The effect of probiotics on growth performance and biochemical activity of the shrimp Litopenaeus vannamei was investigated. Lactobacillus sp. was added to shrimp basal diets as probiotics at three concentrations: 5%, 10% and 15% probiotic bacteria was added to basal diet Twelve aquaria with three replicates for each parameter and the Control group were used. After three weeks, shrimp receiving the diets supplemented with probiotics showed significantly better growth performance than those fed the basal diet (Control). The significant (p<0.01) increase in glucose levels were observed in 5% and 10% and 15% groups. Significant difference in triglyceride levels were not observed between control, 5% and 10% probitic treated groups. The 15% group displayed a higher level 43.25 ± 1.71mg/dl and showed significant difference with control. Lactic acid levels were significantly (P<0.01) increased in 10% and15% treated groups. No significant difference was observed in DNA levels but RNA levels were increased in all treated shrimp and significant difference (P<0.01) was observed in 10% group. The 10% probiotic treated group showed highest protein levels and all the treated groups showed significant difference when compared to control.
