Influence of traditional Chinese medicine and Bacillus species (TCMBS) on growth, immune response and disease resistance in Nile tilapia, Oreochromis niloticus

Multispecies herbs and probiotic bacteria offered to fish might enhance their immune response and increase disease resistance, but the dose effects of herbal-probiotic application remain unclear. Therefore, the effect of herbal-probiotic mixtures of traditional Chinese medicine (TCM) of composition Astragalus membranaceus, Angelica sinensis, Crataegus hupehensis and probiotic Bacillus species (BS) of composition Bacillus subtilis and Bacillus lincheniformis as natural immunostimulants in tilapia Oreochromis niloticus have been investigated. Fish were randomly divided into four groups: control diet (CT), TCMBS1 [TCM at 3g/kg and BS at 7g/kg], TCMBS2 [TCM at 5g/kg and BS at 5g/kg], TCMBS3 [TCM at 7g/kg and BS at 3g/kg]. Tilapia in the TCMBS3 group showed significant improvement in weight gain, specific growth rate, and lowered feed conversion ratio compared with other treated groups and the control. Concerning immune indexes, all treated groups significantly enhanced lysozyme, superoxide dismutase, catalase, protease and antiprotease activities, with highest values in catalase and antiprotease activities in TCMBS3 compared with control. TCMBS3 demonstrated higher expression of eta-defensin, lysozyme, heat shock protein 70, catalase and transforming growth factor-eta compared with other treated groups or the control group in both mid-intestines and head-kidney. After challenge with Streptococcus agalactiae, the best survival was found in TCMBS3 (97%), followed by TCMBS2 (73%), and TCMBS1 (69%) compared with the CT (35%). Collectively the present results suggest that TCMBS3 dose might potentiate a higher immune response and disease resistance in fish.