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It has been proved that Probiotics applied directly to the water or added as supplement food for shrimp, could positively influence on survival and growth rate. The possible mode of actions could include: inhibition of potential pathogens by competing for nutrients and space; alterations of microbial metabolism by stimulating the host immunity and appetite, improving nutritional value by producing vitamins and enhancing enzymes to breakdown of indigestible components. However, the mode of action in vitro and in vivo of the probiotics is rarely investigated.
The increased shrimp production using intensive systems has been accompanied with bacterial resistance to antibiotics. Probiotics, in this content have become an alternative use for shrimp aquaculture. In the present study, two commercial probiotics (Pediococus acidilactis and a mixture of Bacillus spp.)were supplemented to feed at three different levels, i.e. 0.5, 1.5, and 2.5 ％, to assess the survival, growth and energy budget of juveniles shrimps (Litopenaeus vannamei). Though no marked alterations observed in the morphology of shrimps, significant differences (P<0.05)in survival and growth were found between treatment groups and the control at the end of 32-day feeding trial. Energy consumption in metabolism (R)increased in a dose-dependant manner for P. acidilactis, while decreased for Bacillus spp. Notably, the control showed the highest energy consumption in metabolism. The excretion and the exuviae showed significant differences between treatments and the control (P<0.05).