ORIGINAL ARTICLE Influence of traditional Chinese medicine and Bacillus species (TCMBS) on growth, immune response and disease resistance in Nile tilapia, Oreochromis niloticus Emmanuel Delwin Abarike 1,2,3,4,† | Jichang Jian 1,2,3 | Jufen Tang 1,2,3 | Jia Cai 1,2,3,† | Huang Yu 1,2,3 | Chen Lihua 5 | Liang Jun 5 1 College of Fisheries, Guangdong Ocean University, Zhanjiang, China 2 Guangdong Provincial Key Laboratory of Pathogenic Biology and Epidemiology for Aquatic Economic Animals, Zhanjiang, China 3 Guangdong Key Laboratory of Control for Diseases of Aquatic Economic Animals, Zhanjiang, China 4 Department of Fisheries and Aquatic Resources Management, University for Development Studies, Tamale, Ghana 5 Langye Animal Husbandry Company Limited, Gaozhou City, Guangdong province Correspondence Jichang Jian and Jufen Tang, College of Fisheries, Guangdong Ocean University, Huguang Yan East, Zhanjiang 524088, Guangdong Province, China. Emails: jianjc@gdou.edu.cn and tjf10002000@163.com Funding information National Natural Science Foundation of China; Natural Science Foundation of Guangdong Province, Grant/Award Number: 2015A030308020, 2016A030313748; Science and Technology Planning Project of Guangdong Province, Grant/Award Number: 2015A020209181 Abstract 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 mem- branaceus, Angelica sinensis, Crataegus hupehensis and probiotic Bacillus species (BS) of composition Bacillus subtilis and Bacillus lincheniformis as natural immunostimu- lants in tilapia Oreochromis niloticus have been investigated. Fish were randomly divided into four groups: control diet (CT), TCMBS1 [TCM at 3 g/kg and BS at 7 g/ kg], TCMBS2 [TCM at 5 g/kg and BS at 5 g/kg], TCMBS3 [TCM at 7 g/kg and BS at 3 g/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 sig- nificantly enhanced lysozyme, superoxide dismutase, catalase, protease and antipro- tease activities, with highest values in catalase and antiprotease activities in TCMBS3 compared with control. TCMBS3 demonstrated higher expression of beta-defensin, lysozyme, heat shock protein 70, catalase and transforming growth factor-beta 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. KEYWORDS herbal-probiotic mixtures, immune indexes, Streptococcus agalactiae, survival 1 | INTRODUCTION Globally, large-scale tilapia production exposes it to stress and pathogenic disease conditions especially those caused by Streptococcus agalactiae (Aly, Abdel-Galil Ahmed, Abdel-Aziz Gha- reeb, & Mohamed, 2008). Recently, natural immunostimulants includ- ing herbs and probiotic bacteria have been the focus of research (Jagruthi et al., 2014) as suitable alternatives in the prevention and treatment of aquatic animal diseases due to the unsafe nature of antibiotic and chemical use as explained in Heuer et al.(2009). Herbs † These authors contributed to the work equally and should be regarded as co-first authors DOI: 10.1111/are.13691 Aquaculture Research. 2018;1–10. wileyonlinelibrary.com/journal/are © 2018 John Wiley & Sons Ltd | 1