenbergii （de Man） during March 28 to May 28, 2010. A B. subtilis bacterium isolated from chicken intestine was added to commercial prawn feed as a probiotic. Six diets were prepared by soaking prawn feed into the B. subtilis to achieve 10^10, 10^9, 10^8, 10^7 and 106 levels with a non-treated control. After 60 days, the prawns fed diet at level 10^8 showed a higher mean weight gain （593.45 g） or 170.29% increase in growth over control. The mean weight gain showed a decreasing trend as the B. subtilis level decreased from 10^8 to 10^6 and the B. subtilis level increased from 10^8 to 10^10 in the diets. There were significant differences （P 〈 0.05） in weight gain, feed intake, daily growth and feed conversion ratio （FCR） among treated and controlled groups. There were significant differences （P 〈 0.05） among treatments and control in survival rate but no significant differences （P 〉 0.05） in water quality and biochemical composition among treated and controlled groups. Clearly, treated with B. subtilis appeared to enhance growth and survival of M. rosenbergii. It was concluded that the tested strain may be a promising probiotics for M. rosenbergii at a level of 10^8 B. subtilis into the prawn feed.
