Immune related transcriptional responses and performance of Litopenaeus vannamei post-larvae fed on dietary probiotic PrimaLac®

• PrimaLac® as a commercial multi-strain probiotic improves shrimp immune system.
• Here PrimaLac® increased immune gene expression of Litopenaeus vannamei.
• We observed PrimaLac® effects on digestive enzyme activity in Litopenaeus vannamei.
• Growth performance improved after administrating various levels of PrimaLac®.

The present study investigated the effects of various levels of multi-strain probiotic on the immune related gene expression, digestive enzyme activity, growth performance, body chemical composition and survival of Litopenaeus vannamei post-larvae. After transferring post-larvae of L. vannamei to indoor conditions and subsequent acclimation to laboratory condition for 14 days, the shrimp were fed multi-strain probiotic at four different doses of 0, 0.25, 0.5 and 1.0 g kg−1 for eight weeks. Shrimp fed 0.5 and 1.0 g kg−1 probiotic PrimaLac® exhibited significantly (p < 0.05) higher weight gain, specific growth rate, body crude protein as well as lower FCR compared to other groups. Feeding on 0.5 and 1 g kg−1 dietary multi-strain probiotic significantly (p < 0.05) increased the level of body crude protein. Oral administration of 0.5 and 1.0 g kg−1 multi-strain probiotic significantly (p < 0.05) decreased body crude lipid and body moisture respectively. 30 days after feeding, protease, amylase and lipase activity increased in groups fed 0.5 and 1.0 g kg−1 probiotic PrimaLac®. However, on the 60th day, specific protease and amylase activity in all treatment groups were significantly higher than control group (p < 0.05) but lipase activity was higher (p < 0.05) in groups fed 0.5 and 1.0 g kg−1 multi-strain probiotic. Oral administration of 1.0 g kg−1 probiotic increased (p < 0.05) the level of prophenoloxidase and g-type lysozyme gene on day 30th and 60th after treatment. On day 30th and 60th, penaeidin gene expression was significantly higher in all treatment groups compared to the control group (p < 0.05). In general, findings of this study demonstrated that oral administration of 0.5 and 1.0 g kg−1 multi-strain probiotic improved the performance of the fish and increased the expression of immune related genes.